0000950170-24-017421 | 10-K | XBRL Viewer

$ 34,623

$ 157,747

Fair Value, Recurring [Member]

100,276

276,846

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Financial Liabilities Fair Value Disclosure

69,716

82,825

35,119

34,802

Counterparty and Cash Collateral Netting, Assets

^[1]

(22,802)

(136,605)

Counterparty and Cash Collateral Netting, Liabilities

^[1]

(65,157)

(242,044)

Fair Value, Recurring [Member] | Fixed Income Funds [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Fair Value, Recurring [Member] | Equity Funds [Member]

^[2]

1,117

1,267

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Equity investments

^[2]

50,254

54,284

Fair Value, Recurring [Member] | Energy Commodity Derivatives [Member]

^[2]

6,524

6,132

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Counterparty and Cash Collateral Netting, Assets

^[1],[3]

(22,802)

(136,605)

Derivative Asset

^[3]

8,152

9,915

Counterparty and Cash Collateral Netting, Liabilities

^[1],[3]

(65,157)

(242,044)

Derivative Liability

^[3]

34,937

34,747

Fair Value, Recurring [Member] | Natural Gas Exchange Agreements [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Derivative Liability

8,250

Fair Value, Recurring [Member] | Interest Rate Swap [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Derivative Asset

3,667

11,184

Derivative Liability

182

Fair Value, Recurring [Member] | Foreign Exchange Contract [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Derivative Asset, Statement of Financial Position [Extensible Enumeration]

Derivative Asset

$ 43

Investments and Other Noncurrent Assets

Derivative Liability, Statement of Financial Position [Extensible Enumeration]

Investments and Other Noncurrent Assets

Other Liabilities, Noncurrent

Fair Value, Recurring [Member] | Level 1 [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Fair Value, Recurring [Member] | Level 1 [Member] | Fixed Income Funds [Member]

7,641

$ 7,399

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Fair Value, Recurring [Member] | Level 1 [Member] | Equity Funds [Member]

^[2]

1,117

1,267

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Fair Value, Recurring [Member] | Level 2 [Member]

^[2]

6,524

6,132

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Financial Liabilities Fair Value Disclosure

34,623

157,459

92,026

258,824

Fair Value, Recurring [Member] | Level 2 [Member] | Energy Commodity Derivatives [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

^[3]

30,954

146,232

Fair Value, Recurring [Member] | Level 2 [Member] | Interest Rate Swap [Member]

^[3]

91,844

258,769

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

3,667

11,184

Fair Value, Recurring [Member] | Level 2 [Member] | Foreign Exchange Contract [Member]

182

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Fair Value, Recurring [Member] | Level 3 [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Equity investments

50,254

Financial Liabilities Fair Value Disclosure

50,254

54,572

8,250

18,022

Fair Value, Recurring [Member] | Level 3 [Member] | Equity Funds [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Equity investments

^[2]

50,254

54,284

Fair Value, Recurring [Member] | Level 3 [Member] | Energy Commodity Derivatives [Member]

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

^[3]

288

^[3]

$ 8,250

$ 18,022

[1]	The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against payables and receivables for cash collateral held or placed with these same counterparties.
[2]	These assets are included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets.
[3]	The Level 3 energy commodity derivative balances are associated with natural gas exchange agreements.

Balance Sheet Components - Schedule of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Materials and supplies	$ 81,651	$ 75,766
Emission allowances	56,097
Stored natural gas	16,272	26,788
Fuel stock	5,964	5,120
Total	$ 159,984	$ 107,674

Fair Value

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value

NOTE 18. FAIR VALUE

The carrying values of cash and cash equivalents, accounts and notes receivable, accounts payable and short-term borrowings are reasonable estimates of their fair values. Long-term debt (including current portion), finance leases, and long-term debt to affiliated trusts are reported at carrying value on the Consolidated Balance Sheets.

The fair value hierarchy prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to fair values derived from unobservable inputs (Level 3 measurements).

The three levels of the fair value hierarchy are defined as follows:

Level 1 – Quoted prices are available in active markets for identical assets or liabilities. Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis.

Level 2 – Pricing inputs are other than quoted prices in active markets included in Level 1, but which are either directly or indirectly observable as of the reporting date. Level 2 includes financial instruments valued using models or other valuation methodologies. These models are primarily industry-standard models that consider various assumptions, including quoted forward prices for commodities, time value, volatility factors, and current market and contractual prices for the underlying instruments, as well as other relevant economic measures. Substantially all of these assumptions are observable in the marketplace throughout the full term of the instrument, can be derived from observable data or are supported by observable levels at which transactions are executed in the marketplace.

Level 3 – Pricing inputs include significant inputs generally unobservable from objective sources. These inputs may be used with internally developed methodologies that result in management’s best estimate of fair value.

Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy levels. The determination of the fair values incorporates various factors that not only include the credit standing of the counterparties involved and the impact of credit enhancements (such as cash deposits and letters of credit), but also the impact of Avista Corp.’s nonperformance risk on its liabilities.

The following table sets forth the carrying value and estimated fair value of the Company’s financial instruments not reported at estimated fair value on the Consolidated Balance Sheets as of December 31 (dollars in thousands):


	2023				2022
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Long-term debt (Level 2)	$	1,100,000	$	968,893	$	1,113,500	$	966,881
Long-term debt (Level 3)		1,450,000		1,166,512		1,200,000		881,480
Snettisham finance lease obligation (Level 3)		42,495		39,600		45,730		41,700
Long-term debt to affiliated trusts (Level 3)		51,547		46,098		51,547		42,836

These estimates of fair value of long-term debt and long-term debt to affiliated trusts were primarily based on available market information, which generally consists of estimated market prices from third party brokers for debt with similar risk and terms. The price ranges obtained from the third party brokers consisted of par values of 62.73 to 107.245, where a par value of 100.00 represents the carrying value recorded on the Consolidated Balance Sheets. Level 2 long-term debt represents publicly issued

bonds with quoted market prices; however, due to their limited trading activity, they are classified as Level 2 because brokers must generate quotes and make estimates using comparable debt with similar risk and terms if there is no trading activity near a period end. Level 3 long-term debt consists of private placement bonds and debt to affiliated trusts, which typically have no secondary trading activity. Fair values in Level 3 are estimated based on market prices from third party brokers using secondary market quotes for debt with similar risk and terms to generate quotes for Avista Corp. bonds. Due to the unique nature of the Snettisham finance lease obligation, the estimated fair value of these items was determined based on a discounted cash flow model using available market information. The Snettisham finance lease obligation was discounted to present value using the Morgan Markets A Ex-Fin discount rate as published on December 31, 2023.

The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Consolidated Balance Sheets as of December 31, 2023 at fair value on a recurring basis (dollars in thousands):


	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2023
Assets:
Energy commodity derivatives (2)	$	—	$	30,954	$	—	$	(22,802	)	$	8,152
Foreign currency exchange derivatives		—		2		—		—			2
Interest rate swap derivatives		—		3,667		—		—			3,667
Equity investments (3)		—		—		50,254		—			50,254
Deferred compensation assets:
Mutual Funds:
Fixed income securities (3)		1,117		—		—		—			1,117
Equity securities (3)		6,524		—		—		—			6,524
Total	$	7,641	$	34,623	$	50,254	$	(22,802	)	$	69,716
Liabilities:
Energy commodity derivatives (2)	$	—	$	91,844	$	8,250	$	(65,157	)	$	34,937
Interest rate swap derivatives		—		182		—		—			182
Total	$	—	$	92,026	$	8,250	$	(65,157	)	$	35,119

The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Consolidated Balance Sheets as of December 31, 2022 at fair value on a recurring basis (dollars in thousands):


	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2022
Assets:
Energy commodity derivatives (2)	$	—	$	146,232	$	288	$	(136,605	)	$	9,915
Foreign currency exchange derivatives		—		43		—		—			43
Interest rate swap derivatives		—		11,184		—		—			11,184
Equity investments (3)		—		—		54,284		—			54,284
Deferred compensation assets:
Mutual Funds:
Fixed income securities (3)		1,267		—		—		—			1,267
Equity securities (3)		6,132		—		—		—			6,132
Total	$	7,399	$	157,459	$	54,572	$	(136,605	)	$	82,825
Liabilities:
Energy commodity derivatives (2)	$	—	$	258,769	$	18,022	$	(242,044	)	$	34,747
Foreign currency exchange derivatives		—		3		—		—			3
Interest rate swap derivatives		—		52		—		—			52
Total	$	—	$	258,824	$	18,022	$	(242,044	)	$	34,802

(1)

The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against payables and receivables for cash collateral held or placed with these same counterparties.

(2)

The Level 3 energy commodity derivative balances are associated with natural gas exchange agreements.

(3)

These assets are included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets.

The difference between the amount of derivative assets and liabilities disclosed in respective levels in the table above and the amount of derivative assets and liabilities disclosed on the Consolidated Balance Sheets is due to netting arrangements with certain counterparties. See Note 8 for additional discussion of derivative netting.

To establish fair value for energy commodity derivatives, the Company uses quoted market prices and forward price curves to estimate the fair value of energy commodity derivative instruments included in Level 2. In particular, electric derivative valuations are performed using market quotes, adjusted for periods in between quotable periods. Natural gas derivative valuations are estimated using New York Mercantile Exchange pricing for similar instruments, adjusted for basin differences, using market quotes. Where observable inputs are available for substantially the full term of the contract, the derivative asset or liability is included in Level 2.

To establish fair values for interest rate swap derivatives, the Company uses forward market curves for interest rates for the term of the swaps and discounts the cash flows back to present value using an appropriate discount rate. The discount rate is calculated by third party brokers according to the terms of the swap derivatives and evaluated by the Company for reasonableness, with consideration given to the potential non-performance risk by the Company. Future cash flows of the interest rate swap derivatives are equal to the fixed interest rate in the swap compared to the floating market interest rate multiplied by the notional amount for each period.

To establish fair value for foreign currency derivatives, the Company uses forward market curves for Canadian dollars against the U.S. dollar and multiplies the difference between the locked-in price and the market price by the notional amount of the derivative. Forward foreign currency market curves are provided by third party brokers. The Company's credit spread is factored into the locked-in price of the foreign exchange contracts.

Deferred compensation assets and liabilities represent funds held by the Company in a Rabbi Trust for an executive deferral plan. These funds consist of actively traded equity and bond funds with quoted prices in active markets.

Level 3 Fair Value

Natural Gas Exchange Agreement

For the natural gas commodity exchange agreement, the Company uses the same Level 2 brokered quotes described above; however, the Company also estimates the purchase and sales volumes (within contractual limits) as well as the timing of those transactions. Changing the timing of volume estimates changes the timing of purchases and sales, impacting which brokered quote is used. Because the brokered quotes can vary significantly from period to period, the unobservable estimates of the timing and volume of transactions can have a significant impact on the calculated fair value. The Company estimates volumes and timing of transactions based on a most likely scenario using historical data. Historically, the timing and volume of transactions have not been highly correlated with market prices and market volatility.

The following table presents the quantitative information which was used to estimate the fair values of the Level 3 assets and liabilities above as of December 31, 2023 (dollars in thousands):


	Fair Value (Net) at
	December 31, 2023			Valuation Technique	Unobservable Input	Range
Natural gas exchange	$	(8,250	)	Internally derived weighted average cost of gas	Forward purchase prices	$1.64 - $3.07/mmBTU $2.40 Weighted Average
					Forward sales prices	$2.13 - $8.99/mmBTU $5.45 Weighted Average
					Purchase volumes	300,000 - 310,000 mmBTUs
					Sales volumes	75,000 - 310,000 mmBTUs

The valuation methods, significant inputs and resulting fair values described above were developed by the Company's management and are reviewed on at least a quarterly basis to ensure they provide a reasonable estimate of fair value each reporting period.

Equity Investments

The Company has two equity investments measured at fair value on a recurring basis. For one investment, fair value is determined using a market approach, starting with enterprise values from recent market transaction data for comparable companies with similar equity instruments. The market transaction data was used to estimate an enterprise value of the underlying investment and that value was allocated to the various classes of equity via an option pricing model and a waterfall approach. The selection of appropriate comparable companies and the expected time to a liquidation event requires management judgment. The significant assumptions in the analysis include the comparable market transactions and related enterprise values, time to liquidity event and the market discount for lack of liquidity.

For the second investment, the fair value is determined using an income approach utilizing a discounted cash flow model. The model is based on income statement forecasts from the underlying company to determine cash flows for the period of ownership. The model then utilizes market multiples from publicly traded comparable companies in similar industries and projects to estimate the terminal fair value. The market multiples are reduced to reflect the difference in the life cycle between the publicly traded comparable companies and the start-up nature of the investment company. The selection of appropriate comparable companies, market multiples and the reduction to those market multiples requires management judgment. The significant assumptions in the model include the discount rate representing the risk associated with the investment, market multiples and the related reduction to those multiples, revenue forecasts, and the estimated terminal date for the investment.

The following table presents the quantitative information which was used to estimate the fair values of the Level 3 equity investments as of December 31, 2023(dollars in thousands):


	Fair Value at
	December 31, 2023		Valuation Technique	Unobservable Input	Range
Equity investments	$	50,254	Market approach	Comparable enterprise values	$130,000-$388,600 $246,000 Average
				Time to liquidity event	1.5 years
			Discounted cash flows	Revenue market multiples	0.45x to 5.69x Revenue 1.89x Average
				Market exit reduction	50%
				Discount rate	25%
				Annual revenues	$15,000-$245,000
				Terminal date	2027

The following table presents activity for assets and liabilities measured at fair value using significant unobservable inputs (Level 3) for the years ended December 31 (dollars in thousands):


	Natural Gas Exchange Agreement (1)			Equity Investments			Total
Year ended December 31, 2023:
Balance as of January 1, 2023	$	(17,734	)	$	54,284		$	36,550
Total gains or (losses) (realized/unrealized):
Included in regulatory assets		9,238			—			9,238
Recognized in net income		—			(4,323	)		(4,323	)
Purchases and debt conversions		—			3,293			3,293
Settlements		246			—			246
Other		—			(3,000	)		(3,000	)
Ending balance as of December 31, 2023	$	(8,250	)	$	50,254		$	42,004
Year ended December 31, 2022:
Balance as of January 1, 2022	$	(7,771	)	$	—		$	(7,771	)
Transfers in (2)		—			20,902			20,902
Total gains or (losses) (realized/unrealized):
Included in regulatory assets		(4,740	)		—			(4,740	)
Recognized in net income		—			33,382			33,382
Settlements		(5,223	)		—			(5,223	)
Ending balance as of December 31, 2022	$	(17,734	)	$	54,284		$	36,550
Year ended December 31, 2021:
Balance as of January 1, 2021	$	(8,410	)	$	—		$	(8,410	)
Total gains (realized/unrealized):
Included in regulatory assets		4,292			—			4,292
Settlements		(3,653	)		—			(3,653	)
Ending balance as of December 31, 2021	$	(7,771	)	$	—		$	(7,771	)

(1)

There were no purchases, issuances or transfers from other categories of derivatives instruments during the periods presented in the table above.

(2)

The Company elected to account for certain equity investments at recurring fair value in 2022, as such the transfer in represents the value as of the election. See further discussion within Note 7.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Summary of Significant Accounting Policies

NOTE 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Nature of Business

Avista Corp. is primarily an electric and natural gas utility with certain other business ventures. Avista Utilities is an operating division of Avista Corp., comprising its regulated utility operations in the Pacific Northwest. Avista Utilities provides electric distribution and transmission, and natural gas distribution services in parts of eastern Washington and northern Idaho. Avista Utilities also provides natural gas distribution service in parts of northeastern and southwestern Oregon. Avista Utilities has electric generating facilities in Washington, Idaho, Oregon and Montana. Avista Utilities also supplies electricity to a small number of customers in Montana.

AERC is a wholly-owned subsidiary of Avista Corp. The primary subsidiary of AERC is AEL&P, which comprises Avista Corp.'s regulated utility operations in Alaska.

Avista Capital, a wholly owned non-regulated subsidiary of Avista Corp., is the parent company of the subsidiary companies in the non-utility businesses, except AJT Mining Properties, Inc., which is a subsidiary of AERC. See Note 24 for business segment information.

Basis of Reporting

The consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying consolidated financial statements include the Company’s proportionate share of utility plant and related operations associated with its interests in jointly owned plants (see Note 9).

Use of Estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported for assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates include:

•

determining the market value of energy commodity derivative assets and liabilities,

•

pension and other postretirement benefit plan obligations,

•

contingent liabilities,

•

goodwill impairment testing,

•

fair value of equity investments,

•

recoverability of regulatory assets, and

•

unbilled revenues.

Changes in these estimates and assumptions are considered reasonably possible and may have a material effect on the consolidated financial statements and thus actual results could differ from the amounts reported and disclosed herein.

Regulation

The Company is subject to state regulation in Washington, Idaho, Montana, Oregon and Alaska. The Company is subject to federal regulation primarily by the FERC, as well as various other federal agencies with regulatory oversight of particular aspects of its operations.

Depreciation

For utility operations, depreciation expense is estimated by a method of depreciation accounting utilizing composite rates for utility plant. Such rates are designed to provide for retirements of properties at the expiration of their service lives. For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31:


	2023			2022			2021
Avista Utilities		3.52	%		3.50	%		3.54	%
Alaska Electric Light and Power Company		2.78	%		2.78	%		2.77	%

The average service lives for the following broad categories of utility plant in service are (in years):


	Avista Utilities		Alaska Electric Light and Power Company
Electric thermal/other production		26		41
Hydroelectric production		79		42
Electric transmission		50		43
Electric distribution		40		39
Natural gas distribution property		44	N/A
Other shorter-lived general plant		8		18

Allowance for Funds Used During Construction

AFUDC represents the cost of both the debt and equity funds used to finance utility plant additions during the construction period. As prescribed by regulatory authorities, AFUDC is capitalized as a part of the cost of utility plant. The debt component of AFUDC is credited against total interest expense in the Consolidated Statements of Income in the line item “capitalized interest.” The equity component of AFUDC is included in the Consolidated Statements of Income in the line item “other income-net.” The Company is permitted, under established regulatory rate practices, to recover the capitalized AFUDC, and a reasonable return thereon, through its inclusion in rate base and the provision for depreciation after the related utility plant is placed in service. Cash inflow related to AFUDC does not occur until the related utility plant is placed in service and included in rate base.

The WUTC and IPUC have authorized Avista Utilities to calculate AFUDC using its allowed rate of return. To the extent amounts calculated using this rate exceed the AFUDC amounts calculated using the FERC formula, Avista Utilities capitalizes the excess as a regulatory asset. The regulatory asset associated with plant in service is amortized over the average useful life of Avista Utilities' utility plant which is approximately 30 years. The regulatory asset associated with construction work in progress is not amortized until the plant is placed in service.

The effective AFUDC rate was the following for the years ended December 31:


	2023			2022			2021
Avista Utilities		7.03	%		7.12	%		7.19	%
Alaska Electric Light and Power Company		8.61	%		8.08	%		8.90	%

Income Taxes

Deferred income tax assets represent future income tax deductions the Company expects to utilize in future tax returns to reduce taxable income. Deferred income tax liabilities represent future taxable income the Company expects to recognize in future tax returns. Deferred tax assets and liabilities arise when there are temporary differences resulting from differing treatment of items for tax and accounting purposes. A deferred income tax asset or liability is determined based on the enacted tax rates that will be in effect when the temporary differences between the financial statement carrying amounts and tax basis of existing assets and liabilities are expected to be reported in the Company’s consolidated income tax returns. The effect on deferred income taxes from a change in tax rates is recognized in income in the period that includes the enactment date unless a regulatory order specifies deferral of the effect of the change in tax rates over a longer period of time. The Company establishes a valuation allowance when it is more likely than not that all, or a portion, of a deferred tax asset will not be realized. Deferred income tax assets and liabilities and regulatory assets and liabilities are established for income tax benefits flowed through to customers.

The Company has elected to account for transferable tax credits as a component of the income tax provision. The Company recognizes the benefit of production tax credits as a reduction of income tax expense in the period the credit is generated, which corresponds to the period the energy production occurs. The Company applies the deferral method of accounting for investment tax credits (ITCs). Under this method, ITCs are amortized as a reduction to income tax expense over the estimated useful lives of the underlying property that gave rise to the credit.

The Company's largest deferred income tax item is the difference between the book and tax basis of utility plant. This item results from the temporary difference on depreciation expense. In early tax years, this item is recorded as a deferred income tax liability that will eventually reverse and become subject to income tax in later tax years.

The Company did not incur penalties on income tax positions in 2023, 2022 or 2021. The Company would recognize interest accrued related to income tax positions as interest expense or interest income and penalties incurred as other operating expense.

Stock-Based Compensation

The Company issues three types of stock-based compensation awards - restricted shares, market-based awards and performance-based awards. Compensation cost relating to share-based payment transactions is recognized in the Company’s financial statements based on the fair value of the equity instruments issued and recorded over the requisite service period.

The Company recorded stock-based compensation expense (included in other operating expenses) and income tax benefits in the Consolidated Statements of Income of the following amounts for the years ended December 31 (dollars in thousands):


	2023		2022			2021
Stock-based compensation expense	$	7,144	$	7,567		$	4,713
Income tax benefits		1,500		1,589			990
Excess tax benefits (expenses) on settled share-based employee payments		84		(19	)		(909	)

Restricted share awards vest in equal thirds each year over 3 years and are payable in Avista Corp. common stock at the end of each year if the service condition is met. Restricted stock is valued at the close of market of the Company’s common stock on the grant date.

Total Shareholder Return (TSR) awards are market-based awards and Cumulative Earnings Per Share (CEPS) awards are performance awards. Both types of awards vest after a period of 3 years and are payable in cash or Avista Corp. common stock at the end of the three-year period. The method of settlement is at the discretion of the Company and historically the Company has settled these awards through issuance of Avista Corp. common stock and intends to continue this practice. Both types of awards entitle the recipients to dividend equivalent rights, are subject to forfeiture under certain circumstances, and are subject to meeting specific market or performance conditions. Based on the level of attainment of the market or performance conditions, the amount of cash paid or common stock issued will range from 0 to 200 percent of the initial awards granted. Dividend equivalent rights are accumulated and paid out only on shares that have vested and have met the market and performance conditions.

The Company accounts for both the TSR awards and CEPS awards as equity awards and compensation cost for these awards is recognized over the requisite service period, provided the requisite service period is rendered. For TSR awards, if the market condition is not met at the end of the three-year service period, there will be no change in the cumulative amount of compensation cost recognized, since the awards are still considered vested even though the market metric was not met. For CEPS awards, at the end of the three-year service period, if the internal performance metric of cumulative earnings per share is not met, all compensation cost for these awards is reversed as these awards are not considered vested.

The fair value of each TSR award is estimated on the date of grant using a statistical model incorporating the probability of meeting the market targets based on historical returns relative to a peer group. CEPS awards are valued at the close of market of the Company's common stock on the grant date.

The following table summarizes the number of grants, vested and unvested shares, earned shares (based on market metrics), and other pertinent information related to the Company's stock compensation awards for the years ended December 31:


	2023		2022		2021
Restricted Shares
Shares granted during the year		76,806		115,746		62,594
Shares vested during the year		75,007		44,829		34,854
Unvested shares at end of year		152,140		157,860		96,127
Unrecognized compensation expense at end of year (in thousands)	$	3,477	$	3,923	$	2,215
TSR Awards
TSR shares granted during the year		34,912		69,814		64,910
TSR shares vested during the year		61,456		43,730		77,174
TSR shares earned based on market metrics		44,863		48,890		58,652
Unvested TSR shares at end of year		96,915		130,567		107,854
Unrecognized compensation expense at end of year (in thousands)	$	2,235	$	3,533	$	2,653
CEPS Awards
CEPS shares granted during the year		104,685		69,814		64,910
CEPS shares vested during the year		61,456		43,730		38,590
CEPS shares earned based on performance metrics		33,801		—		26,627
Unvested CEPS shares at end of year		161,235		130,567		107,854
Unrecognized compensation expense at end of year (in thousands)	$	2,439	$	2,471	$	1,223

Outstanding restricted, TSR and CEPS share awards include a dividend component paid in cash. A liability for the dividends payable related to these awards is accrued as dividends are announced throughout the life of the award. As of December 31, 2023 and 2022, the Company had recognized a liability of $2.2 million and $1.7 million, respectively, related to the dividend equivalents payable on the outstanding and unvested share grants.

Other Income - Net

Other income - net consisted of the following items for the years ended December 31 (dollars in thousands):


	2023			2022		2021
Interest income	$	5,949		$	1,957	$	1,943
Interest on regulatory deferrals		8,713			1,914		1,206
Equity-related AFUDC		6,886			6,704		7,004
Non-service portion of pension and other postretirement benefit expenses		630			3,037		(1,386	)
Earnings (losses) on investments		(3,227	)		48,492		21,402
Other income		575			613		3,129
Total	$	19,526		$	62,717	$	33,298

Earnings per Common Share

Basic earnings per common share is computed by dividing net income by the weighted-average number of common shares outstanding for the period. Diluted earnings per common share is calculated by dividing net income by diluted weighted-average common shares outstanding during the period, including common stock equivalent shares outstanding using the treasury stock method, unless such shares are anti-dilutive. Common stock equivalent shares include shares issuable under contingent stock awards. See Note 21 for earnings per common share calculations.

Cash and Cash Equivalents

For the purposes of the Consolidated Statements of Cash Flows, the Company considers all temporary investments with a maturity of three months or less when purchased to be cash equivalents.

Allowance for Doubtful Accounts

The Company maintains an allowance for doubtful accounts to provide for estimated and potential losses on accounts receivable. The Company determines the allowance for utility and other customer accounts receivable based on historical write-offs as compared to accounts receivable and operating revenues. Additionally, the Company establishes specific allowances for certain individual accounts. The following table presents the activity in the allowance for doubtful accounts during the years ended December 31 (dollars in thousands):


	2023			2022			2021
Allowance as of the beginning of the year	$	6,473		$	10,465		$	11,387
Additions expensed during the year		6,865			149			9,279
Net deductions (1)		(8,351	)		(4,141	)		(10,201	)
Allowance as of the end of the year	$	4,987		$	6,473		$	10,465

(1)

The higher balance in 2021 is related to COVID-19 forgiveness program. The Company received support from various government agencies in 2023 and 2022 in the amounts of $1.5 million and $6.1 million, respectively, which were applied to overdue customer accounts.

Utility Plant in Service

The cost of additions to utility plant in service, including an allowance for funds used during construction and replacements of units of property and improvements, is capitalized. The cost of depreciable units of property retired plus the cost of removal less salvage is charged to accumulated depreciation.

Asset Retirement Obligations

The Company records the fair value of a liability for an ARO in the period in which it is incurred. When the liability is initially recorded, the associated costs of the ARO are capitalized as part of the carrying amount of the related long-lived asset. The liability is accreted to its present value each period and the related capitalized costs are depreciated over the useful life of the related asset. In addition, if there are changes in the estimated timing or estimated costs of the AROs, adjustments are recorded during the period new information becomes available as an increase or decrease to the liability, with the offset recorded to the related long-lived asset. Upon retirement of the asset, the Company either settles the ARO for its recorded amount or recognizes a regulatory asset or liability for the difference, which will be surcharged/refunded to customers through the ratemaking process. The Company records regulatory assets and liabilities for the difference between asset retirement costs currently recovered in rates and AROs recorded since asset retirement costs are recovered through rates charged to customers (see Note 11 for further discussion of the Company's AROs).

The Company recovers certain asset retirement costs through rates charged to customers as a portion of its depreciation expense for which the Company has not recorded asset retirement obligations. The Company records the amount of estimated retirement costs collected from customers (that do not represent legal or contractual obligations) and includes them as a non-current regulatory liability on the Consolidated Balance Sheets in the following amounts as of December 31 (dollars in thousands):


	2023		2022
Regulatory liability for utility plant retirement costs	$	417,027	$	376,817

Goodwill

Goodwill arising from acquisitions represents the future economic benefit arising from other assets acquired in a business combination not individually identified and separately recognized. In 2023, the Company evaluated goodwill for impairment using a qualitative analysis (Step 0). The Company completed its annual evaluation of goodwill for potential impairment as of November 30, 2023 and determined goodwill was not impaired at that time. No events or circumstances occurred between November 30, 2023 and December 31, 2023 that would more likely than not reduce the fair values of the reporting units below their carrying amounts. As of December 31, 2023 and December 31, 2022, the carrying amount of goodwill was $52.4 million. There are no accumulated impairment losses recognized to date.

Derivative Assets and Liabilities

Derivatives are recorded as either assets or liabilities on the Consolidated Balance Sheets measured at estimated fair value.

The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and costs result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rate cases. The resulting regulatory assets associated with energy commodity derivative instruments are probable of recovery through future rates.

Substantially all forward contracts to purchase or sell power and natural gas are recorded as derivative assets or liabilities at estimated fair value with an offsetting regulatory asset or liability. Contracts not considered derivatives are accounted for on the accrual basis until they are settled or realized unless there is a decline in the fair value of the contract determined to be other-than-temporary.

The Company has multiple master netting agreements with a variety of entities allowing for cross-commodity netting of derivative agreements with the same counterparty (i.e. power derivatives can be netted with natural gas derivatives). In addition, some master netting agreements allow for the netting of commodity derivatives and interest rate swap derivatives for the same counterparty. The Company does not have agreements which allow for cross-affiliate netting among multiple affiliated legal entities. The Company nets all derivative instruments when allowed by the agreement for presentation in the Consolidated Balance Sheets.

Fair Value Measurements

Fair value represents the price that would be received when selling an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. Energy commodity derivative assets and liabilities, deferred compensation assets, some equity investments, as well as derivatives related to interest rate swaps and foreign currency exchange contracts, are reported at estimated fair value on the Consolidated Balance Sheets. See Note 18 for the Company’s fair value disclosures.

Regulatory Deferred Charges and Credits

The Company prepares its consolidated financial statements in accordance with regulatory accounting practices because:

•

rates for regulated services are established by or subject to approval by independent third-party regulators,

•

the regulated rates are designed to recover the cost of providing the regulated services, and

•

in view of demand for the regulated services and the level of competition, it is reasonable to assume that rates can be charged to and collected from customers at levels that will recover costs.

Regulatory accounting practices require certain costs and/or obligations (such as incurred power and natural gas costs not currently reflected in rates, but expected to be recovered or refunded in the future), to be reflected as deferred charges or credits on the Consolidated Balance Sheets. These costs and/or obligations are not reflected in the Consolidated Statements of Income until the period during which matching revenues are recognized. The Company also has decoupling revenue deferrals. See Note 4 for discussion on decoupling revenue deferrals.

If at some point in the future the Company determines it no longer meets the criteria for continued application of regulatory accounting practices for all or a portion of its regulated operations, the Company could be:

•

required to write off its regulatory assets, and

•

precluded from the future deferral of costs or decoupled revenues not recovered through rates at the time such amounts are incurred, even if the Company expected to recover these amounts from customers in the future.

See Note 23 for further details of regulatory assets and liabilities.

Unamortized Debt Expense

Unamortized debt expense includes debt issuance costs that are amortized over the life of the related debt. These costs are recorded as an offset to Long-Term Debt on the Consolidated Balance Sheets.

Unamortized Debt Repurchase Costs

Premiums paid or discounts received to repurchase debt are amortized over the remaining life of the original debt repurchased or, if new debt is issued in connection with the repurchase, these costs are amortized over the life of the new debt. These costs are recovered through retail rates as a component of interest expense.

Appropriated Retained Earnings

In accordance with the hydroelectric licensing requirements of section 10(d) of the Federal Power Act (FPA), the Company maintains an appropriated retained earnings account for earnings in excess of the specified rate of return on the Company's investment in the licenses for its various hydroelectric projects. Per section 10(d) of the FPA, the Company must maintain these excess earnings in an appropriated retained earnings account until the termination of the licensing agreements or apply them to reduce the net investment in the licenses of the hydroelectric projects at the discretion of the FERC. The Company calculates the earnings in excess of the specified rate of return on an annual basis, usually during the second quarter.

The appropriated retained earnings amounts included in retained earnings were as follows as of December 31 (dollars in thousands):


	2023		2022
Appropriated retained earnings	$	59,118	$	57,231

Contingencies

The Company has unresolved regulatory, legal and tax issues which have inherently uncertain outcomes. The Company accrues a loss contingency if it is probable that a liability has been incurred and the amount of the loss or impairment can be reasonably estimated. The Company also discloses loss contingencies that do not meet these conditions for accrual, if there is a reasonable possibility that a material loss may be incurred. As of December 31, 2023, the Company has not recorded significant amounts related to unresolved contingencies. See Note 22 for further discussion of the Company's commitments and contingencies.

Long-Term Debt to Affiliated Trusts - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2023	Dec. 31, 2023	Dec. 31, 2000
Debt Instrument [Line Items]
Payments for repurchase of trust preferred securities			$ 10.0
Avista Corp [Member]
Debt Instrument [Line Items]
Noncontrolling interest, ownership percentage by parent		100.00%
1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] \| Avista Capital II [Member]
Debt Instrument [Line Items]
Junior subordinated debenture issuance date		1997
Principal amount		$ 51.5
Trust Preferred Securities Subject to Mandatory Redemption [Member] \| 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] \| Avista Capital II [Member]
Debt Instrument [Line Items]
Principal amount		$ 50.0
Debt instrument, description of variable rate basis		LIBOR
Debt instrument, basis spread on variable rate		0.875%
Trust Preferred Securities Subject to Mandatory Redemption [Member] \| 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] \| SOFR [Member] \| Avista Capital II [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.137%
Debt instrument basis tenor spread adjustment rate	0.26%
Common Trust Securities [Member] \| 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] \| Avista Capital II [Member]
Debt Instrument [Line Items]
Principal amount		$ 1.5

Summary of Significant Accounting Policies - Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7,144	$ 7,567	$ 4,713
Income tax benefits	1,500	1,589	990
Excess tax benefits (expenses) on settled share-based employee payments	$ 84	$ (19)	$ (909)
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the year	76,806	115,746	62,594
Shares vested during the year	75,007	44,829	34,854
Unvested shares at end of year	152,140	157,860	96,127
Unrecognized compensation expense at end of year (in thousands)	$ 3,477	$ 3,923	$ 2,215
Total Shareholder Return Market-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the year	34,912	69,814	64,910
Shares vested during the year	61,456	43,730	77,174
Shares earned based on market metrics	44,863	48,890	58,652
Unvested shares at end of year	96,915	130,567	107,854
Unrecognized compensation expense at end of year (in thousands)	$ 2,235	$ 3,533	$ 2,653
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the year	104,685	69,814	64,910
Shares vested during the year	61,456	43,730	38,590
Shares earned based on market metrics	33,801		26,627
Unvested shares at end of year	161,235	130,567	107,854
Unrecognized compensation expense at end of year (in thousands)	$ 2,439	$ 2,471	$ 1,223

Document and Entity Information - USD ($)

12 Months Ended

Dec. 31, 2023

Jan. 31, 2024

Jun. 30, 2023

Cover [Abstract]

Entity Registrant Name

AVISTA CORPORATION

Amendment Flag

false

Document Transition Report

false

Document Annual Report

true

Document Type

10-K

Document Period End Date

Dec. 31, 2023

Entity File Number

001-03701

Entity Tax Identification Number

91-0462470

Entity Incorporation, State or Country Code

Entity Address, Address Line One

1411 East Mission Avenue

Entity Address, City or Town

Spokane

Entity Address, State or Province

Entity Address, Postal Zip Code

99202-2600

City Area Code

509

Local Phone Number

489-0500

Title of 12(b) Security

Common Stock

Trading Symbol

AVA

Security Exchange Name

NYSE

Entity Well-known Seasoned Issuer

Yes

Entity Voluntary Filers

Entity Current Reporting Status

Yes

Entity Interactive Data Current

Yes

Entity Filer Category

Large Accelerated Filer

Entity Small Business

false

Entity Emerging Growth Company

false

Document Financial Statement Error Correction [Flag]

false

Entity Shell Company

false

Entity Public Float

$ 3,005,104,706

Entity Common Stock, Shares Outstanding

78,161,596

Document Fiscal Year Focus

2023

Document Fiscal Period Focus

Entity Central Index Key

0000104918

Current Fiscal Year End Date

--12-31

ICFR Auditor Attestation Flag

true

Documents Incorporated by Reference

Documents Incorporated By Reference

      Document

      Part of Form 10-K into Which
Document is Incorporated

      Proxy Statement to be filed in connection with the annual meeting of shareholders to be held on May 1, 2024.
Prior to such filing, the Proxy Statement was filed in connection with the annual meeting of shareholders held on May 11, 2023.

      Part III, Items 10, 11,
12, 13 and 14

Auditor Name

Deloitte & Touche LLP

Auditor Location

Portland, Oregon

Auditor Firm ID

Jointly Owned Electric Facilities - Schedule of Utility Plant in Service for Colstrip And Accumulated Depreciation (Details) - Colstrip Generating Project [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Jointly Owned Utility Plant Interests [Line Items]
Utility plant in service	$ 394,398	$ 390,852
Accumulated depreciation	$ (334,338)	$ (315,223)

Commitments and Contingencies - Ownership and Operating Interest Percentage (Details)	Dec. 31, 2023	Jan. 16, 2023	Sep. 30, 2022
Loss Contingencies [Line Items]
Owners percentage interest	15.00%
Avista [Member] \| Unit 3 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	15.00%
Avista [Member] \| Unit 4 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	15.00%
Pacificorp [Member] \| Unit 3 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	10.00%
Pacificorp [Member] \| Unit 4 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	10.00%
PGE [Member] \| Unit 3 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	20.00%
PGE [Member] \| Unit 4 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	20.00%
PSE [Member] \| Unit 3 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	25.00%
PSE [Member] \| Unit 4 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	25.00%		25.00%
NorthWestern [Member] \| Unit 4 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	30.00%	15.00%
Talen [Member] \| Unit 3 [Member] \| Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest	30.00%

Jointly Owned Electric Facilities (Tables)

12 Months Ended

Dec. 31, 2023

Jointly Owned Utility Plant, Net Ownership Amount [Abstract]

Schedule of Utility Plant in Service for Colstrip And Accumulated Depreciation

The Company’s share of utility plant in service for Colstrip and accumulated depreciation (inclusive of the ARO assets and accumulated amortization) were as follows as of December 31 (dollars in thousands):


	2023			2022
Utility plant in service	$	394,398		$	390,852
Accumulated depreciation		(334,338	)		(315,223	)

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Summary Of Significant Accounting Policies [Line Items]
Unrecognized tax benefits, income tax penalties and interest expense	$ 0	$ 0	$ 0
Government grants	1,500,000	6,100,000
Goodwill carrying amount	52,426,000	52,426,000
Goodwill accumulated impairment losses	$ 0
Restricted Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Award vesting period	3 years
Total Shareholder Return Market-Based Awards and Performance Awards [Member]
Summary Of Significant Accounting Policies [Line Items]
Award vesting period	3 years
Dividend component liability, current	$ 2,200,000	$ 1,700,000
Total Shareholder Return Market-Based Awards and Performance Awards [Member] \| Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Common stock issued range, percent of the performance shares granted	0.00%
Total Shareholder Return Market-Based Awards and Performance Awards [Member] \| Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Common stock issued range, percent of the performance shares granted	200.00%

Fair Value - Additional Information (Details)	Dec. 31, 2023 Investment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of equity investments measured at fair value on recurring basic	2
Measurement Input, Quoted Price [Member] \| Secured and Unsecured Debt [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, measurement input	1.0000
Measurement Input, Quoted Price [Member] \| Minimum [Member] \| Secured and Unsecured Debt [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, measurement input	0.6273
Measurement Input, Quoted Price [Member] \| Maximum [Member] \| Secured and Unsecured Debt [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, measurement input	1.07245

Derivatives and Risk Management - Summary of Foreign Currency Exchange Derivatives (Details) $ in Thousands, $ in Thousands	Dec. 31, 2023 CAD ($) DerivativeContracts	Dec. 31, 2023 USD ($) DerivativeContracts	Dec. 31, 2022 CAD ($) DerivativeContracts	Dec. 31, 2022 USD ($) DerivativeContracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Number of contracts \| DerivativeContracts	5	5	19	19
United States of America, Dollars [Member] \| Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Notional amount		$ 81		$ 8,563
Canada, Dollars [Member] \| Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Notional amount	$ 109		$ 11,659

Balance Sheet Components - Schedule of Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$ 0	$ 66,142
Prepayments	52,752	30,201
Income taxes receivable	29,234	30,740
Derivative assets net of collateral	11,821	18,198
Other	9,977	5,886
Total	$ 103,784	$ 151,167

Derivatives and Risk Management (Tables)

12 Months Ended

Dec. 31, 2023

Derivative Instruments and Hedges, Assets [Abstract]

Schedule of Energy Commodity Derivative Volumes

The following table presents the underlying energy commodity derivative volumes as of December 31, 2023 expected to be delivered in each respective year (in thousands of MWhs and mmBTUs):


	Purchases								Sales
	Electric Derivatives				Gas Derivatives				Electric Derivatives				Gas Derivatives
Year	Physical (1) MWh		Financial (1) MWh		Physical (1) mmBTUs		Financial (1) mmBTUs		Physical (1) MWh		Financial (1) MWh		Physical (1) mmBTUs		Financial (1) mmBTUs
2024		9		—		22,747		74,596		472		510		1,723		12,038
2025		—		—		12,505		19,590		11		96		1,115		1,125
2026		—		—		5,570		3,940		—		—		—		—

As of December 31, 2023, there are no expected deliveries of energy commodity derivatives after 2026.

The following table presents the underlying energy commodity derivative volumes as of December 31, 2022 that were expected to be delivered in each respective year (in thousands of MWhs and mmBTUs):


	Purchases								Sales
	Electric Derivatives				Gas Derivatives				Electric Derivatives				Gas Derivatives
Year	Physical (1) MWh		Financial (1) MWh		Physical (1) mmBTUs		Financial (1) mmBTUs		Physical (1) MWh		Financial (1) MWh		Physical (1) mmBTUs		Financial (1) mmBTUs
2023		5		—		19,140		79,253		136		1,011		4,145		29,473
2024		—		—		533		30,658		—		—		1,370		9,668
2025		—		—		450		4,895		—		—		1,115		1,125

As of December 31, 2022, there were no expected deliveries of energy commodity derivatives after 2025.

(1)

Physical transactions represent commodity transactions in which Avista Corp. will take or make delivery of either electricity or natural gas; financial transactions represent derivative instruments with delivery of cash in the amount of

the benefit or cost but with no physical delivery of the commodity, such as futures, swap derivatives, options, or forward contracts.

Summary of Foreign Currency Exchange Derivatives

The following table summarizes the foreign currency exchange derivatives outstanding as of December 31 (dollars in thousands):


	2023		2022
Number of contracts		5		19
Notional amount (in United States dollars)	$	81	$	8,563
Notional amount (in Canadian dollars)		109		11,659

Summary of Unsettled Interest Rate Swap Derivatives

The following table summarizes the unsettled interest rate swap derivatives outstanding as of the balance sheet date indicated below (dollars in thousands):


Balance Sheet Date	Number of Contracts		Notional Amount		Mandatory Cash Settlement Date
December 31, 2023		2	$	20,000	2024
		1		10,000	2025
December 31, 2022		4	$	40,000	2023
		1		10,000	2024

Schedules of Fair Values and Locations of Derivative Instruments

The following table presents the fair values and locations of derivative instruments recorded on the Consolidated Balance Sheets as of December 31, 2023 (dollars in thousands):


	Fair Value
Derivative and Balance Sheet Location	Gross Asset		Gross Liability			Collateral Netting		Net Asset (Liability) on Balance Sheet
Foreign currency exchange derivatives
Other current assets	$	2	$	—		$	—	$	2
Interest rate swap derivatives
Other current assets		3,667		—			—		3,667
Other non-current liabilities and deferred credits		—		(182	)		—		(182	)
Energy commodity derivatives
Other current assets		8,531		(379	)		—		8,152
Other current liabilities		19,510		(79,082	)		42,355		(17,217	)
Other non-current liabilities and deferred credits		2,913		(20,633	)		—		(17,720	)
Total derivative instruments recorded on the balance sheet	$	34,623	$	(100,276	)	$	42,355	$	(23,298	)

The following table presents the fair values and locations of derivative instruments recorded on the Consolidated Balance Sheets as of December 31, 2022 (dollars in thousands):


	Fair Value
Derivative and Balance Sheet Location	Gross Asset		Gross Liability			Collateral Netting		Net Asset (Liability) on Balance Sheet
Foreign currency exchange derivatives
Other current assets	$	43	$	—		$	—	$	43
Other current liabilities		—		(3	)		—		(3	)
Interest rate swap derivatives
Other current assets		8,536		—			—		8,536
Other property and investments-net and other non-current assets		2,648		—			—		2,648
Other current liabilities		—		(52	)		—		(52	)
Energy commodity derivatives
Other current assets		32,257		(22,638	)		—		9,619
Other property and investments-net and other non-current assets		312		(16	)		—		296
Other current liabilities		107,902		(229,607	)		94,850		(26,855	)
Other non-current liabilities and deferred credits		6,049		(24,530	)		10,589		(7,892	)
Total derivative instruments recorded on the balance sheet	$	157,747	$	(276,846	)	$	105,439	$	(13,660	)

Schedule of Collateral Outstanding Related to Derivative Instruments

The following table presents collateral outstanding related to its derivative instruments as of December 31 (dollars in thousands):


	2023		2022
Energy commodity derivatives
Cash collateral posted	$	43,095	$	171,581
Letters of credit outstanding		20,000		49,425
Balance sheet offsetting (cash collateral against net derivative positions)		42,355		105,439

There were no letters of credit outstanding related to interest rate swap derivatives as of December 31, 2023 and December 31, 2022.

Certain of Avista Corp.’s derivative instruments contain provisions requiring Avista Corp. to maintain an “investment grade” credit rating from the major credit rating agencies. If Avista Corp.’s credit ratings were to fall below “investment grade,” it would be in violation of these provisions, and the counterparties to the derivative instruments could request immediate payment or demand immediate and ongoing collateralization on derivative instruments in net liability positions.

The following table presents the aggregate fair value of all derivative instruments with credit-risk-related contingent features in a liability position and the amount of additional collateral Avista Corp. could be required to post as of December 31 (dollars in thousands):


	2023
Interest rate swap derivatives
Liabilities with credit-risk-related contingent features	$	182
Additional collateral to post		182
Energy commodity derivatives
Liabilities with credit-risk-related contingent features	$	18,016
Additional collateral to post		15,125

Long-Term Debt - Schedule Of Long-Term Debt Maturities (Details) - Future Long Term Debt Maturities Including Long Term Debt To Affiliated Trusts [Member] $ in Thousands	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
2024	$ 15,000
2028	25,000
Thereafter	2,561,547
Total	$ 2,601,547

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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-Topic 470
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Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

Balance Sheet Related Disclosures [Abstract]

Accounting For Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018	Dec. 31, 2017
Components of Income Tax Expense (Benefit) [Line Items]
Federal statutory tax rate	21.00%	21.00%	21.00%	21.00%	35.00%
State Tax Credit Carryforward [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Tax credit carryforward, amount	$ 17.3
Tax credit carryforwards, net of valuation allowance	6.8
Tax credit carryforward, valuation allowance	$ (10.5)
Minimum [Member] \| State Tax Credit Carryforward [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Tax credit carryforward, expiration date	2024
Maximum [Member] \| State Tax Credit Carryforward [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Tax credit carryforward, expiration date	2037

Fair Value - Schedule of Quantitative Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) MMBTU $ / MMBTU
Fair Value, Recurring [Member] \| Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments	$ 50,254
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Fair Value, Recurring [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative Liability	$ (8,250)
Internally Derived Weighted Average Cost Of Gas [Member] \| Purchase [Member] \| Minimum [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Transaction/Delivery Volumes \| MMBTU	300,000
Derivative, Forward Price \| $ / MMBTU	1.64
Internally Derived Weighted Average Cost Of Gas [Member] \| Purchase [Member] \| Maximum [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Transaction/Delivery Volumes \| MMBTU	310,000
Derivative, Forward Price \| $ / MMBTU	3.07
Internally Derived Weighted Average Cost Of Gas [Member] \| Purchase [Member] \| Weighted Average [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative, Forward Price \| $ / MMBTU	2.4
Internally Derived Weighted Average Cost Of Gas [Member] \| Sales [Member] \| Minimum [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Transaction/Delivery Volumes \| MMBTU	75,000
Derivative, Forward Price \| $ / MMBTU	2.13
Internally Derived Weighted Average Cost Of Gas [Member] \| Sales [Member] \| Maximum [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Transaction/Delivery Volumes \| MMBTU	310,000
Derivative, Forward Price \| $ / MMBTU	8.99
Internally Derived Weighted Average Cost Of Gas [Member] \| Sales [Member] \| Weighted Average [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative, Forward Price \| $ / MMBTU	5.45
Market Approach [Member] \| Minimum [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, comparable enterprise values	$ 130,000
Equity investments, time to liquidity event	1 year 6 months
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Market Approach [Member] \| Maximum [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, comparable enterprise values	$ 388,600
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Market Approach [Member] \| Weighted Average [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, comparable enterprise values	$ 246,000
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Discounted Cash Flows [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, terminal date	2027
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Discounted Cash Flows [Member] \| Discount Rate [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	25
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Discounted Cash Flows [Member] \| Market Exit Reduction [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	50
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Discounted Cash Flows [Member] \| Revenue Market Multiples [Member] \| Minimum [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	0.45
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Discounted Cash Flows [Member] \| Revenue Market Multiples [Member] \| Maximum [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	5.69
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Discounted Cash Flows [Member] \| Revenue Market Multiples [Member] \| Weighted Average [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	1.89
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Discounted Cash Flows [Member] \| Annual Revenues [Member] \| Minimum [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, annual revenues	$ 15,000
Investment, Type [Extensible Enumeration]	Equity Funds [Member]
Discounted Cash Flows [Member] \| Annual Revenues [Member] \| Maximum [Member] \| Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, annual revenues	$ 245,000
Investment, Type [Extensible Enumeration]	Equity Funds [Member]

Balance Sheet Components - Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Accrued taxes other than income taxes	$ 31,928	$ 38,568
Employee paid time off accruals	32,072	29,279
Accrued interest	23,539	20,863
Pensions and other postretirement benefits	14,082	15,625
Derivative liabilities	17,217	26,910
Climate Commitment Act obligations	19,081	0
Deferred wholesale revenue	0	8,481
Other	54,017	49,689
Total	$ 191,936	$ 189,415

Long-Term Debt - Schedule Of Long-Term Debt Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Secured Debt	$ 2,618,700	$ 2,382,200
Secured and Unsecured Debt	2,633,700	2,397,200
Unamortized debt discount	(689)	(726)
Unamortized Debt Issuance Expense	(18,953)	(18,261)
Total	2,614,058	2,378,213
Current portion of long-term debt	(15,000)	(13,500)
Non Affiliated Trusts [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,515,358	2,281,013
First Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	$ (83,700)	(83,700)
2032 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	66,700
2034 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	17,000
Avista Utilities [Member]
Debt Instrument [Line Items]
Secured Debt	$ 2,543,700	2,307,200
Avista Utilities [Member] \| 2023 7.18% - 7.54% [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2023
Medium-Term Notes, Noncurrent	$ 0	13,500
Avista Utilities [Member] \| 2023 7.18% - 7.54% [Member] \| Minimum [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.18%
Avista Utilities [Member] \| 2023 7.18% - 7.54% [Member] \| Maximum [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.54%
Avista Utilities [Member] \| 2028 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2028
Debt Instrument, Interest Rate, Stated Percentage	6.37%
Medium-Term Notes, Noncurrent	$ 25,000	25,000
Avista Utilities [Member] \| 2032 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2032
Pollution Control Bonds	$ 66,700	66,700
Avista Utilities [Member] \| 2034 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2034
Pollution Control Bonds	$ 17,000	17,000
Avista Utilities [Member] \| 2035 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2035
Debt Instrument, Interest Rate, Stated Percentage	6.25%
Secured Debt	$ 150,000	150,000
Avista Utilities [Member] \| 2037 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2037
Debt Instrument, Interest Rate, Stated Percentage	5.70%
Secured Debt	$ 150,000	150,000
Avista Utilities [Member] \| 2040 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2040
Debt Instrument, Interest Rate, Stated Percentage	5.55%
Secured Debt	$ 35,000	35,000
Avista Utilities [Member] \| 2041 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2041
Debt Instrument, Interest Rate, Stated Percentage	4.45%
Secured Debt	$ 85,000	85,000
Avista Utilities [Member] \| 2044 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2044
Debt Instrument, Interest Rate, Stated Percentage	4.11%
Secured Debt	$ 60,000	60,000
Avista Utilities [Member] \| 2045 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2045
Debt Instrument, Interest Rate, Stated Percentage	4.37%
Secured Debt	$ 100,000	100,000
Avista Utilities [Member] \| 2047 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2047
Debt Instrument, Interest Rate, Stated Percentage	4.23%
Secured Debt	$ 80,000	80,000
Avista Utilities [Member] \| 2047 3.91% [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2047
Debt Instrument, Interest Rate, Stated Percentage	3.91%
Secured Debt	$ 90,000	90,000
Avista Utilities [Member] \| 2048 4.35% [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2048
Debt Instrument, Interest Rate, Stated Percentage	4.35%
Secured Debt	$ 375,000	375,000
Avista Utilities [Member] \| 2049 3.43% [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2049
Debt Instrument, Interest Rate, Stated Percentage	3.43%
Secured Debt	$ 180,000	180,000
Avista Utilities [Member] \| 2050 3.07% [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2050
Debt Instrument, Interest Rate, Stated Percentage	3.07%
Secured Debt	$ 165,000	165,000
Avista Utilities [Member] \| 2051 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2051
Debt Instrument, Interest Rate, Stated Percentage	3.54%
Secured Debt	$ 175,000	175,000
Avista Utilities [Member] \| 2.90% Due in 2051 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2051
Debt Instrument, Interest Rate, Stated Percentage	2.90%
Secured Debt	$ 140,000	140,000
Avista Utilities [Member] \| 2052 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2052
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Secured Debt	$ 400,000	400,000
Avista Utilities [Member] \| 2053 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2053
Debt Instrument, Interest Rate, Stated Percentage	5.66%
Secured Debt	$ 250,000
Alaska Electric Light & Power [Member] \| 2044 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2044
Debt Instrument, Interest Rate, Stated Percentage	4.54%
Secured Debt	$ 75,000	75,000
Alaska Energy Resources Company [Member] \| 2024 [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Maturity Year	2024
Debt Instrument, Interest Rate, Stated Percentage	3.44%
Unsecured Debt	$ 15,000	$ 15,000

Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Balance Sheet Components

NOTE 3. BALANCE SHEET COMPONENTS

Inventory

Inventories of materials and supplies, emissions allowances, stored natural gas and fuel stock are recorded at average cost and consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Materials and supplies	$	81,651	$	75,766
Emission allowances		56,097		—
Stored natural gas		16,272		26,788
Fuel stock		5,964		5,120
Total	$	159,984	$	107,674

Other Current Assets

Other current assets consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$	—	$	66,142
Prepayments		52,752		30,201
Income taxes receivable		29,234		30,740
Derivative assets net of collateral		11,821		18,198
Other		9,977		5,886
Total	$	103,784	$	151,167

Other Property and Investments-Net and Other Non-Current Assets

Other property and investments-net and other non-current assets consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Equity investments	$	153,350	$	147,809
Operating lease ROU assets		67,585		68,238
Finance lease ROU assets		36,414		40,056
Non-utility property		33,813		25,401
Notes receivable		15,287		17,954
Long-term prepaid license fees		19,448		17,936
Pension assets		32,997		13,382
Investment in affiliated trust		11,547		11,547
Deferred compensation assets		7,794		7,541
Other		15,750		15,221
Total	$	393,985	$	365,085

Other Current Liabilities

Other current liabilities consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Accrued taxes other than income taxes	$	31,928	$	38,568
Employee paid time off accruals		32,072		29,279
Accrued interest		23,539		20,863
Pensions and other postretirement benefits		14,082		15,625
Derivative liabilities		17,217		26,910
Climate Commitment Act obligations		19,081		—
Deferred wholesale revenue		—		8,481
Other		54,017		49,689
Total	$	191,936	$	189,415

Other Non-Current Liabilities and Deferred Credits

Other non-current liabilities and deferred credits consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Operating lease liabilities	$	63,559	$	64,284
Finance lease liabilities		39,095		42,495
Deferred investment tax credits		28,233		28,784
Climate Commitment Act obligations		26,026		—
Asset retirement obligations		18,058		15,783
Derivative liabilities		17,902		7,892
Other		17,357		16,617
Total	$	210,230	$	175,855

Leases - Additional Information (Details)	12 Months Ended
Leases - Additional Information (Details)	Dec. 31, 2023
Lessee, Lease, Description [Line Items]
Operating lease, existence of option to extend	true
Minimum [Member]
Lessee, Lease, Description [Line Items]
Operating lease, remaining terms of contract	1 year
Operating lease, options to extend lease term	5 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Operating lease, remaining terms of contract	70 years
Operating lease, options to extend lease term	50 years
Snettisham Hydroelectric Project [Member]
Lessee, Lease, Description [Line Items]
Finance lease expiration year	2034
State of Montana [Member] \| Hydroelectric Facilities in the Clark Fork River Basin [Member]
Lessee, Lease, Description [Line Items]
Operating lease expiration year	2046

Variable Interest Entities

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Variable Interest Entities

NOTE 6. VARIABLE INTEREST ENTITIES

Under GAAP, a limited partnership or similar legal entity that is the functional equivalent of a limited partnership is considered a VIE regardless of whether it otherwise qualifies as a voting interest entity unless a simple majority or lower threshold of the “unrelated” limited partners (i.e., parties other than the general partner, entities under common control with the general partner, and other parties acting on behalf of the general partner) have substantive kick-out rights (including liquidation rights) or participating rights.

The Company has investments in limited partnerships (or the functional equivalent) where Avista Corp. is a limited partner investor in an investment fund where the general partner makes all of the investment and operating decisions with regards to the partnership and fund. To remove the general partner from any of the funds, approval from greater than a simple majority of the limited partners is required. As such, the limited partners do not have substantive kick-out rights and these investments are considered VIEs. Consolidation of these VIEs by Avista Corp. is not required because the Company does not have majority ownership in any of the funds, it does not have the power to direct activities of the funds, and it does not have the power to appoint executive leadership, including the board of directors.

Avista Corp. participates in profits and losses of the investment funds based on its ownership percentage and its losses are capped at its total initial investment in the funds. Equity investments in VIEs are accounted for under the equity method (see Note 7). As of December 31, 2023, Avista Corp. has invested $73.3 million in these investment funds, with an additional commitment of $17.7 million remaining to be invested. The Company is not allowed to withdraw capital contributions from an investment fund until after that fund expiration date and all liabilities of that fund are settled. The expiration dates range from 2025 to 2036, with some investments having no termination date (as they are perpetual). As of December 31, 2023, the Company has a total carrying amount of $88.1 million in these VIEs, including $78.5 million of equity investments and $9.6 million of notes receivable.

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Accounting For Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Accounting for Income Taxes

NOTE 13. ACCOUNTING FOR INCOME TAXES

Income Tax Expense

Income tax expense consisted of the following for the years ended December 31 (dollars in thousands):


	2023			2022			2021
Current income tax expense	$	3,207		$	1,040		$	807
Deferred income tax expense (benefit)		(36,837	)		(18,231	)		11,224
Total income tax expense (benefit)	$	(33,630	)	$	(17,191	)	$	12,031

A reconciliation of federal income taxes derived from the statutory federal tax rate of 21 percent applied to income before income taxes is as follows for the years ended December 31 (dollars in thousands):


	2023					2022					2021
Federal income taxes at statutory rates	$	28,886		21.0	%	$	28,977		21.0	%	$	33,467		21.0	%
Increase (decrease) in tax resulting from:
Tax effect of regulatory treatment of utility plant differences (1)		(12,270	)	(8.9	)		(12,366	)	(9.0	)		(13,820	)	(8.7	)
State income tax expense		2,077		1.5			1,676		1.2			1,385		0.8
Flow through related to deduction of meters and mixed service costs (2)		(47,983	)	(34.9	)		(34,454	)	(25.0	)		(8,678	)	(5.4	)
Tax credits		(2,334	)	(1.7	)		(258	)	(0.2	)		(75	)	—
Other		(2,006	)	(1.4	)		(766	)	(0.5	)		(248	)	(0.2	)
Total income tax expense (benefit)	$	(33,630	)	(24.4	)%	$	(17,191	)	(12.5	)%	$	12,031		7.5	%

(1)

Prior to 2022, for the depreciation-related temporary differences under the normalization tax accounting method, the Company utilized the average rate assumption method to compute the amounts returned to customers. Beginning in 2022, the Company changed to the alternative method, to comply with the revenue procedure and private letter rulings.

(2)

The Company's general rate cases included approval of base rate increases, offset by tax customer credits. As the tax customer credits are returned to customers, this results in a decrease to income tax expense due to flowing through the benefits related to meters and mixed service costs.

Deferred Income Taxes

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and tax credit carryforwards. The total net deferred income tax liability consisted of the following as of December 31 (dollars in thousands):


	2023			2022
Deferred income tax assets:
Regulatory liabilities	$	192,099		$	197,998
Tax credits and net operating loss carryforwards		76,969			74,782
Provisions for pensions		19,100			20,132
Other		47,839			54,903
Total gross deferred income tax assets		336,007			347,815
Valuation allowances for deferred tax assets		(10,461	)		(3,874	)
Total deferred income tax assets after valuation allowances		325,546			343,941
Deferred income tax liabilities:
Utility property, plant, and equipment		746,876			712,470
Regulatory assets		268,833			281,483
Other		28,155			24,983
Total deferred income tax liabilities		1,043,864			1,018,936
Net long-term deferred income tax liability	$	718,318		$	674,995

The realization of deferred income tax assets is dependent upon the ability to generate taxable income in future periods. The Company evaluated available evidence supporting the realization of its deferred income tax assets and determined it is more likely than not that deferred income tax assets will be realized.

As of December 31, 2023, the Company had $17.3 million of state tax credit carryforwards. Of the total amount, the Company believes that it is more likely than not that it will only be able to utilize $6.8 million of the state tax credits. As such, the Company has recorded a valuation allowance of $10.5 million against the state tax credit carryforwards and reflected the net amount of $6.8 million as an asset as of December 31, 2023. State tax credits expire from 2024 to 2037.

Status of Internal Revenue Service (IRS) and State Examinations

The Company and its eligible subsidiaries file consolidated federal income tax returns. All tax years after 2018 are open for an IRS tax examination. The IRS is reviewing tax year 2019.

The Company files state income tax returns in certain jurisdictions, including Idaho, Oregon, Montana and Alaska. Subsidiaries are charged or credited with the tax effects of their operations on a stand-alone basis.

All tax years after 2019 are open for examination in Idaho, Oregon, Montana and Alaska.

The Company believes open tax years for federal or state income taxes will not result in adjustments that would be significant to the consolidated financial statements.

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Derivatives and Risk Management - Schedules of Fair Values and Locations of Derivative Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Gross Asset	$ 34,623	$ 157,747
Gross Liability	(100,276)	(276,846)
Collateral Netting	42,355	105,439
Net Asset (Liability) on Balance Sheet	(23,298)	(13,660)
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netting	42,355	105,439
Other Current Assets [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	2	43
Net Asset (Liability) on Balance Sheet	2	43
Other Current Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	3,667	8,536
Net Asset (Liability) on Balance Sheet	3,667	8,536
Other Current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	8,531	32,257
Gross Liability	(379)	(22,638)
Net Asset (Liability) on Balance Sheet	8,152	9,619
Other Property and Investments-Net and Other Non-current Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		2,648
Net Asset (Liability) on Balance Sheet		2,648
Other Property and Investments-Net and Other Non-current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		312
Gross Liability		(16)
Net Asset (Liability) on Balance Sheet		296
Other Current Liabilities [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Liability		(3)
Net Asset (Liability) on Balance Sheet		(3)
Other Current Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Liability		(52)
Net Asset (Liability) on Balance Sheet		(52)
Other Current Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	19,510	107,902
Gross Liability	(79,082)	(229,607)
Collateral Netting	42,355	94,850
Net Asset (Liability) on Balance Sheet	(17,217)	(26,855)
Other Noncurrent Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Liability	(182)
Net Asset (Liability) on Balance Sheet	(182)
Other Noncurrent Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	2,913	6,049
Gross Liability	(20,633)	(24,530)
Collateral Netting		10,589
Net Asset (Liability) on Balance Sheet	$ (17,720)	$ (7,892)

Information by Business Segments - Schedule of Business Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 1,751,554	$ 1,710,207	$ 1,438,936
Resource costs	702,372	735,862	497,123
Other operating expenses	416,368	416,768	372,052
Depreciation and amortization	265,409	253,142	232,176
Income (loss) from operations	257,690	190,242	228,232
Interest expense	143,299	118,692	106,152
Income tax expense (benefit)	(33,630)	(17,191)	12,031
Net income (loss)	171,180	155,176	147,334
Capital expenditures	498,637	452,829	441,209
Total Assets	7,702,477	7,417,350	6,853,583
Operating Segments [Member] \| Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,750,996	1,709,519	1,438,365
Resource costs	702,372	735,862	497,123
Other operating expenses	413,608	405,165	366,125
Depreciation and amortization	265,329	253,017	231,915
Income (loss) from operations	259,972	201,282	233,849
Interest expense	142,776	118,173	105,725
Income tax expense (benefit)	(32,038)	(25,031)	8,792
Net income (loss)	175,953	125,446	132,782
Capital expenditures	498,637	451,995	439,939
Total Assets	7,532,387	7,240,486	6,723,666
Operating Segments [Member] \| Avista Utilities [Member] \| Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,702,857	1,663,815	1,392,999
Resource costs	698,546	732,298	493,289
Other operating expenses	398,523	390,597	352,241
Depreciation and amortization	254,401	242,198	221,552
Income (loss) from operations	242,678	185,582	217,663
Interest expense	136,924	112,213	99,629
Income tax expense (benefit)	(35,353)	(27,368)	6,029
Net income (loss)	167,016	117,901	125,558
Capital expenditures	484,716	443,373	435,887
Total Assets	7,262,704	6,976,164	6,458,244
Operating Segments [Member] \| Alaska Electric Light & Power [Member] \| Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	48,139	45,704	45,366
Resource costs	3,826	3,564	3,834
Other operating expenses	15,085	14,568	13,884
Depreciation and amortization	10,928	10,819	10,363
Income (loss) from operations	17,294	15,700	16,186
Interest expense	5,852	5,960	6,096
Income tax expense (benefit)	3,315	2,337	2,763
Net income (loss)	8,937	7,545	7,224
Capital expenditures	13,921	8,622	4,052
Total Assets	269,683	264,322	265,422
Other [Member] \| Non-Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	558	688	571
Resource costs	0	0	0
Other operating expenses	2,760	11,603	5,927
Depreciation and amortization	80	125	261
Income (loss) from operations	(2,282)	(11,040)	(5,617)
Interest expense	1,881	791	522
Income tax expense (benefit)	(1,592)	7,840	3,239
Net income (loss)	(4,773)	29,730	14,552
Capital expenditures	0	834	1,270
Total Assets	191,665	187,027	132,158
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0
Resource costs	0	0	0
Other operating expenses	0	0	0
Depreciation and amortization	0	0	0
Income (loss) from operations	0	0	0
Interest expense	(1,358)	(272)	(95)
Income tax expense (benefit)	0	0	0
Net income (loss)	0	0	0
Capital expenditures	0	0	0
Total Assets	$ (21,575)	$ (10,163)	$ (2,241)

Credit Agreements - Additional Information (Details) - Avista Utilities [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Credit agreement amount borrowed		$ 150,000
Letters of credit outstanding	$ 4,700		$ 35,563
Line of credit facility, covenant terms, maximum debt to equity ratio	65.00%

Long-Term Debt - Additional Information (Details) - First Mortgage [Member] $ in Millions	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Avista Utilities [Member]
Debt Instrument [Line Items]
Amount of First Mortgage Bonds that Could be Issued, Percent	66.66%
Amount of First Mortgage Bonds that Could be Issued	$ 1,200.0
Alaska Electric Light & Power [Member]
Debt Instrument [Line Items]
Amount of First Mortgage Bonds that Could be Issued, Percent	66.66%
Amount of First Mortgage Bonds that Could be Issued	$ 51.4

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Schedule of Regulatory Assets and Liabilities

Energy Purchase Contracts (PUD Contracts Expenses) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
P U D Contracts Expenses [Abstract]
Long-term contract for purchase of electric power, amount of long-term debt or lease obligation outstanding	$ 275.1

Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2023

Regulated Operations [Abstract]

The following table presents the Company’s regulatory assets and liabilities as of December 31, 2023 (dollars in thousands):


				Receiving Regulatory Treatment						2023				2022
	Remaining Amortization Period			(1) Earning A Return		Not Earning A Return		(2) Expected Recovery or Refund		Current		Non- current		Current		Non- current
Regulatory Assets:
Deferred income tax	(3) (16)			$	—	$	244,303	$	—	$	—	$	244,303	$	—	$	240,325
Pensions and other postretirement benefit plans		(4	)		—		117,658		—		—		117,658		—		135,337
Climate Commitment Act		(14	)		46,022		—		—		—		46,022		—		—
Energy commodity derivatives		(5	)		—		69,139		—		51,419		17,720		112,090		18,185
Unamortized debt repurchase costs		(6	)		5,701		—		—		—		5,701		—		6,177
Settlement with Coeur d’Alene Tribe	2059				36,692		—		—		—		36,692		—		37,809
Demand side management programs		(3	)		—		10,033		—		—		10,033		—		3,683
Decoupling surcharge	2025				10,107		—		—		4,638		5,469		6,250		5,449
Utility plant abandoned		(7	)		34,852		3,422		—		—		38,274		—		24,389
Interest rate swaps		(8	)		178,898		—		591		—		179,489		—		185,919
Deferred power costs		(3	)		49,844		—		—		29,190		20,654		23,356		24,043
Deferred natural gas costs		(3	)		60,667		—		—		60,667		—		52,091		—
AFUDC above FERC allowed rate		(11	)		49,985		—		—		—		49,985		—		51,649
COVID-19 deferrals		(12	)		—		—		12,142		—		12,142		—		9,793
Advanced meter infrastructure		(13	)		29,345		—		—		—		29,345		—		32,381
Other regulatory assets		(3	)		41,072		35,793		4,229		413		80,681		—		58,189
Total regulatory assets				$	543,185	$	480,348	$	16,962	$	146,327	$	894,168	$	193,787	$	833,328
Regulatory Liabilities:
Deferred natural gas costs		(3	)	$	9,296	$	—	$	—	$	9,296	$	—	$	—	$	—
Deferred power costs		(3	)	$	4,000	$	—	$	—	$	—	$	4,000	$	—	$	—
Utility plant retirement costs		(9	)		417,027		—		—		—		417,027		—		376,817
Excess deferred income taxes		(10	)		307,539		—		—		14,510		293,029		15,310		314,096
Other income tax related liabilities	(3) (15)				—		81,711		—		25,129		56,582		57,957		76,638
Climate Commitment Act		(14	)		37,231		—		—		—		37,231		—		—
Interest rate swaps		(8	)		12,216		—		11,536		—		23,752		—		24,204
Decoupling rebate	2025				25,024		—		—		18,680		6,344		9,469		20,476
COVID-19 deferrals		(12	)		—		8		10,164		—		10,172		—		11,874
Other regulatory liabilities		(3	)		4,298		12,623		—		8,392		8,529		12,929		16,732
Total regulatory liabilities				$	816,631	$	94,342	$	21,700	$	76,007	$	856,666	$	95,665	$	840,837

(1)

Earning a return includes either interest on the regulatory asset/liability or a return on the investment as a component of rate base at the allowed rate of return.

(2)

Expected recovery is pending regulatory treatment including regulatory assets and liabilities with prior regulatory precedence.

(3)

Remaining amortization period varies depending on timing of underlying transactions.

(4)

As the Company has historically recovered and currently recovers its pension and other postretirement benefit costs related to its regulated operations in retail rates, the Company records a regulatory asset for that portion of its pension and other postretirement benefit funding deficiency.

(5)

The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and losses result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho and periodic general rates cases. The resulting regulatory assets associated with energy commodity derivative instruments have been concluded to be probable of recovery through future rates.

(6)

(7)

The WUTC approved recovery of AMI project costs through the 2020 general rate case settlements, including amortization of retired meters replaced through the project through 2033. The IPUC approved deferral accounting treatment for the Idaho AMI project, which will be included in a future rate case. In addition, the IPUC approved the depreciation of Colstrip through 2027, and as such the remaining depreciation after our exit of Colstrip in 2025 is included in this balance. There are additional smaller projects included in the balance the Company expects to fully recover, which have not yet been through the regulatory process.

(8)

For interest rate swap derivatives, Avista Corp. records all mark-to-market gains and losses in each accounting period as assets and liabilities, as well as offsetting regulatory assets and liabilities, such that there is no income statement impact. The interest rate swap derivatives are risk management tools similar to energy commodity derivatives. Upon settlement of interest rate swap derivatives, the regulatory asset or liability is amortized as a component of interest expense over the term of the associated debt. The Company records an offset of interest rate swap derivative assets and liabilities with regulatory assets and liabilities, based on the prior practice of the commissions to provide recovery through the ratemaking process. Settled interest rate swap derivatives which have been through a general rate case proceeding are classified as earning a return in the table above, whereas all unsettled interest rate swap derivatives and settled interest rate swap derivatives which have not been included in a general rate case are classified as expected recovery.

(9)

This amount is dependent upon the cost of removal of underlying utility plant assets and the life of utility plant.

(10)

This balance represents amounts due back to customers and resulted from the Tax Cuts and Jobs Act signed into law in December 2017, which changed the federal income tax rate from 35 percent to 21 percent. The Company revalued all deferred income taxes as of December 31, 2017. The Company expects the amounts for utility plant items for Avista Utilities to be returned to customers over a period of approximately 33 years. The Company expects the AEL&P amounts to be returned to customers over a period of approximately 22 years. Prior to 2022, for depreciation-related temporary differences under the normalized tax accounting method, the Company utilized the average rate assumption method to compute the amounts returned to customers. Beginning in 2022, the Company changed to the alternative method, to comply with revenue procedures and private letter rulings.

(11)

This amount is being amortized based on the underlying utility plant assets and the life of utility plant.

(12)

The WUTC, IPUC and OPUC issued accounting orders allowing the Company to defer certain costs, net of benefits, related to the COVID-19 pandemic. The Company has recorded all benefits on a gross basis as a regulatory liability to customers and all additional allowed costs are a regulatory asset. The ratemaking treatment will be determined in future general rate cases in each jurisdiction.

(13)

This amount represents the deferral of the depreciation expense of the Company’s AMI project in Washington state. Recovery of these amounts was approved by WUTC in the 2021 general rate case order, and the asset will be amortized through 2033.

(14)

Regulatory assets related to the Climate Commitment Act represent costs incurred to comply with the program. Regulatory liabilities related to the Climate Commitment Act represent proceeds from the required sale of allowances, which will be returned to customers. The Company will submit filings periodically to receive approval to include these items in customer rates.

(15)

The majority of this amount represents the remaining tax customer credits being returned to customers and the tax gross-up on tax customer credits and investment tax credits, which have a corresponding deferred tax asset within Note 13.

(16)

The majority of this balance represents flow-through income tax accounting differences and the related tax gross-up which have a corresponding deferred tax liability within Note 13.

Summary of Energy Recovery Mechanism

The following is a summary of the ERM:


Annual Power Supply Cost Variability	Deferred for Future Surcharge or Rebate to Customers	Expense or Benefit to the Company
within +/- $0 to $4 million (deadband)	0%	100%
higher by $4 million to $10 million	50%	50%
lower by $4 million to $10 million	75%	25%
higher or lower by over $10 million	90%	10%

Schedule of Decoupling and Earnings Sharing Mechanisms

As of December 31, 2023 and December 31, 2022, the Company had the following cumulative balances outstanding related to decoupling and earnings sharing mechanisms in its various jurisdictions (dollars in thousands):


	December 31,			December 31,
	2023			2022
Washington
Decoupling rebate	$	(3,232	)	$	(13,210	)
Idaho
Decoupling rebate	$	(7,961	)	$	(7,889	)
Provision for earnings sharing rebate		(572	)		(686	)
Oregon
Decoupling (rebate) surcharge	$	(3,724	)	$	2,853

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Components of Lease Expense

The components of lease expense were as follows for the year ended December 31 (dollars in thousands):


	2023		2022		2021
Operating lease cost:
Fixed lease cost (Other operating expenses)	$	5,096	$	4,986	$	4,970
Variable lease cost (Other operating expenses and Resource costs)		24,628		1,567		1,180
Total operating lease cost	$	29,724	$	6,553	$	6,150

Finance lease cost:
Amortization of ROU asset (Depreciation and amortization)	$	3,641	$	3,641	$	3,641
Interest on lease liabilities (Interest expense)		2,221		2,375		2,522
Total finance lease cost	$	5,862	$	6,016	$	6,163

Summary of Supplemental Cash Flow Information related to Leases

Supplemental cash flow information related to leases was as follows for the year ended December 31 (dollars in thousands):


	2023		2022		2021
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash outflows:
Operating lease payments	$	4,960	$	4,828	$	4,805
Interest on finance lease		2,221		2,375		2,522
Total operating cash outflows	$	7,181	$	7,203	$	7,327

Finance cash outflows:
Principal payments on finance lease	$	3,235	$	3,085	$	2,935

Summary of Supplemental Balance Sheet Information Related to Leases

Supplemental balance sheet information related to leases was as follows for December 31 (dollars in thousands):


	December 31,			December 31,
	2023			2022
Operating Leases
Operating lease ROU assets (Other property and investments-net and other non-current assets)	$	67,585		$	68,238

Other current liabilities	$	4,490		$	4,349
Other non-current liabilities and deferred credits		63,559			64,284
Total operating lease liabilities	$	68,049		$	68,633

Finance Leases
Finance lease ROU assets (Other property and investments-net and other non-current assets)	$	36,414		$	40,056

Other current liabilities	$	3,400		$	3,235
Other non-current liabilities and deferred credits		39,095			42,495
Total finance lease liabilities	$	42,495		$	45,730

Weighted Average Remaining Lease Term
Operating leases	22.28 years			23.28 years
Finance leases	4.53 years			5.42 years

Weighted Average Discount Rate
Operating leases		4.29	%		4.28	%
Finance leases		3.77	%		4.07	%

Summary of Maturities of Lease Liabilities

Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2023 (dollars in thousands):


	Operating Leases			Finance Leases
2024	$	4,988		$	5,459
2025		4,984			5,454
2026		4,981			5,456
2027		5,007			5,458
2028		4,992			5,456
Thereafter		83,532			27,292
Total lease payments	$	108,484		$	54,575
Less: imputed interest		(40,435	)		(12,080	)
Total	$	68,049		$	42,495

Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2022 (dollars in thousands):


	Operating Leases			Finance Leases
2023	$	4,850		$	5,456
2024		4,877			5,459
2025		4,884			5,454
2026		4,869			5,456
2027		4,880			5,458
Thereafter		86,991			32,748
Total lease payments	$	111,351		$	60,031
Less: imputed interest		(42,718	)		(14,301	)
Total	$	68,633		$	45,730

Summary of Maturities of Lease Liabilities

Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2023 (dollars in thousands):


	Operating Leases			Finance Leases
2024	$	4,988		$	5,459
2025		4,984			5,454
2026		4,981			5,456
2027		5,007			5,458
2028		4,992			5,456
Thereafter		83,532			27,292
Total lease payments	$	108,484		$	54,575
Less: imputed interest		(40,435	)		(12,080	)
Total	$	68,049		$	42,495

Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2022 (dollars in thousands):


	Operating Leases			Finance Leases
2023	$	4,850		$	5,456
2024		4,877			5,459
2025		4,884			5,454
2026		4,869			5,456
2027		4,880			5,458
Thereafter		86,991			32,748
Total lease payments	$	111,351		$	60,031
Less: imputed interest		(42,718	)		(14,301	)
Total	$	68,633		$	45,730

Summary of Significant Accounting Policies - Summary of Appropriated Retained Earnings Amount Included in Retained Earnings (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Appropriated Retained Earnings [Abstract]
Appropriated retained earnings	$ 59,118	$ 57,231

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss, Net of Tax (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Loss [Abstract]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans net unamortized (gain) loss, tax	$ 95	$ 547

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current Assets:
Cash and cash equivalents	$ 35,003	$ 13,428
Accounts and notes receivable, net	216,744	255,746
Inventory	159,984	107,674
Regulatory assets	146,327	193,787
Other current assets	103,784	151,167
Total current assets	661,842	721,802
Net utility property	5,700,056	5,444,709
Goodwill	52,426	52,426
Non-current regulatory assets	894,168	833,328
Other property and investments-net and other non-current assets	393,985	365,085
Total assets	7,702,477	7,417,350
Current Liabilities:
Accounts payable	143,262	202,954
Current portion of long-term debt	15,000	13,500
Short-term borrowings	349,000	463,000
Regulatory liabilities	76,007	95,665
Other current liabilities	191,936	189,415
Total current liabilities	775,205	964,534
Pensions and other postretirement benefits	89,830	93,901
Deferred income taxes	718,318	674,995
Non-current regulatory liabilities	856,666	840,837
Other non-current liabilities and deferred credits	210,230	175,855
Total liabilities	5,217,154	5,082,682
Commitments and Contingencies (See Notes to Consolidated Financial Statements)
Equity:
Common stock, no par value; 200,000,000 shares authorized; 78,073,587 and 74,945,948 shares issued and outstanding, respectively	1,644,327	1,525,185
Accumulated other comprehensive loss	(357)	(2,058)
Retained earnings	841,353	811,541
Total equity	2,485,323	2,334,668
Total liabilities and equity	7,702,477	7,417,350
Non Affiliated Trusts [Member]
Current Liabilities:
Long-term debt	2,515,358	2,281,013
Affiliated Trusts [Member]
Current Liabilities:
Long-term debt	$ 51,547	$ 51,547

Pension Plans and Other Postretirement Benefit Plans - Additional Information (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Payment for pension benefits

$ 10,000

$ 42,000

Percentage of service related net periodic benefit costs capitalized to utility property

$ 11,800

40.00%

Percentage of service related net periodic benefit costs recorded to operating expenses

60.00%

Partial Settlement of Plan [Member]

Regulatory asset amortization period

12 years

Deferred Compensation, Excluding Share-based Payments and Retirement Benefits [Member] | Executive Officer [Member]

Deferred compensation, earlier of retirement, termination, disability or death, percent

75.00%

Deferred compensation incentive payments, percent

100.00%

Equity Securities

55.00%

Debt Securities

40.00%

Real Estate [Member]

Pension Plans, Defined Benefit [Member]

5.00%

Expected contributions to pension plan

$ 10,000

Fair value of plan assets

^[1]

$ 11,828

589,983

540,703

750,963

Expected contributions to pension plan

7,100

Fair value of plan assets

$ 58,126

$ 49,472

$ 59,544

Other Postretirement Benefits [Member] | Equity Securities

Other Postretirement Benefits [Member] | Debt Securities

60.00%

Other Postretirement Benefits [Member] | Balanced Mutual Funds [Member]

40.00%

Fair value of plan assets

$ 58,100

$ 49,500

[1]	The settlement loss was deferred as a regulatory asset and is being amortized over 12 years in accordance with regulatory accounting orders.

Long-Term Debt - Schedule Of Long-Term Debt Instruments (Parenthetical) (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2023 USD ($) Contract	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt		$ 250,000	$ 399,856	$ 140,000
Repayments of short-term debt		$ 150,000
First Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		8.00%
2032 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds		$ 66,700
2034 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds		$ 17,000
5.66% Due in 2053 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt	$ 250,000
Debt Instrument, Interest Rate, Stated Percentage	5.66%
Debt instrument maturity year	2053
5.66% Due in 2053 [Member] \| First Mortgage [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Number of interest rate swaps settled \| Contract	4
Notional Amount	$ 40,000
Net payments from settlement of derivatives	$ 7,500

Accounting For Income Taxes - Schedule of Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Current income tax expense	$ 3,207	$ 1,040	$ 807
Deferred income tax expense (benefit)	(36,837)	(18,231)	11,224
Total income tax expense (benefit)	$ (33,630)	$ (17,191)	$ 12,031

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Commitments and Contingencies Disclosure [Abstract]

Information by Business Segments - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 ReportableSegments
Segment Reporting [Abstract]
Number of reportable segments	1

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies

NOTE 22. COMMITMENTS AND CONTINGENCIES

In the course of its business, the Company becomes involved in various claims, controversies, disputes and other contingent matters, including the items described in this Note. Some of these claims, controversies, disputes and other contingent matters

involve litigation or other contested proceedings. For all such matters, the Company will vigorously protect and defend its interests and pursue its rights. However, no assurance can be given as to the ultimate outcome of any matter because litigation and other contested proceedings are subject to numerous uncertainties. For matters affecting Avista Utilities’ or AEL&P's operations, the Company intends to seek, to the extent appropriate, recovery of incurred costs through the ratemaking process.

Collective Bargaining Agreements

The Company's collective bargaining agreement with the IBEW represents 36 percent of all Avista Utilities' employees. The Company's largest represented group, representing approximately 90 percent of Avista Utilities' bargaining unit employees in Washington and Idaho, are covered under a four year agreement which expires in March 2025.

The current agreement includes a clause to negotiate wages in effect for the last year of the agreement. The Company is in the process of negotiating these wages. There is a risk that if an agreement on wages is not reached, the employees subject to the agreement could strike. Given the number of employees that are covered by the collective bargaining agreement, a strike could result in disruptions to the Company's operations. However, the Company believes the possibility of this occurring is remote.

Boyds Fire (State of Washington Department of Natural Resources v. Avista)

In August 2019, the Company was served with a complaint, captioned “State of Washington Department of Natural Resources v. Avista Corporation,” seeking recovery of up to $4.4 million for fire suppression and investigation costs and related expenses incurred in connection with a wildfire that occurred in Ferry County, Washington, in August 2018. Specifically, the complaint alleges the fire, which became known as the “Boyds Fire,” was caused by a dead ponderosa pine tree falling into an overhead distribution line, and that Avista Corp., along with its independent vegetation management contractors Asplundh Tree Company and CN Utility Consulting, were negligent in failing to identify and remove the tree before it came into contact with the line. Avista Corp. disputes that it was negligent in failing to identify and remove the tree in question. Additional lawsuits were subsequently filed by private landowners seeking property damages, and holders of insurance subrogation claims seeking recovery of insurance proceeds paid.

The lawsuits were filed in the Superior Court of Ferry County, Washington. The Company continues to vigorously defend itself in the litigation. However, at this time the Company is unable to predict the likelihood of an adverse outcome or estimate a range of potential loss in the event of such an outcome.

Road 11 Fire

In April 2022, Avista Corp. received a notice of claim from property owners seeking damages of $5 million in connection with a fire that occurred in Douglas County, Washington, in July 2020. In June 2022, those claimants filed suit in the Superior Court of Douglas County, Washington, seeking unspecified damages. The fire, which was designated as the “Road 11 Fire,” occurred in the vicinity of an Avista Corp. 115kv line, resulting in damage to three overhead transmission structures. The fire occurred during a high wind event and grew to 10,000 acres before being contained. The Company disputes that it is liable for the fire and will vigorously defend itself in the pending legal proceeding; however, at this time the Company is unable to predict the likelihood of an adverse outcome or estimate a range of potential loss in the event of such an outcome.

Labor Day 2020 Windstorm

General

In September 2020, a severe windstorm occurred in eastern Washington and northern Idaho. The extreme weather event resulted in customer outages and multiple wildfires in the region.

The Company has become aware of instances where, during the storm, otherwise healthy trees and limbs, located in areas outside its maintenance right-of-way, broke under the extraordinary wind conditions and caused damage to its energy delivery system at or near what is believed to be the potential area of origin of a wildfire. However, the Company's investigations found no evidence of negligence with respect to any of those fires. Consistent with that conclusion, the statute of limitations with respect to the claims arising out of the Labor Day 2020 Windstorm has now passed and, except with respect to the Babb Road Fire discussed below, no legal action has been commenced.

Babb Road Fire

In May 2021 the Company learned the Washington Department of Natural Resources (DNR) had completed its investigation and issued a report on the Babb Road Fire. The Babb Road fire covered approximately 15,000 acres and destroyed approximately 220 structures. There are no reports of personal injury or death resulting from the fire.

The DNR report concluded, among other things, that

•

the fire was ignited when a branch of a multi-dominant Ponderosa Pine tree was broken off by the wind and fell on an Avista Corp. distribution line;

•

the tree was located approximately 30 feet from the center of Avista Corp.’s distribution line and approximately 20 feet beyond Avista Corp.’s right-of-way;

•

the tree showed some evidence of insect damage, damage at the top of the tree from porcupines, a small area of scarring where a lateral branch/leader (LBL) had broken off in the past, and some past signs of Gall Rust disease.

The DNR report concluded as follows: “It is my opinion that because of the unusual configuration of the tree, and its proximity to the powerline, a closer inspection was warranted. A nearer inspection of the tree should have revealed the cut LBL ends and its previous failure, and necessitated determination of the failure potential of the adjacent LBL, implicated in starting the Babb Road Fire.”

The DNR report acknowledged that, other than the multi-dominant nature of the tree, the conditions mentioned above would not have been easily visible without close-up inspection of, or cutting into, the tree. The report also acknowledged that, while the presence of multiple tops would have been visible from the nearby roadway, the tree did not fail at a v-fork due to the presence of multiple tops. The Company contends that applicable inspection standards did not require a closer inspection of the otherwise healthy tree, nor was the Company negligent with respect to its maintenance, inspection or vegetation management practices.

Eleven lawsuits have been filed in connection with the Babb Road fire. Asplundh Tree Company and CNUC Utility Consulting, which both perform vegetation management services as independent contractors to the Company, are also named as defendants in each of the lawsuits. The lawsuits include six subrogation actions filed by insurance companies seeking to recover approximately $23 million purportedly paid to insureds to date; four actions on behalf of individual plaintiffs seeking unspecified damages; and a class action lawsuit seeking unspecified damages. All proceedings, except for one action filed on September 1, 2023 on behalf of three individual plaintiffs, have been consolidated in the Superior Court of Spokane County Washington under the lead action Blakeley v. Avista Corporation et al., and variously assert causes of action for negligence, private nuisance, and trespass (the Blakeley Proceeding).

In November 2023, all parties to the Blakeley Proceeding agreed to a stipulated order, which was presented to and entered by the Superior Court of Spokane County, Washington. The order consolidates the Blakeley Proceeding for trial (in addition to discovery and pre-trial proceedings) and bifurcates the trial into liability and damages phases, such that the initial trial in the case will focus solely on whether the defendants are legally responsible for the Babb Road Fire. A trial date on the liability phase has been set for May 5, 2025.

In addition, the order memorializes the plaintiffs' agreement to voluntarily dismiss all claims asserting inverse condemnation as a theory of liability without prejudice to their ability to seek permission from the Court to refile those claims at a later date if there is good cause to do so. The individual action that was not consolidated into the Blakeley Proceeding does not include claims for inverse condemnation. The parties to the Blakeley Proceeding agreed to a preliminary mediation no later than 60 days prior to the liability trial, and, if there is a trial following that mediation and if the jury returns a verdict in the plaintiffs' favor in the liability trial, a second mediation within 90 days following the verdict focusing on damages. Finally, the plaintiffs agreed to complete a damages questionnaire identifying all claimed damages being sought in connection with the litigation.

The Company will vigorously defend itself in the legal proceedings; however, at this time the Company is unable to predict the likelihood of an adverse outcome or estimate a range of potential loss in the event of such an outcome.

Orofino Fire

In August 2023, a fire subsequently referred to as the "Hospital Fire", started in windy conditions near Orofino, Idaho, burning 3 acres and seven primary residences, as well as several outbuildings. The Idaho Department of Lands investigated and has issued a report in which it concluded the fire was caused by an electrical fault igniting three separate spots which then spread uphill. The Company has a distribution line in the area near the ignition point. While the Company has not yet completed its own investigation, the Company has to date found no evidence suggesting negligence on its part. Except for one claim for damage to personal property, the Company has not, at this time, received any claims in connection with the fire. The Company will vigorously defend itself in the event any such claims are asserted; however, at this time, it is unable to estimate the likelihood of an adverse outcome nor the amount or range of a potential loss in the event of an adverse outcome.

Colstrip

Colstrip Owners Arbitration and Litigation

Colstrip Units 3 and 4 are owned by the Company, PacifiCorp, Portland General Electric (PGE), and Puget Sound Energy (PSE) (collectively, the "Western Co-Owners"), as well as NorthWestern and Talen Montana, LLC (Talen), as tenants in common under an Ownership and Operating Agreement, dated May 6, 1981, as amended (O&O Agreement), in the percentages set forth below:


Co-Owner	Unit 3			Unit 4
Avista		15	%		15	%
PacifiCorp		10	%		10	%
PGE		20	%		20	%
PSE		25	%		25	%
NorthWestern		—			30	%
Talen		30	%		—

Colstrip Units 1 and 2, owned by PSE and Talen, were shut down in 2020 and are in the process of being decommissioned. The co-owners of Units 3 and 4 also own undivided interests in facilities common to both Units 3 and 4, as well as in certain facilities common to all four Colstrip units.

The Washington Clean Energy Transformation Act (CETA), among other things, imposes deadlines by which each electric utility must eliminate from its electricity rates in Washington the costs and benefits associated with coal-fired resources, such as Colstrip. The practical impact of CETA is electricity from such resources, including Colstrip, may no longer be delivered to Washington retail customers after 2025.

The co-owners of Colstrip Units 3 and 4 have differing needs for the generating capacity of these units. Accordingly, certain business disagreements have arisen among the co-owners, including, disagreements as to the requirements for shutting down these units. NorthWestern has initiated arbitration pursuant to the O&O Agreement to resolve these business disagreements, and two actions have been initiated to compel arbitration of those disputes: one by Talen in the Montana Thirteenth Judicial District Court for Yellowstone County, and one by the Western Co-Owners, which is pending in Montana Federal District Court. In light of the ownership transfer agreements discussed below, the Colstrip owners agreed to stay both the litigation and the arbitration through March 2024.

Agreement Between Talen and Puget Sound Energy

In September 2022, PSE and Talen entered into an agreement through which PSE has agreed to transfer its 25 percent ownership in Colstrip Units 3 and 4 to Talen at the end of 2025. The terms and conditions of the agreement are similar in most respects to the NorthWestern transaction discussed below.

Agreement Between Avista and NorthWestern

In January 2023, the Company entered into an agreement with NorthWestern under which, subject to the terms and conditions specified in the agreement, the Company will transfer its 15 percent ownership in Colstrip Units 3 and 4 to NorthWestern. There is no monetary exchange included in the transaction. The transaction is scheduled to close on December 31, 2025 or such other date as the parties mutually agree upon.

Under the agreement, the Company will remain obligated through the close of the transaction to pay its share of (i) operating expenses, (ii) capital expenditures, but not in excess of the portion allocable pro rata to the portion of useful life (through 2030) expired through the close of the transaction, and (iii) except for certain costs relating to post-closing activities, site remediation expenses. In addition, the Company would enter into an agreement under which it would retain its voting rights with respect to decisions relating to remediation.

The Company will retain its Colstrip transmission system assets, which are excluded from the transaction.

Under the Colstrip O&O Agreement, each of the other owners of Colstrip has a 90-day period in which to evaluate the transaction and determine whether to exercise their respective rights of first refusal as to a portion of the generation being turned over to NorthWestern. That period has now expired, and no owners have exercised a right to first refusal.

The transaction is subject to the satisfaction of customary closing conditions including the receipt of any required regulatory approvals, as well as NorthWestern's ability to enter into a new coal supply agreement by December 31, 2024.

The Company does not expect this transaction to have a direct material impact on its financial results.

Burnett et al. v. Talen et al.

Multiple property owners initiated a legal proceeding (titled Burnett et al. v. Talen et al.) in the Montana District Court for Rosebud County against Talen, PSE, PacifiCorp, PGE, Avista Corp., NorthWestern, and Westmoreland Rosebud Mining. The plaintiffs allege a failure to contain coal dust in connection with the operation of Colstrip, and seek unspecified damages. The Company will vigorously defend itself in the litigation, but at this time is unable to predict the outcome, nor an amount or range of potential impact in the event of an outcome adverse to the Company’s interests.

Westmoreland Mine Permits

Two lawsuits have been commenced by the Montana Environmental Information Center and others, challenging certain permits relating to the operation of the Westmoreland Rosebud Mine, which provides coal to Colstrip. In the first, the Montana District Court for Rosebud County issued an order vacating a permit for one area of the mine, which decision was subsequently upheld by the Montana Supreme Court. In the second, the Montana Federal District Court vacated a decision by the federal Office of Surface Mining Reclamation and Enforcement, a branch of the United States Department of Interior, approving expansion of the mine into a new area, pending further analysis of potential environmental impact. An initial appeal of that decision to the Ninth Circuit was dismissed for lack of jurisdiction, pending further proceedings before the Department of the Interior. Avista Corp. is not a party to either of these proceedings, but continues to monitor the progress of both issues and assess the impact, if any, of the proceedings on Westmoreland’s ability to meet its contractual coal supply obligations.

National Park Service (NPS) - Natural and Cultural Damage Claim

In March 2017, the Company accessed property managed by the National Park Service (NPS) to prevent the imminent failure of a power pole surrounded by flood water in the Spokane River. The Company voluntarily reported its actions to the NPS several days later. Thereafter, in March 2018, the NPS notified the Company that it might seek recovery for unspecified costs and damages allegedly caused during the incident pursuant to the System Unit Resource Protection Act (SURPA), 54 U.S.C. 100721 et seq. In January 2021, the United States Department of Justice (DOJ) requested the Company and the DOJ renew discussions relating to the matter. In July 2021, the DOJ communicated that it may seek damages of approximately $2 million in connection with the incident for alleged damage to “natural and cultural resources”. In addition, the DOJ indicated that it may seek treble damages under the SURPA and state law, bringing its total potential claim to approximately $6 million.

The Company disputes the position taken by the DOJ with respect to the incident, as well as the nature and extent of the DOJ’s alleged damages, and will vigorously defend itself in any litigation that may arise with respect to the matter. The Company and the DOJ have engaged in discussions to understand their respective positions and determine whether a resolution of the dispute may be possible. However, the Company cannot predict the outcome of the matter.

Rathdrum, Idaho Natural Gas Incident

In October 2021, there was an incident in Rathdrum, Idaho involving the Company’s natural gas infrastructure. The incident occurred after a third party damaged those facilities during excavation work. The incident resulted in a fire which destroyed one residence and resulted in minor injuries to the occupants. In January 2023, the Company was served with a lawsuit filed in the District Court of Kootenai County, Idaho by one property owner, seeking unspecified damages. In February 2024, the Company became aware of a second lawsuit filed by the owners of the adjacent property, seeking damages for personal injury and emotional distress from having witnessed the incident. The Company intends to vigorously defend itself in both actions.

Other Contingencies

In the normal course of business, the Company has various other legal claims and contingent matters outstanding. The Company believes any ultimate liability arising from these actions will not have a material impact on its financial condition, results of operations or cash flows. It is possible a change could occur in the Company’s estimates of the probability or amount of a liability being incurred. Such a change, should it occur, could be significant.

The Company routinely assesses, based on studies, expert analysis and legal reviews, its contingencies, obligations and commitments for remediation of contaminated sites, including assessments of ranges and probabilities of recoveries from other responsible parties who either have or have not agreed to a settlement as well as recoveries from insurance carriers. The Company’s policy is to accrue and charge to current expense identified exposures related to environmental remediation sites based on estimates of investigation, cleanup and monitoring costs to be incurred.

The Company has potential liabilities under the Endangered Species Act and similar state statutes for species of fish, plants and wildlife that have either already been added to the endangered species list, listed as “threatened” or petitioned for listing. Thus far, measures adopted and implemented have had minimal impact on the Company. However, the Company will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to these issues.

Under the federal licenses for its hydroelectric projects, the Company is obligated to protect its property rights, including water rights. In addition, the Company holds additional non-hydro water rights. The States of Montana and Idaho are each conducting general adjudications of water rights in areas that include the Company's facilities in these states. Claims within the Clark Fork River basin and the Spokane River basin could adversely affect the energy production of the Company's hydroelectric facilities. The Company is and will continue to be a participant in the adjudication processes. The complexity of such adjudications makes each unlikely to be concluded in the foreseeable future. As such, it is not possible for the Company to estimate the impact of any outcome at this time. The Company will continue to seek recovery, through the ratemaking process, of all costs related to this issue.

Regulatory Matters - Schedule of Decoupling and Earnings Sharing Mechanisms (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
WASHINGTON \| Decoupling Rebate [Member]
Schedule of Decoupling and Earnings Sharing [Line Items]
Regulatory Liabilities	$ (3,232)	$ (13,210)
IDAHO \| Decoupling Rebate [Member]
Schedule of Decoupling and Earnings Sharing [Line Items]
Regulatory Liabilities	(7,961)	(7,889)
IDAHO \| Revenue Subject to Refund [Member]
Schedule of Decoupling and Earnings Sharing [Line Items]
Regulatory Liabilities	(572)	(686)
OREGON \| Decoupling Surcharge [Member]
Schedule of Decoupling and Earnings Sharing [Line Items]
Regulatory assets		$ 2,853
OREGON \| Decoupling Rebate [Member]
Schedule of Decoupling and Earnings Sharing [Line Items]
Regulatory Liabilities	$ (3,724)

Pension Plans and Other Postretirement Benefit Plans - Investment Allocation Percentages By Asset Classes (Details)	Dec. 31, 2023	Dec. 31, 2022
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	55.00%	55.00%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	40.00%	40.00%
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	5.00%	5.00%

Equity Investments (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Summary of Equity Investments

The following table summarizes Avista Corp.’s equity investments, which are included in “Other property and investments- net and other non-current assets” on the Consolidated Balance Sheets as of December 31 (dollars in thousands):


	2023		2022
Equity method investments	$	78,513	$	70,196
Investments without readily determinable fair value
Non-recurring fair value		24,583		23,329
Recurring fair value		50,254		54,284
Total	$	153,350	$	147,809

Summary of Net Unrealized Gains Related to Investments without Readily Determinable Fair Value

The following table summarizes net unrealized gains (losses) related to investments without readily determinable fair value held as of the end of the respective period for the years ended December 31 (dollars in thousands):


	2023			2022		2021
Investments recorded at non-recurring fair value	$	—		$	12,285	$	8,761
Investments recorded at recurring fair value		(4,323	)		33,382		—
Total	$	(4,323	)	$	45,667	$	8,761

Net unrealized gains recorded related to investments recorded at non-recurring fair value result from identified observable transactions.

Property, Plant And Equipment - Schedule of Major Classifications of Property, Plant And Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Public Utility, Property, Plant and Equipment [Line Items]
Construction work-in-progress (CWIP) and other	$ 179,527	$ 164,147
Total	7,979,008	7,725,835
Other Property	393,985	365,085
Total	7,985,433	7,742,466
Avista Utilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	7,786,150	7,545,007
Common Plant	759,498	744,173
Avista Utilities [Member] \| Electricity [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production	1,498,398	1,593,795
Transmission	1,059,389	994,709
Distribution	2,383,201	2,236,376
Construction work-in-progress (CWIP) and other	394,711	376,981
Total	5,335,699	5,201,861
Avista Utilities [Member] \| Natural Gas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	1,539,467	1,452,637
Construction work-in-progress (CWIP) and other	91,492	88,264
Total	1,690,953	1,598,973
Natural gas underground storage	59,994	58,072
Alaska Electric Light & Power [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	192,858	180,828
Common Plant	10,340	10,018
Alaska Electric Light & Power [Member] \| Electricity [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production	118,817	106,390
Transmission	22,827	22,856
Distribution	32,322	29,269
Construction work-in-progress (CWIP) and other	8,552	12,295
Total	182,518	170,810
Corporate and Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other Property	$ 6,425	$ 16,631

Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended			12 Months Ended
	Apr. 30, 2022 USD ($) a	Jul. 31, 2021 USD ($)	Aug. 31, 2019 USD ($)	Dec. 31, 2023 USD ($) Lawsuit Plaintiff	Aug. 31, 2023 a	Jan. 16, 2023	Sep. 30, 2022	May 31, 2021 a Building
Loss Contingencies [Line Items]
Owners percentage interest				15.00%
Collective Bargaining Agreements Avista Utilities Employees [Member] \| IBEW [Member]
Loss Contingencies [Line Items]
Percentage of employees represented				36.00%
Collective Bargaining Agreements Avista Utilities Bargaining Unit Employees [Member] \| IBEW [Member]
Loss Contingencies [Line Items]
Percentage of largest group of employees represented				90.00%
Collective Bargaining Agreements [Member] \| IBEW [Member]
Loss Contingencies [Line Items]
Agreement term				4 years
Agreement expiration month and year				2025-03
Natural and Cultural Damage Claim [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value		$ 2.0
Boyds Fire [Member] \| Damage from Fire [Member] \| Maximum [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value			$ 4.4
Babb Road Fire [Member] \| Damage from Fire [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value				$ 23.0
Number of residential, commercial and other structures impacted \| Building								220
Road fire covered area \| a								15,000
Number of subrogation actions filed \| Lawsuit				6
Number of actions on behalf of individual plaintiffs \| Plaintiff				4
System Unit Resource Protection Act [Member] \| Natural and Cultural Damage Claim [Member]
Loss Contingencies [Line Items]
Increased potential claim		$ 6.0
Colstrip [Member]
Loss Contingencies [Line Items]
Agreement voting requirement				NorthWestern has initiated arbitration pursuant to the O&O Agreement to resolve these business disagreements, and two actions have been initiated to compel arbitration of those disputes: one by Talen in the Montana Thirteenth Judicial District Court for Yellowstone County, and one by the Western Co-Owners, which is pending in Montana Federal District Court. In light of the ownership transfer agreements discussed below, the Colstrip owners agreed to stay both the litigation and the arbitration through March 2024
Orofino Fire [Member] \| Damage from Fire [Member]
Loss Contingencies [Line Items]
Road fire covered area \| a					3
Avista Corp [Member] \| Road 11 Fire [Member] \| Damage from Fire [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value	$ 5.0
Road fire covered area \| a	10,000
PSE [Member] \| Colstrip [Member] \| Unit 3 [Member]
Loss Contingencies [Line Items]
Owners percentage interest				25.00%
PSE [Member] \| Colstrip [Member] \| Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest				25.00%			25.00%
NorthWestern [Member] \| Colstrip [Member] \| Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest				30.00%		15.00%

Leases - Summary of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Operating Leases, Liability, Payments, Due year one	$ 4,988	$ 4,850
Operating Leases, Liability, Payments, Due year two	4,984	4,877
Operating Leases, Liability, Payments, Due year three	4,981	4,884
Operating Leases, Liability, Payments, Due year four	5,007	4,869
Operating Leases, Liability, Payments, Due year five	4,992	4,880
Operating Leases, Thereafter	83,532	86,991
Operating Leases, Total lease payments	108,484	111,351
Operating Leases, Less: imputed interest	(40,435)	(42,718)
Operating Leases, Total	$ 68,049	$ 68,633
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Liabilities	Liabilities
Finance Leases, Liability, Payments, Due year one	$ 5,459	$ 5,456
Finance Leases, Liability, Payments, Due year two	5,454	5,459
Finance Leases, Liability, Payments, Due year three	5,456	5,454
Finance Leases, Liability, Payments, Due year four	5,458	5,456
Finance Leases, Liability, Payments, Due year five	5,456	5,458
Finance Leases, Thereafter	27,292	32,748
Finance Leases, Total lease payments	54,575	60,031
Finance Leases, Less: imputed interest	(12,080)	(14,301)
Finance Leases, Total	$ 42,495	$ 45,730

Short-Term Borrowings - Schedule of Balances Outstanding and Interest Rates of Borrowings (Details) - Avista Utilities [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Balance outstanding at end of period	$ 349,000	$ 313,000
Letters of credit outstanding at end of period	$ 4,700	$ 35,563
Average interest rate at end of period	6.46%	5.31%

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

Line of Credit Facility [Line Items]

Short-Term Borrowings (Tables)

12 Months Ended

Dec. 31, 2023

Schedule of Balances Outstanding and Interest Rates of Borrowings

Balances outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed line of credit were as follows as of December 31 (dollars in thousands):


	2023			2022
Balance outstanding at end of period	$	349,000		$	313,000
Letters of credit outstanding at end of period		4,700			35,563
Average interest rate at end of period		6.46	%		5.31	%

Fair Value - Schedule of Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease Obligation	$ 42,495	$ 45,730
Level 2 [Member] \| Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,100,000	1,113,500
Level 2 [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	968,893	966,881
Level 3 [Member] \| Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,450,000	1,200,000
Level 3 [Member] \| Reported Value Measurement [Member] \| Alaska Electric Light & Power [Member] \| Finance Lease [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease Obligation	42,495	45,730
Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,166,512	881,480
Level 3 [Member] \| Estimate of Fair Value Measurement [Member] \| Alaska Electric Light & Power [Member] \| Finance Lease [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease Obligation	39,600	41,700
Affiliated Entity [Member] \| Level 3 [Member] \| Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	51,547	51,547
Affiliated Entity [Member] \| Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 46,098	$ 42,836

Accounting For Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal income taxes at statutory rates	$ 28,886	$ 28,977	$ 33,467
Tax effect of regulatory treatment of utility plant differences	(12,270)	(12,366)	(13,820)
State income tax expense	2,077	1,676	1,385
Flow through related to deduction of meters and mixed service costs	(47,983)	(34,454)	(8,678)
Tax credits	(2,334)	(258)	(75)
Other	(2,006)	(766)	(248)
Total income tax expense (benefit)	$ (33,630)	$ (17,191)	$ 12,031
Federal statutory tax rate	21.00%	21.00%	21.00%	21.00%	35.00%
Tax effect of regulatory treatment of utility plant differences	(8.90%)	(9.00%)	(8.70%)
State income tax expense	1.50%	1.20%	0.80%
Flow through related to deduction of meters and mixed service costs	(34.90%)	(25.00%)	(5.40%)
Tax credits	(1.70%)	(0.20%)
Other	(1.40%)	(0.50%)	(0.20%)
Effective Income Tax Rate Reconciliation, Percent	(24.40%)	(12.50%)	7.50%

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Alternative revenue programs	$ 4,899	$ (33,357)	$ (6,635)
Total utility revenues	1,750,996	1,709,519	1,438,365
Non-utility revenues	558	688	571
Total operating revenues	1,751,554	1,710,207	1,438,936
Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	445,490	434,490	413,657
Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	370,549	364,438	352,034
Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	109,689	107,740	106,756
Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	8,243	7,737	7,722
Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	933,971	914,405	880,169
Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	32,941	32,307	21,005
Other Electric Revenues from Contracts With Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	45,332	49,920	33,870
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	1,012,244	996,632	935,044
Avista Utilities [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	1,485,510	1,400,027	1,233,904
Derivative revenues	199,133	286,309	152,590
Alternative revenue programs	4,899	(33,357)	(6,635)
Deferrals and amortizations for rate refunds to customers	1,026	207	2,984
Other utility revenues	12,289	10,629	10,156
Total utility revenues	1,702,857	1,663,815	1,392,999
Avista Utilities [Member] \| Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	425,258	414,823	394,717
Avista Utilities [Member] \| Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	343,523	338,656	326,173
Avista Utilities [Member] \| Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	109,689	107,740	106,756
Avista Utilities [Member] \| Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	7,976	7,483	7,472
Avista Utilities [Member] \| Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	886,446	868,702	835,118
Avista Utilities [Member] \| Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	32,941	32,307	21,005
Avista Utilities [Member] \| Other Electric Revenues from Contracts With Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	45,332	49,920	33,870
Avista Utilities [Member] \| Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	964,719	950,929	889,993
Avista Utilities [Member] \| Residential Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	325,631	284,452	221,405
Avista Utilities [Member] \| Commercial Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	164,048	139,923	100,819
Avista Utilities [Member] \| Industrial and Interruptible Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	17,315	10,471	7,796
Avista Utilities [Member] \| Retail Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	506,994	434,846	330,020
Avista Utilities [Member] \| Transportation Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	8,172	8,627	8,547
Avista Utilities [Member] \| Other Natural Gas Revenues from Contracts With Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	5,625	5,625	5,344
Avista Utilities [Member] \| Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	520,791	449,098	343,911
Alaska Electric Light & Power [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	47,525	45,703	45,051
Deferrals and amortizations for rate refunds to customers		(614)	(190)
Other utility revenues	614	615	505
Total utility revenues	48,139	45,704	45,366
Alaska Electric Light & Power [Member] \| Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20,232	19,667	18,940
Alaska Electric Light & Power [Member] \| Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	27,026	25,782	25,861
Alaska Electric Light & Power [Member] \| Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	267	254	250
Alaska Electric Light & Power [Member] \| Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	47,525	45,703	45,051
Alaska Electric Light & Power [Member] \| Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	47,525	45,703	45,051
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax			2
Non-utility revenues	558	688	571
Corporate and Other [Member] \| Other Revenues
Disaggregation of Revenue [Line Items]
Non-utility revenues	$ 558	$ 688	$ 569

Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net income	$ 171,180	$ 155,176	$ 147,334
Denominator:
Weighted-average number of common shares outstanding-basic	76,396	72,989	69,951
Effect of dilutive securities:
Performance and restricted stock awards	100	104	134
Weighted-average number of common shares outstanding-diluted	76,495	73,093	70,085
Earnings per common share:
Basic	$ 2.24	$ 2.13	$ 2.11
Diluted	$ 2.24	$ 2.12	$ 2.1

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]
Beginning Balance at Dec. 31, 2020		$ 1,286,068	$ (14,378)	$ 758,036
Beginning Balance (in shares) at Dec. 31, 2020		69,238,901
Issuance of common stock through equity compensation plans		$ 931
Shares issued through equity compensation plans		93,806
Issuance of common stock through Employee Investment Plan		$ 610
Shares issued through Employee Investment Plan		14,480
Issuance of common stock through sales agency agreements, net of issuance costs		$ 88,457
Shares issued through sales agency agreements		2,150,336
Equity compensation expense		$ 5,180
Payment of minimum tax withholdings for share-based payment awards		(993)
Other		(101)
Other comprehensive income	$ 3,339		3,339
Net Income (Loss)	147,334			147,334
Dividends on common stock				(119,739)
Ending Balance at Dec. 31, 2021	$ 2,154,744	$ 1,380,152	(11,039)	785,631
Ending Balance (in shares) at Dec. 31, 2021		71,497,523
Dividends declared per common share	$ 1.69
Issuance of common stock through equity compensation plans		$ 1,150
Shares issued through equity compensation plans		123,631
Issuance of common stock through Employee Investment Plan		$ 605
Shares issued through Employee Investment Plan		14,306
Issuance of common stock through sales agency agreements, net of issuance costs		$ 137,173
Shares issued through sales agency agreements		3,310,488
Equity compensation expense		$ 7,567
Payment of minimum tax withholdings for share-based payment awards		(1,462)
Other comprehensive income	$ 8,981		8,981
Net Income (Loss)	155,176			155,176
Dividends on common stock				(129,266)
Ending Balance at Dec. 31, 2022	$ 2,334,668	$ 1,525,185	(2,058)	811,541
Ending Balance (in shares) at Dec. 31, 2022	74,945,948	74,945,948
Dividends declared per common share	$ 1.76
Issuance of common stock through equity compensation plans		$ 1,298
Shares issued through equity compensation plans		117,450
Issuance of common stock through Employee Investment Plan		$ 460
Shares issued through Employee Investment Plan		11,943
Issuance of common stock through sales agency agreements, net of issuance costs		$ 111,848
Shares issued through sales agency agreements		2,999,246
Equity compensation expense		$ 7,144
Payment of minimum tax withholdings for share-based payment awards		(1,497)
Other		(111)
Other comprehensive income	$ 1,701		1,701
Net Income (Loss)	171,180			171,180
Dividends on common stock				(141,368)
Ending Balance at Dec. 31, 2023	$ 2,485,323	$ 1,644,327	$ (357)	$ 841,353
Ending Balance (in shares) at Dec. 31, 2023	78,074,587	78,074,587
Dividends declared per common share	$ 1.84

Commitments And Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Ownership and Operating Ownership Interest Percentage


Co-Owner	Unit 3			Unit 4
Avista		15	%		15	%
PacifiCorp		10	%		10	%
PGE		20	%		20	%
PSE		25	%		25	%
NorthWestern		—			30	%
Talen		30	%		—

Accumulated Other Comprehensive Loss - Reclassification out of Accumulated Other Comprehensive Loss (Details) - Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net prior service cost	$ (558)	$ (4,095)	$ (793)
Amortization of net loss	18,872	57,650	38,070
Adjustment due to effects of regulation	(16,161)	(42,187)	(33,050)
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, before tax	2,153	11,368	4,227
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, tax	(452)	(2,387)	(888)
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, after tax	$ 1,701	$ 8,981	$ 3,339

Derivatives and Risk Management

12 Months Ended

Dec. 31, 2023

Derivative Instruments and Hedges, Assets [Abstract]

Derivatives and Risk Management

NOTE 8. DERIVATIVES AND RISK MANAGEMENT

Energy Commodity Derivatives

Avista Corp. is exposed to market risks relating to changes in electricity and natural gas commodity prices and certain other fuel prices. Market risk is, in general, the risk of fluctuation in the market price of the commodity being traded and is influenced primarily by supply and demand. Market risk includes the fluctuation in the market price of associated derivative commodity instruments. Avista Corp. utilizes derivative instruments, such as forwards, futures, swap derivatives and options to manage the various risks relating to these commodity price exposures. Avista Corp. has an energy resources risk policy and control procedures to manage these risks.

As part of Avista Corp.'s resource procurement and management operations in the electric business, Avista Corp. engages in an ongoing process of resource optimization, which involves the economic selection from available energy resources to serve Avista Corp.'s load obligations and the use of these resources to capture available economic value through wholesale market transactions. These include sales and purchases of electric capacity and energy, fuel for electric generation, and derivative contracts related to capacity, energy and fuel. Such transactions are part of the process of matching resources with load obligations and hedging a portion of the related financial risks. These transactions range from terms of intra-hour up to multiple years.

As part of its resource procurement and management of its natural gas business, Avista Corp. makes continuing projections of its natural gas loads and assesses available natural gas resources including natural gas storage availability. Natural gas resource planning typically includes peak requirements, low and average monthly requirements and delivery constraints from natural gas supply locations to Avista Corp.'s distribution system. However, daily variations in natural gas demand can be significantly different than monthly demand projections. Based on these projections, Avista Corp. plans and executes a series of transactions to hedge a portion of its projected natural gas requirements through forward market transactions and derivative instruments. These transactions may extend as much as three natural gas operating years (November through October) into the future. Avista Corp. also leaves a significant portion of its natural gas supply requirements unhedged for purchase in short-term and spot markets.

Avista Corp. plans for sufficient natural gas delivery capacity to serve its retail customers for a theoretical peak day event. Avista Corp. generally has more pipeline and storage capacity than what is needed during periods other than a peak day. Avista Corp. optimizes its natural gas resources by using market opportunities to generate economic value that mitigates the fixed costs. Avista Corp. also optimizes its natural gas storage capacity by purchasing and storing natural gas when prices are traditionally lower, typically in the summer, and withdrawing during higher priced months, typically during the winter. However, if market conditions and prices indicate that Avista Corp. should buy or sell natural gas at other times during the year, Avista Corp. engages in optimization transactions to capture value in the marketplace. Natural gas optimization activities include, but are not limited to, wholesale market sales of surplus natural gas supplies, purchases and sales of natural gas to optimize use of pipeline and storage capacity, and participation in the transportation capacity release market.

The following table presents the underlying energy commodity derivative volumes as of December 31, 2023 expected to be delivered in each respective year (in thousands of MWhs and mmBTUs):


	Purchases								Sales
	Electric Derivatives				Gas Derivatives				Electric Derivatives				Gas Derivatives
Year	Physical (1) MWh		Financial (1) MWh		Physical (1) mmBTUs		Financial (1) mmBTUs		Physical (1) MWh		Financial (1) MWh		Physical (1) mmBTUs		Financial (1) mmBTUs
2024		9		—		22,747		74,596		472		510		1,723		12,038
2025		—		—		12,505		19,590		11		96		1,115		1,125
2026		—		—		5,570		3,940		—		—		—		—

As of December 31, 2023, there are no expected deliveries of energy commodity derivatives after 2026.

The following table presents the underlying energy commodity derivative volumes as of December 31, 2022 that were expected to be delivered in each respective year (in thousands of MWhs and mmBTUs):


	Purchases								Sales
	Electric Derivatives				Gas Derivatives				Electric Derivatives				Gas Derivatives
Year	Physical (1) MWh		Financial (1) MWh		Physical (1) mmBTUs		Financial (1) mmBTUs		Physical (1) MWh		Financial (1) MWh		Physical (1) mmBTUs		Financial (1) mmBTUs
2023		5		—		19,140		79,253		136		1,011		4,145		29,473
2024		—		—		533		30,658		—		—		1,370		9,668
2025		—		—		450		4,895		—		—		1,115		1,125

As of December 31, 2022, there were no expected deliveries of energy commodity derivatives after 2025.

(1)

the benefit or cost but with no physical delivery of the commodity, such as futures, swap derivatives, options, or forward contracts.

The electric and natural gas derivative contracts above will be included in either power supply costs or natural gas supply costs during the period they are scheduled to be delivered and will be included in the various deferral and recovery mechanisms (ERM, PCA, and PGAs), or in the general rate case process, and are expected to be recovered through retail rates from customers.

Foreign Currency Exchange Derivatives

A significant portion of Avista Corp.'s natural gas supply (including fuel for power generation) is obtained from Canadian sources. Most of those transactions are executed in U.S. dollars, which avoids foreign currency risk. A portion of Avista Corp.’s short-term natural gas transactions and long-term Canadian transportation contracts are committed based on Canadian currency prices. The short term natural gas transactions are settled within 60 days with U.S. dollars. Avista Corp. hedges a portion of the foreign currency risk by purchasing Canadian currency exchange derivatives when such commodity transactions are initiated. The foreign currency exchange derivatives and the unhedged foreign currency risk have not had a material effect on Avista Corp.’s financial condition, results of operations or cash flows and these differences in cost related to currency fluctuations are included with natural gas supply costs for ratemaking.

The following table summarizes the foreign currency exchange derivatives outstanding as of December 31 (dollars in thousands):


	2023		2022
Number of contracts		5		19
Notional amount (in United States dollars)	$	81	$	8,563
Notional amount (in Canadian dollars)		109		11,659

Interest Rate Swap Derivatives

Avista Corp. is affected by fluctuating interest rates related to a portion of its existing debt, and future borrowing requirements. Avista Corp. may hedge a portion of its interest rate risk with financial derivative instruments, including interest rate swap derivatives. These interest rate swap derivatives are considered economic hedges against fluctuations in future cash flows associated with anticipated debt issuances.

The following table summarizes the unsettled interest rate swap derivatives outstanding as of the balance sheet date indicated below (dollars in thousands):


Balance Sheet Date	Number of Contracts		Notional Amount		Mandatory Cash Settlement Date
December 31, 2023		2	$	20,000	2024
		1		10,000	2025
December 31, 2022		4	$	40,000	2023
		1		10,000	2024

The fair value of outstanding interest rate swap derivatives can vary significantly from period to period depending on the total notional amount of swap derivatives outstanding and fluctuations in market interest rates compared to the interest rates fixed by the swaps. Avista Corp. is required to make cash payments to settle the interest rate swap derivatives when the fixed rates are higher than prevailing market rates at the date of settlement. Conversely, Avista Corp. receives cash to settle its interest rate swap derivatives when prevailing market rates at the time of settlement exceed the fixed swap rates.

Summary of Outstanding Derivative Instruments

The amounts recorded on the Consolidated Balance Sheets as of December 31, 2023 and December 31, 2022 reflect the offsetting of derivative assets and liabilities where a legal right of offset exists.

The following table presents the fair values and locations of derivative instruments recorded on the Consolidated Balance Sheets as of December 31, 2023 (dollars in thousands):


	Fair Value
Derivative and Balance Sheet Location	Gross Asset		Gross Liability			Collateral Netting		Net Asset (Liability) on Balance Sheet
Foreign currency exchange derivatives
Other current assets	$	2	$	—		$	—	$	2
Interest rate swap derivatives
Other current assets		3,667		—			—		3,667
Other non-current liabilities and deferred credits		—		(182	)		—		(182	)
Energy commodity derivatives
Other current assets		8,531		(379	)		—		8,152
Other current liabilities		19,510		(79,082	)		42,355		(17,217	)
Other non-current liabilities and deferred credits		2,913		(20,633	)		—		(17,720	)
Total derivative instruments recorded on the balance sheet	$	34,623	$	(100,276	)	$	42,355	$	(23,298	)

The following table presents the fair values and locations of derivative instruments recorded on the Consolidated Balance Sheets as of December 31, 2022 (dollars in thousands):


	Fair Value
Derivative and Balance Sheet Location	Gross Asset		Gross Liability			Collateral Netting		Net Asset (Liability) on Balance Sheet
Foreign currency exchange derivatives
Other current assets	$	43	$	—		$	—	$	43
Other current liabilities		—		(3	)		—		(3	)
Interest rate swap derivatives
Other current assets		8,536		—			—		8,536
Other property and investments-net and other non-current assets		2,648		—			—		2,648
Other current liabilities		—		(52	)		—		(52	)
Energy commodity derivatives
Other current assets		32,257		(22,638	)		—		9,619
Other property and investments-net and other non-current assets		312		(16	)		—		296
Other current liabilities		107,902		(229,607	)		94,850		(26,855	)
Other non-current liabilities and deferred credits		6,049		(24,530	)		10,589		(7,892	)
Total derivative instruments recorded on the balance sheet	$	157,747	$	(276,846	)	$	105,439	$	(13,660	)

Exposure to Demands for Collateral

Avista Corp.'s derivative contracts often require collateral (in the form of cash or letters of credit) or other credit enhancements, or reductions or terminations of a portion of the contract through cash settlement. In the event of changes in market prices or a downgrade in Avista Corp.'s credit ratings or other established credit criteria, additional collateral may be required. In periods of price volatility, the level of exposure can change significantly. As a result, sudden and significant demands may be made against Avista Corp.'s credit facilities and cash. Avista Corp. actively monitors the exposure to possible collateral calls and takes steps to mitigate capital requirements.

The following table presents collateral outstanding related to its derivative instruments as of December 31 (dollars in thousands):


	2023		2022
Energy commodity derivatives
Cash collateral posted	$	43,095	$	171,581
Letters of credit outstanding		20,000		49,425
Balance sheet offsetting (cash collateral against net derivative positions)		42,355		105,439

There were no letters of credit outstanding related to interest rate swap derivatives as of December 31, 2023 and December 31, 2022.


	2023
Interest rate swap derivatives
Liabilities with credit-risk-related contingent features	$	182
Additional collateral to post		182
Energy commodity derivatives
Liabilities with credit-risk-related contingent features	$	18,016
Additional collateral to post		15,125

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income , Defined Benefit Plan, after Reclassification Adjustment, Tax	$ 452	$ 2,387	$ (888)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Allowance for Funds Used During Construction

Nature of Business

AERC is a wholly-owned subsidiary of Avista Corp. The primary subsidiary of AERC is AEL&P, which comprises Avista Corp.'s regulated utility operations in Alaska.

Basis of Reporting

Use of Estimates

•

determining the market value of energy commodity derivative assets and liabilities,

•

pension and other postretirement benefit plan obligations,

•

contingent liabilities,

•

goodwill impairment testing,

•

fair value of equity investments,

•

recoverability of regulatory assets, and

•

unbilled revenues.

Regulation

Regulatory Deferred Charges and Credits

The Company prepares its consolidated financial statements in accordance with regulatory accounting practices because:

•

rates for regulated services are established by or subject to approval by independent third-party regulators,

•

the regulated rates are designed to recover the cost of providing the regulated services, and

•

in view of demand for the regulated services and the level of competition, it is reasonable to assume that rates can be charged to and collected from customers at levels that will recover costs.

•

required to write off its regulatory assets, and

•

See Note 23 for further details of regulatory assets and liabilities.

Depreciation


	2023			2022			2021
Avista Utilities		3.52	%		3.50	%		3.54	%
Alaska Electric Light and Power Company		2.78	%		2.78	%		2.77	%

The average service lives for the following broad categories of utility plant in service are (in years):


	Avista Utilities		Alaska Electric Light and Power Company
Electric thermal/other production		26		41
Hydroelectric production		79		42
Electric transmission		50		43
Electric distribution		40		39
Natural gas distribution property		44	N/A
Other shorter-lived general plant		8		18

The effective AFUDC rate was the following for the years ended December 31:


	2023			2022			2021
Avista Utilities		7.03	%		7.12	%		7.19	%
Alaska Electric Light and Power Company		8.61	%		8.08	%		8.90	%

Income Taxes

Stock-Based Compensation


	2023		2022			2021
Stock-based compensation expense	$	7,144	$	7,567		$	4,713
Income tax benefits		1,500		1,589			990
Excess tax benefits (expenses) on settled share-based employee payments		84		(19	)		(909	)


	2023		2022		2021
Restricted Shares
Shares granted during the year		76,806		115,746		62,594
Shares vested during the year		75,007		44,829		34,854
Unvested shares at end of year		152,140		157,860		96,127
Unrecognized compensation expense at end of year (in thousands)	$	3,477	$	3,923	$	2,215
TSR Awards
TSR shares granted during the year		34,912		69,814		64,910
TSR shares vested during the year		61,456		43,730		77,174
TSR shares earned based on market metrics		44,863		48,890		58,652
Unvested TSR shares at end of year		96,915		130,567		107,854
Unrecognized compensation expense at end of year (in thousands)	$	2,235	$	3,533	$	2,653
CEPS Awards
CEPS shares granted during the year		104,685		69,814		64,910
CEPS shares vested during the year		61,456		43,730		38,590
CEPS shares earned based on performance metrics		33,801		—		26,627
Unvested CEPS shares at end of year		161,235		130,567		107,854
Unrecognized compensation expense at end of year (in thousands)	$	2,439	$	2,471	$	1,223

Other Expense (Income) - Net

Other Income - Net

Other income - net consisted of the following items for the years ended December 31 (dollars in thousands):


	2023			2022		2021
Interest income	$	5,949		$	1,957	$	1,943
Interest on regulatory deferrals		8,713			1,914		1,206
Equity-related AFUDC		6,886			6,704		7,004
Non-service portion of pension and other postretirement benefit expenses		630			3,037		(1,386	)
Earnings (losses) on investments		(3,227	)		48,492		21,402
Other income		575			613		3,129
Total	$	19,526		$	62,717	$	33,298

Earnings per Common Share

Cash and Cash Equivalents

For the purposes of the Consolidated Statements of Cash Flows, the Company considers all temporary investments with a maturity of three months or less when purchased to be cash equivalents.

Allowance For Doubtful Accounts

Allowance for Doubtful Accounts


	2023			2022			2021
Allowance as of the beginning of the year	$	6,473		$	10,465		$	11,387
Additions expensed during the year		6,865			149			9,279
Net deductions (1)		(8,351	)		(4,141	)		(10,201	)
Allowance as of the end of the year	$	4,987		$	6,473		$	10,465

(1)

Utility Plant in Service

Asset Retirement Obligations


	2023		2022
Regulatory liability for utility plant retirement costs	$	417,027	$	376,817

Goodwill

Derivative Assets and Liabilities

Derivatives are recorded as either assets or liabilities on the Consolidated Balance Sheets measured at estimated fair value.

Fair Value Measurements

Unamortized Debt Expense

Unamortized debt expense includes debt issuance costs that are amortized over the life of the related debt. These costs are recorded as an offset to Long-Term Debt on the Consolidated Balance Sheets.

Unamortized Debt Repurchase Costs

Appropriated Retained Earnings

The appropriated retained earnings amounts included in retained earnings were as follows as of December 31 (dollars in thousands):


	2023		2022
Appropriated retained earnings	$	59,118	$	57,231

Contingencies

Inventory

Inventories of materials and supplies, emissions allowances, stored natural gas and fuel stock are recorded at average cost and consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Materials and supplies	$	81,651	$	75,766
Emission allowances		56,097		—
Stored natural gas		16,272		26,788
Fuel stock		5,964		5,120
Total	$	159,984	$	107,674

Revenue

12 Months Ended

Dec. 31, 2023

Revenue from Contract with Customer [Abstract]

Revenue

NOTE 4. REVENUE

The core principle of the revenue recognition model is that an entity should identify the various performance obligations in a contract, allocate the transaction price among the performance obligations and recognize revenue when (or as) the entity satisfies each performance obligation.

Utility Revenues

Revenue from Contracts with Customers

General

The majority of Avista Corp.’s revenue is from rate-regulated sales of electricity and natural gas to retail customers, which has two performance obligations, (1) having service available for a specified period (typically a month at a time) and (2) the delivery of energy to customers. The total energy price generally has a fixed component (basic charge) related to having service available and a usage-based component, related to the delivery and consumption of energy. The commodity is sold and/or delivered to and consumed by the customer simultaneously, and the provisions of the relevant utility commission authorization determine the charges the Company may bill the customer. Since all revenue recognition criteria are met upon the delivery of energy to customers, revenue is recognized immediately.

In addition, the sale of electricity and natural gas is governed by the various state utility commissions, which set rates, charges, terms and conditions of service, and prices. Collectively, these rates, charges, terms and conditions are included in a “tariff,” which governs all aspects of the provision of regulated services. Tariffs are only permitted to be changed through a rate-setting process involving an independent, third-party regulator empowered by statute to establish rates that bind customers. Thus, all regulated sales by the Company are conducted subject to the regulator-approved tariff.

Tariff sales involve the current provision of commodity service (electricity and/or natural gas) to customers for a price that generally has a basic charge and a usage-based component. Tariff rates also include certain pass-through costs to customers such as natural gas costs, retail revenue credits and other miscellaneous regulatory items that do not impact net income, but can cause total revenue to fluctuate significantly up or down compared to previous periods. The commodity is sold and/or delivered to and consumed by the customer simultaneously, and the provisions of the relevant tariff determine the charges the Company may bill the customer, payment due date, and other pertinent rights and obligations of both parties. Generally, tariff sales do not involve a written contract. Since all revenue recognition criteria are met upon the delivery of energy to customers, revenue is recognized at that time.

Revenues from contracts with customers are presented in the Consolidated Statements of Income in the line item “Utility revenues, exclusive of alternative revenue programs.”

Unbilled Revenue from Contracts with Customers

The determination of the volume of energy sales to individual customers is based on the reading of their meters, which occurs on a systematic basis throughout the month (once per month for each individual customer). At the end of each calendar month, the amount of energy delivered to customers since the date of the last meter reading is estimated and the corresponding unbilled revenue is estimated and recorded. The Company's estimate of unbilled revenue is based on:

•

the number of customers,

•

tariff rates,

•

meter reading dates,

•

actual native load for electricity,

•

actual throughput for natural gas, and

•

electric line losses and natural gas system losses.

Any difference between actual and estimated revenue is automatically corrected in the following month when the meter reading and customer billing occurs.

Accounts receivable includes unbilled energy revenues of the following amounts as of December 31 (dollars in thousands):


	2023		2022
Unbilled accounts receivable	$	78,531	$	81,691

Non-Derivative Wholesale Contracts

The Company has certain wholesale contracts that are not accounted for as derivatives and are considered revenue from contracts with customers. Revenue is recognized as energy is delivered to the customer or the service is available for specified period of time, consistent with the discussion of rate regulated sales above.

Alternative Revenue Programs (Decoupling)

ASC 606 retained existing GAAP associated with alternative revenue programs, which specified alternative revenue programs are contracts between an entity and a regulator of utilities, not a contract between an entity and a customer. GAAP requires the presentation of revenue arising from alternative revenue programs separately from revenues arising from contracts with customers on the Consolidated Statements of Income. The Company's decoupling mechanisms (also known as a FCA in Idaho) qualify as alternative revenue programs. Decoupling revenue deferrals are recognized in the Consolidated Statements of Income during the period they occur (i.e. during the period of revenue shortfall or excess due to fluctuations in customer usage), subject to certain limitations, and a regulatory asset or liability is established which will be surcharged or rebated to customers in future periods. GAAP requires that for an alternative revenue program, like decoupling, the revenue must be expected to be collected from customers within 24 months of the deferral to qualify for recognition in the Consolidated Statements of Income. Amounts included in the Company's decoupling program that are not expected to be collected from customers within 24 months are not recorded in the financial statements until the period in which revenue recognition criteria are met. The amounts expected to be collected from customers within 24 months represents an estimate made by the Company on an ongoing basis due to it being based on the volumes of electric and natural gas sold to customers on a go-forward basis.

The Company records alternative program revenues under the gross method, which is to amortize the decoupling regulatory asset/liability to the alternative revenue program line item on the Consolidated Statements of Income as it is collected from or refunded to customers. The cash passing between the Company and the customers is presented in revenue from contracts with customers since it is a portion of the overall tariff paid by customers. This method results in a gross-up to both revenue from contracts with customers and revenue from alternative revenue programs, but has a net zero impact on total revenue. Depending on whether the previous deferral balance being amortized was a regulatory asset or regulatory liability, and depending on the size and direction of the current year deferral of surcharges and/or rebates to customers, it could result in negative alternative revenue program revenue during the year.

Derivative Revenue

Most wholesale electric and natural gas transactions (including both physical and financial transactions), and the sale of fuel are considered derivatives, which are disclosed separately from revenue from contracts with customers. Revenue is recognized for these items upon the settlement/expiration of the derivative contract. Derivative revenue includes transactions entered into and settled within the same month.

Other Utility Revenue

Other utility revenue includes rent, sales of materials, late fees and other charges that do not represent contracts with customers. This revenue is excluded from revenue from contracts with customers, as this revenue does not represent items where a customer is a party that has contracted with the Company to obtain goods or services that are an output of the Company’s ordinary activities in exchange for consideration. As such, these revenues are presented separately from revenue from contracts with customers.

Other Considerations for Utility Revenues

Gross Versus Net Presentation

Revenues and resource costs from Avista Utilities’ settled energy contracts “booked out” (not physically delivered) are reported on a net basis as part of derivative revenues.

Utility-related taxes collected from customers (primarily state excise taxes and city utility taxes) are imposed on Avista Utilities as opposed to being imposed on customers; therefore, Avista Utilities is the taxpayer and records these transactions on a gross

basis in revenue from contracts with customers and operating expense (taxes other than income taxes). The utility-related taxes collected from customers at AEL&P are imposed on the customers rather than AEL&P; therefore, the customers are the taxpayers and AEL&P is acting as their agent. As such, these transactions at AEL&P are presented on a net basis within revenue from contracts with customers.

Utility-related taxes included in revenue from contracts with customers were as follows for the years ended December 31 (dollars in thousands):


	2023		2022		2021
Utility-related taxes	$	75,404	$	69,931	$	62,736

Significant Judgments and Unsatisfied Performance Obligations

The only significant judgments involving revenue recognition are estimates surrounding unbilled revenue and receivables from contracts with customers and estimates surrounding the amount of decoupling revenues that will be collected from customers within 24 months (discussed above).

The Company has certain capacity arrangements, where the Company has a contractual obligation to provide either electric or natural gas capacity to its customers for a fixed fee. Most of these arrangements are paid for in arrears by the customers and do not result in deferred revenue and only result in receivables from the customers. The Company has one capacity agreement where the customer makes payments throughout the year. As of December 31, 2023, the Company estimates it had unsatisfied capacity performance obligations of $7.4 million, which will be recognized as revenue in future periods as the capacity is provided to the customers. These performance obligations are not reflected in the financial statements, as the Company has not received payment for these services.

Disaggregation of Total Operating Revenue

The following table disaggregates total operating revenue by segment and source for the years ended December 31 (dollars in thousands):


	2023		2022			2021
Avista Utilities
Revenue from contracts with customers	$	1,485,510	$	1,400,027		$	1,233,904
Derivative revenues		199,133		286,309			152,590
Alternative revenue programs		4,899		(33,357	)		(6,635	)
Deferrals and amortizations for rate refunds to customers		1,026		207			2,984
Other utility revenues		12,289		10,629			10,156
Total Avista Utilities		1,702,857		1,663,815			1,392,999
AEL&P
Revenue from contracts with customers		47,525		45,703			45,051
Deferrals and amortizations for rate refunds to customers		—		(614	)		(190	)
Other utility revenues		614		615			505
Total AEL&P		48,139		45,704			45,366
Other
Revenue from contracts with customers		—		—			2
Other revenues		558		688			569
Total Other		558		688			571
Total operating revenues	$	1,751,554	$	1,710,207		$	1,438,936

Utility Revenue from Contracts with Customers by Type and Service

The following table disaggregates revenue from contracts with customers associated with the Company's electric operations for the years ended December 31 (dollars in thousands):


	2023						2022						2021
	Avista Utilities		AEL&P		Total Utility		Avista Utilities		AEL&P		Total Utility		Avista Utilities		AEL&P		Total Utility
ELECTRIC OPERATIONS
Revenue from contracts with customers
Residential	$	425,258	$	20,232	$	445,490	$	414,823	$	19,667	$	434,490	$	394,717	$	18,940	$	413,657
Commercial and governmental		343,523		27,026		370,549		338,656		25,782		364,438		326,173		25,861		352,034
Industrial		109,689		—		109,689		107,740		—		107,740		106,756		—		106,756
Public street and highway lighting		7,976		267		8,243		7,483		254		7,737		7,472		250		7,722
Total retail revenue		886,446		47,525		933,971		868,702		45,703		914,405		835,118		45,051		880,169
Transmission		32,941		—		32,941		32,307		—		32,307		21,005		—		21,005
Other revenue from contracts with customers		45,332		—		45,332		49,920		—		49,920		33,870		—		33,870
Total revenue from contracts with customers	$	964,719	$	47,525	$	1,012,244	$	950,929	$	45,703	$	996,632	$	889,993	$	45,051	$	935,044

The following table disaggregates revenue from contracts with customers associated with the Company's natural gas operations for the years ended December 31 (dollars in thousands):


	2023		2022		2021
	Avista Utilities		Avista Utilities		Avista Utilities
NATURAL GAS OPERATIONS
Revenue from contracts with customers
Residential	$	325,631	$	284,452	$	221,405
Commercial		164,048		139,923		100,819
Industrial and interruptible		17,315		10,471		7,796
Total retail revenue		506,994		434,846		330,020
Transportation		8,172		8,627		8,547
Other revenue from contracts with customers		5,625		5,625		5,344
Total revenue from contracts with customers	$	520,791	$	449,098	$	343,911

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-9

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-10

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-15

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-12

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-13

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org//606/tableOfContent

Investments, Debt and Equity Securities [Abstract]

Equity Investments

12 Months Ended

Dec. 31, 2023

Equity Investments

NOTE 7. EQUITY INVESTMENTS

The Company has equity investment holdings that are accounted for under the equity method, at fair value, or using the fair value measurement alternative provided for in ASC 321, adjusting cost for impairment and observable price changes.


	2023		2022
Equity method investments	$	78,513	$	70,196
Investments without readily determinable fair value
Non-recurring fair value		24,583		23,329
Recurring fair value		50,254		54,284
Total	$	153,350	$	147,809

Equity Method Investments

The Company has investments in limited partnerships (or the functional equivalent) where Avista Corp. is a limited partner investor in an investment fund. Holdings in these investment funds are accounted for under the equity method. Underlying investments held by the funds are recorded at fair value by the fund, and Avista Corp. recognizes its share of the fund's profits and losses based on its ownership percentage.

The Company also has ownership in joint ventures with underlying holdings in real estate, which are accounted for under the equity method.

The Company's earnings and losses related to equity method investments are included in “Other income- net” on the Consolidated Statements of Net Income.

Investments Without Readily Determinable Fair Value

The Company has investments that do not qualify for equity method treatment, and for which fair value is not readily determinable. The Company has elected the measurement alternative for a majority of these investments, adjusting the recorded value on a non-recurring basis as a result of observable transactions involving the underlying asset. The observable transaction indicates an updated fair value, and the Company adjusts carrying value to fair value at this point in time. The fair value of these assets is determined using the market approach, and these assets are considered level 2 on the fair value hierarchy (see Note 18 for a description of the fair value hierarchy).

The Company has elected to record two investments at fair value on a recurring basis. These equity investments are considered Level 3 on the fair value hierarchy. See further discussion of Level 3 equity investments, including valuation methods and significant inputs, as included in Note 18.

Realized and unrealized gains or losses in equity investments are included in net income. The following table summarizes net unrealized gains (losses) related to investments without readily determinable fair value held as of the end of the respective period for the years ended December 31 (dollars in thousands):


	2023			2022		2021
Investments recorded at non-recurring fair value	$	—		$	12,285	$	8,761
Investments recorded at recurring fair value		(4,323	)		33,382		—
Total	$	(4,323	)	$	45,667	$	8,761

Net unrealized gains recorded related to investments recorded at non-recurring fair value result from identified observable transactions. On a cumulative basis, the Company has recognized a net gain of $14.8 million for fair value adjustments to investments recorded at non-recurring fair value held at December 31, 2023.

Accumulated Other Comprehensive Loss

12 Months Ended

Dec. 31, 2023

Accumulated Other Comprehensive Loss [Abstract]

Accumulated Other Comprehensive Loss

NOTE 20. ACCUMULATED OTHER COMPREHENSIVE LOSS

Accumulated Other Comprehensive Loss

Accumulated other comprehensive loss, net of tax, consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $95 and $547, respectively	$	357	$	2,058

The following table details the reclassifications out of accumulated other comprehensive loss by component for the years ended December 31 (dollars in thousands):


	Amounts Reclassified from Accumulated Other Comprehensive Loss
Details about Accumulated Other Comprehensive Loss Components (Affected Line Item in Statements of Income)	2023			2022			2021
Amortization of defined benefit pension and postretirement benefit items
Amortization of net prior service cost (a)	$	(558	)	$	(4,095	)	$	(793	)
Amortization of net loss (a)		18,872			57,650			38,070
Adjustment due to effects of regulation (a)		(16,161	)		(42,187	)		(33,050	)
Total before tax (b)		2,153			11,368			4,227
Tax expense (b)		(452	)		(2,387	)		(888	)
Net of tax (b)	$	1,701		$	8,981		$	3,339

(a)

These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 12 for additional details).

(b)

Description is also the affected line item on the Consolidated Statements of Income.

Equity Investments - Summary of Equity Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Equity Investments [Line items]
Equity method investments	$ 78,513	$ 70,196
Total	153,350	147,809
Non-recurring Fair Value [Member]
Equity Investments [Line items]
Investments without readily determinable fair value	24,583	23,329
Recurring Fair Value [Member]
Equity Investments [Line items]
Investments without readily determinable fair value	$ 50,254	$ 54,284

Short-Term Borrowings

12 Months Ended

Dec. 31, 2023

Short-Term Debt [Abstract]

Short-Term Borrowings

NOTE 15. SHORT-TERM BORROWINGS

Avista Corp.

Lines of Credit

Avista Corp. has a committed line of credit in the total amount of $500.0 million. with expiration date of June 2028. The Company has the option to extend for two additional one year periods (subject to customary conditions). In June 2023, the then-existing agreement was amended to increase the capacity of the committed line of credit from $400.0 million to $500.0 million, extend the expiration date, and replace the London Interbank Offered Rate (LIBOR) provisions with Secured Overnight Financing Rate (SOFR) provisions. The committed line of credit is secured by non-transferable first mortgage bonds of the Company issued to the agent bank that would only become due and payable in the event, and then only to the extent, that the Company defaults on its obligations under the committed line of credit.

Balances outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed line of credit were as follows as of December 31 (dollars in thousands):


	2023			2022
Balance outstanding at end of period	$	349,000		$	313,000
Letters of credit outstanding at end of period		4,700			35,563
Average interest rate at end of period		6.46	%		5.31	%

In December 2022, Avista Corp. entered into an additional revolving credit agreement in the amount of $100.0 million. As of December 31, 2022, the Company did not have any outstanding borrowings under this agreement. The agreement was terminated in June 2023.

As of December 31, 2023 and 2022, the borrowings outstanding under Avista Corp.'s committed lines of credit were classified as short-term borrowings on the Consolidated Balance Sheets.

2022 Term Loan

In December 2022, the Company entered into a term loan agreement in the amount of $150.0 million with a maturity date of March 30, 2023. The Company borrowed the entire $150.0 million available under the agreement in 2022 and repaid the entire outstanding balance in March 2023. The borrowings outstanding under this agreement were classified as short-term borrowings on the Consolidated Balance Sheets.

2022 Letter of Credit Facility

In December 2022, the Company entered into a continuing letter of credit agreement in the aggregate amount of $50.0 million. Either party may terminate the agreement at any time.

The Company had $20.0 million and $18.5 million in letters of credit outstanding under this agreement as of December 31, 2023 and December 31, 2022, respectively. Letters of credit are not reflected on the Consolidated Balance Sheets. If a letter of credit were drawn upon by the holder, we would have an immediate obligation to reimburse the bank that issued that letter.

Covenants and Default Provisions

The short-term borrowing agreements contain customary covenants and default provisions, including a change in control (as defined in the agreements). The events of default under each of the credit facilities also include a cross default from other indebtedness (as defined) and in some cases other obligations. Most of the short-term borrowing agreement also include a covenant which does not permit the ratio of “consolidated total debt” to “consolidated total capitalization” of Avista Corp. to be greater than 65 percent at any time. As of December 31, 2023, the Company complied with this covenant.

AEL&P

AEL&P has a committed line of credit in the amount of $25.0 million that expires in June 2028. The committed line of credit is secured by non-transferable first mortgage bonds of AEL&P issued to the agent bank that would only become due and payable in the event, and then only to the extent, that AEL&P defaults on its obligations under the committed line of credit.

The committed line of credit agreement contains customary covenants and default provisions. The credit agreement has a covenant which does not permit the ratio of “consolidated total debt at AEL&P” to “consolidated total capitalization at AEL&P,” including the impact of the Snettisham bonds to be greater than 67.5 percent at any time. As of December 31, 2023, AEL&P complied with this covenant.

As of December 31, 2023, and 2022 there were no borrowings under the AEL&P committed line of credit.

Regulatory Matters - Schedule of Regulatory Assets and Liabilities (Parenthetical) (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018	Dec. 31, 2017
Regulated Asset Liability [Line Items]
Federal statutory tax rate	21.00%	21.00%	21.00%	21.00%	35.00%
Avista Utilities [Member]
Regulated Asset Liability [Line Items]
Tax cuts and jobs act period to return plant related excess deferred income taxes	33 years
Alaska Electric Light & Power [Member]
Regulated Asset Liability [Line Items]
Tax cuts and jobs act period to return plant related excess deferred income taxes	22 years

Common Stock - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Preferred stock, shares outstanding	0	0
Amount available for dividend distribution without affecting covenants	$ 295,600
Preferred stock, shares authorized	10,000,000
Proceeds from issuance of common stock	$ 112,308	$ 137,778	$ 89,998
Common stock, shares authorized	200,000,000	200,000,000
Common Stock [Member]
Class Of Stock [Line Items]
Shares issued through sales agency agreements	2,999,246	3,310,488	2,150,336
Issuance of common stock through sales agency agreements, net of issuance costs	$ 111,848	$ 137,173	$ 88,457
Avista Utilities [Member]
Class Of Stock [Line Items]
Regulatory restrictions, maximum debt to equity	35.00%

Derivatives and Risk Management - Schedule of Collateral Outstanding Related to Derivative Instruments (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Balance sheet offsetting (cash collateral against net derivative positions)	$ 42,355,000	$ 105,439,000
Commodity Contracts [Member]
Derivative [Line Items]
Cash collateral posted	43,095,000	171,581,000
Letters of credit outstanding	20,000,000	49,425,000
Balance sheet offsetting (cash collateral against net derivative positions)	42,355,000	105,439,000
Liabilities with credit-risk-related contingent features	18,016,000
Additional collateral to post	15,125,000
Interest Rate Swap [Member]
Derivative [Line Items]
Letters of credit outstanding	0	$ 0
Liabilities with credit-risk-related contingent features	182,000
Additional collateral to post	$ 182,000

Regulatory Matters - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Regulated Asset Liability [Line Items]
Earning a return, asset	$ 543,185
Not earning a return, asset	480,348
Pending regulatory treatment, asset	16,962
Regulatory assets	146,327	$ 193,787
Non-current regulatory assets	894,168	833,328
Earning a return, liability	816,631
Not earning a return, liability	94,342
Pending Regulatory Treatment Liability	21,700
Regulatory liabilities	76,007	95,665
Non-current regulatory liabilities	856,666	840,837
Deferred natural gas costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	9,296
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	9,296	0
Non-current regulatory liabilities	0	0
Deferred Power Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	4,000
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	0	0
Non-current regulatory liabilities	4,000	0
Utility Plant Retirement Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	417,027
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	0	0
Non-current regulatory liabilities	417,027	376,817
Excess Deferred Income Taxes [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	307,539
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	14,510	15,310
Non-current regulatory liabilities	293,029	314,096
Other Income Tax Related Liabilities [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	81,711
Pending Regulatory Treatment Liability	0
Regulatory liabilities	25,129	57,957
Non-current regulatory liabilities	56,582	76,638
Climate Commitment Act [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	37,231
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	0	0
Non-current regulatory liabilities	37,231	0
Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	12,216
Not earning a return, liability	0
Pending Regulatory Treatment Liability	11,536
Regulatory liabilities	0	0
Non-current regulatory liabilities	$ 23,752	24,204
Decoupling Rebates [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory liability	2 years
Earning a return, liability	$ 25,024
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	18,680	9,469
Non-current regulatory liabilities	6,344	20,476
COVID-19 Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	8
Pending Regulatory Treatment Liability	10,164
Regulatory liabilities	0	0
Non-current regulatory liabilities	10,172	11,874
Other Regulatory Liabilities [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	4,298
Not earning a return, liability	12,623
Pending Regulatory Treatment Liability	0
Regulatory liabilities	8,392	12,929
Non-current regulatory liabilities	8,529	16,732
Deferred Income Tax [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	244,303
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	244,303	$ 240,325
Pension and Other Postretirement Benefit Plans [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets		12 years
Earning a return, asset	0
Not earning a return, asset	117,658
Pending regulatory treatment, asset	0
Regulatory assets	0	$ 0
Non-current regulatory assets	117,658	135,337
Climate Commitment Act [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	46,022
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	46,022	0
Energy Commodity Derivatives [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	69,139
Pending regulatory treatment, asset	0
Regulatory assets	51,419	112,090
Non-current regulatory assets	17,720	18,185
Unamortized Debt Repurchase Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	5,701
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	$ 5,701	6,177
Settlement with Coeur d'Alene Tribe [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	36 years
Earning a return, asset	$ 36,692
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	36,692	37,809
Demand Side Management Programs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	10,033
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	$ 10,033	3,683
Decoupling Surcharge [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	2 years
Earning a return, asset	$ 10,107
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	4,638	6,250
Non-current regulatory assets	5,469	5,449
Utility Plant Abandoned [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	34,852
Not earning a return, asset	3,422
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	38,274	24,389
Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	178,898
Not earning a return, asset	0
Pending regulatory treatment, asset	591
Regulatory assets	0	0
Non-current regulatory assets	179,489	185,919
Deferred power costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	49,844
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	29,190	23,356
Non-current regulatory assets	20,654	24,043
Deferred Natural Gas Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	60,667
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	60,667	52,091
Non-current regulatory assets	0	0
AFUDC Above FERC Allowed Rate [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	49,985
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	49,985	51,649
COVID-19 Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	0
Pending regulatory treatment, asset	12,142
Regulatory assets	0	0
Non-current regulatory assets	12,142	9,793
Advanced Meter Infrastructure [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	29,345
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	29,345	32,381
Other Regulatory Assets [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	41,072
Not earning a return, asset	35,793
Pending regulatory treatment, asset	4,229
Regulatory assets	413	0
Non-current regulatory assets	$ 80,681	$ 58,189

Regulatory Matters - Summary of Energy Recovery Mechanism (Details)	Dec. 31, 2023
Annual Power Supply Cost Variability Within 0 to 4 Mllion [Member]
Public Utilities, General Disclosures [Line Items]
Percentage of Deferred for Future Surcharge or Rebate to Customers	0.00%
Expense or Benefit to the Company	100.00%
Annual Power Supply Cost Variability Higher by 4 Million to 10 Million [Member]
Public Utilities, General Disclosures [Line Items]
Percentage of Deferred for Future Surcharge or Rebate to Customers	50.00%
Expense or Benefit to the Company	50.00%
Annual Power Supply Cost Variability Lower by 4 Million to 10 Million [Member]
Public Utilities, General Disclosures [Line Items]
Percentage of Deferred for Future Surcharge or Rebate to Customers	75.00%
Expense or Benefit to the Company	25.00%
Annual Power Supply Cost Variability Higher by Over 10 Million [Member]
Public Utilities, General Disclosures [Line Items]
Percentage of Deferred for Future Surcharge or Rebate to Customers	90.00%
Expense or Benefit to the Company	10.00%

Accumulated Other Comprehensive Loss (Tables)

12 Months Ended

Dec. 31, 2023

Accumulated Other Comprehensive Loss [Abstract]

Schedule of Accumulated Other Comprehensive Loss, Net of Tax

Accumulated other comprehensive loss, net of tax, consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $95 and $547, respectively	$	357	$	2,058

Reclassification out of Accumulated Other Comprehensive Loss

The following table details the reclassifications out of accumulated other comprehensive loss by component for the years ended December 31 (dollars in thousands):


	Amounts Reclassified from Accumulated Other Comprehensive Loss
Details about Accumulated Other Comprehensive Loss Components (Affected Line Item in Statements of Income)	2023			2022			2021
Amortization of defined benefit pension and postretirement benefit items
Amortization of net prior service cost (a)	$	(558	)	$	(4,095	)	$	(793	)
Amortization of net loss (a)		18,872			57,650			38,070
Adjustment due to effects of regulation (a)		(16,161	)		(42,187	)		(33,050	)
Total before tax (b)		2,153			11,368			4,227
Tax expense (b)		(452	)		(2,387	)		(888	)
Net of tax (b)	$	1,701		$	8,981		$	3,339

(a)

These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 12 for additional details).

(b)

Description is also the affected line item on the Consolidated Statements of Income.

Property, Plant And Equipment (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Net Utility Property

Net utility property consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Utility plant in service	$	7,799,481	$	7,561,688
Construction work in progress		179,527		164,147
Total		7,979,008		7,725,835
Less: Accumulated depreciation and amortization		2,278,952		2,281,126
Total net utility property	$	5,700,056	$	5,444,709

Summary of Ratio of Depreciation to Average Depreciable Property and Average Service Lives for Utility Plan in Service

For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31:


	2023			2022			2021
Avista Utilities		3.52	%		3.50	%		3.54	%
Alaska Electric Light and Power Company		2.78	%		2.78	%		2.77	%

The average service lives for the following broad categories of utility plant in service are (in years):


	Avista Utilities		Alaska Electric Light and Power Company
Electric thermal/other production		26		41
Hydroelectric production		79		42
Electric transmission		50		43
Electric distribution		40		39
Natural gas distribution property		44	N/A
Other shorter-lived general plant		8		18

The gross balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in thousands):


	2023		2022
Avista Utilities:
Electric production	$	1,498,398	$	1,593,795
Electric transmission		1,059,389		994,709
Electric distribution		2,383,201		2,236,376
Electric construction work-in-progress (CWIP) and other		394,711		376,981
Electric total		5,335,699		5,201,861
Natural gas underground storage		59,994		58,072
Natural gas distribution		1,539,467		1,452,637
Natural gas CWIP and other		91,492		88,264
Natural gas total		1,690,953		1,598,973
Common plant (including CWIP)		759,498		744,173
Total Avista Utilities		7,786,150		7,545,007
AEL&P:
Electric production		118,817		106,390
Electric transmission		22,827		22,856
Electric distribution		32,322		29,269
Electric CWIP and other		8,552		12,295
Electric total		182,518		170,810
Common plant		10,340		10,018
Total AEL&P		192,858		180,828
Total gross utility property		7,979,008		7,725,835
Other (1)		6,425		16,631
Total	$	7,985,433	$	7,742,466

(1)

Included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets. Accumulated depreciation was less than $0.1 million as of December 31, 2023 and $2.4 million as of December 31, 2022 for the other businesses.

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Schedule of Inventory

Inventories of materials and supplies, emissions allowances, stored natural gas and fuel stock are recorded at average cost and consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Materials and supplies	$	81,651	$	75,766
Emission allowances		56,097		—
Stored natural gas		16,272		26,788
Fuel stock		5,964		5,120
Total	$	159,984	$	107,674

Schedule of Other Current Assets

Other current assets consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$	—	$	66,142
Prepayments		52,752		30,201
Income taxes receivable		29,234		30,740
Derivative assets net of collateral		11,821		18,198
Other		9,977		5,886
Total	$	103,784	$	151,167

Other Property and Investments-Net and Other Non-Current Assets

Other property and investments-net and other non-current assets consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Equity investments	$	153,350	$	147,809
Operating lease ROU assets		67,585		68,238
Finance lease ROU assets		36,414		40,056
Non-utility property		33,813		25,401
Notes receivable		15,287		17,954
Long-term prepaid license fees		19,448		17,936
Pension assets		32,997		13,382
Investment in affiliated trust		11,547		11,547
Deferred compensation assets		7,794		7,541
Other		15,750		15,221
Total	$	393,985	$	365,085

Other Current Liabilities

Other current liabilities consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Accrued taxes other than income taxes	$	31,928	$	38,568
Employee paid time off accruals		32,072		29,279
Accrued interest		23,539		20,863
Pensions and other postretirement benefits		14,082		15,625
Derivative liabilities		17,217		26,910
Climate Commitment Act obligations		19,081		—
Deferred wholesale revenue		—		8,481
Other		54,017		49,689
Total	$	191,936	$	189,415

Schedule of Other Non-Current Liabilities and Deferred Credits

Other non-current liabilities and deferred credits consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Operating lease liabilities	$	63,559	$	64,284
Finance lease liabilities		39,095		42,495
Deferred investment tax credits		28,233		28,784
Climate Commitment Act obligations		26,026		—
Asset retirement obligations		18,058		15,783
Derivative liabilities		17,902		7,892
Other		17,357		16,617
Total	$	210,230	$	175,855

Pension Plans and Other Postretirement Benefit Plans - Schedule of Expected Benefit Payments (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
2024	$ 41,562
2025	42,123
2026	42,941
2027	43,517
2028	44,700
Total 2029- 2033	232,345
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2024	7,084
2025	7,266
2026	7,436
2027	7,608
2028	7,822
Total 2029- 2033	$ 40,805

Fair Value (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Schedule of Carrying Value and Estimated Fair Value of Financial Instruments


	2023				2022
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Long-term debt (Level 2)	$	1,100,000	$	968,893	$	1,113,500	$	966,881
Long-term debt (Level 3)		1,450,000		1,166,512		1,200,000		881,480
Snettisham finance lease obligation (Level 3)		42,495		39,600		45,730		41,700
Long-term debt to affiliated trusts (Level 3)		51,547		46,098		51,547		42,836

Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis


	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2023
Assets:
Energy commodity derivatives (2)	$	—	$	30,954	$	—	$	(22,802	)	$	8,152
Foreign currency exchange derivatives		—		2		—		—			2
Interest rate swap derivatives		—		3,667		—		—			3,667
Equity investments (3)		—		—		50,254		—			50,254
Deferred compensation assets:
Mutual Funds:
Fixed income securities (3)		1,117		—		—		—			1,117
Equity securities (3)		6,524		—		—		—			6,524
Total	$	7,641	$	34,623	$	50,254	$	(22,802	)	$	69,716
Liabilities:
Energy commodity derivatives (2)	$	—	$	91,844	$	8,250	$	(65,157	)	$	34,937
Interest rate swap derivatives		—		182		—		—			182
Total	$	—	$	92,026	$	8,250	$	(65,157	)	$	35,119

The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Consolidated Balance Sheets as of December 31, 2022 at fair value on a recurring basis (dollars in thousands):


	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2022
Assets:
Energy commodity derivatives (2)	$	—	$	146,232	$	288	$	(136,605	)	$	9,915
Foreign currency exchange derivatives		—		43		—		—			43
Interest rate swap derivatives		—		11,184		—		—			11,184
Equity investments (3)		—		—		54,284		—			54,284
Deferred compensation assets:
Mutual Funds:
Fixed income securities (3)		1,267		—		—		—			1,267
Equity securities (3)		6,132		—		—		—			6,132
Total	$	7,399	$	157,459	$	54,572	$	(136,605	)	$	82,825
Liabilities:
Energy commodity derivatives (2)	$	—	$	258,769	$	18,022	$	(242,044	)	$	34,747
Foreign currency exchange derivatives		—		3		—		—			3
Interest rate swap derivatives		—		52		—		—			52
Total	$	—	$	258,824	$	18,022	$	(242,044	)	$	34,802

(1)

(2)

The Level 3 energy commodity derivative balances are associated with natural gas exchange agreements.

(3)

These assets are included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets.

Schedule of Quantitative Information

The following table presents the quantitative information which was used to estimate the fair values of the Level 3 assets and liabilities above as of December 31, 2023 (dollars in thousands):


	Fair Value (Net) at
	December 31, 2023			Valuation Technique	Unobservable Input	Range
Natural gas exchange	$	(8,250	)	Internally derived weighted average cost of gas	Forward purchase prices	$1.64 - $3.07/mmBTU $2.40 Weighted Average
					Forward sales prices	$2.13 - $8.99/mmBTU $5.45 Weighted Average
					Purchase volumes	300,000 - 310,000 mmBTUs
					Sales volumes	75,000 - 310,000 mmBTUs


	Fair Value at
	December 31, 2023		Valuation Technique	Unobservable Input	Range
Equity investments	$	50,254	Market approach	Comparable enterprise values	$130,000-$388,600 $246,000 Average
				Time to liquidity event	1.5 years
			Discounted cash flows	Revenue market multiples	0.45x to 5.69x Revenue 1.89x Average
				Market exit reduction	50%
				Discount rate	25%
				Annual revenues	$15,000-$245,000
				Terminal date	2027

Schedule of Activity For Energy Commodity Derivative Assets (Liabilities) Measured At Fair Value Using Significant Unobservable Inputs (Level 3)

The following table presents activity for assets and liabilities measured at fair value using significant unobservable inputs (Level 3) for the years ended December 31 (dollars in thousands):


	Natural Gas Exchange Agreement (1)			Equity Investments			Total
Year ended December 31, 2023:
Balance as of January 1, 2023	$	(17,734	)	$	54,284		$	36,550
Total gains or (losses) (realized/unrealized):
Included in regulatory assets		9,238			—			9,238
Recognized in net income		—			(4,323	)		(4,323	)
Purchases and debt conversions		—			3,293			3,293
Settlements		246			—			246
Other		—			(3,000	)		(3,000	)
Ending balance as of December 31, 2023	$	(8,250	)	$	50,254		$	42,004
Year ended December 31, 2022:
Balance as of January 1, 2022	$	(7,771	)	$	—		$	(7,771	)
Transfers in (2)		—			20,902			20,902
Total gains or (losses) (realized/unrealized):
Included in regulatory assets		(4,740	)		—			(4,740	)
Recognized in net income		—			33,382			33,382
Settlements		(5,223	)		—			(5,223	)
Ending balance as of December 31, 2022	$	(17,734	)	$	54,284		$	36,550
Year ended December 31, 2021:
Balance as of January 1, 2021	$	(8,410	)	$	—		$	(8,410	)
Total gains (realized/unrealized):
Included in regulatory assets		4,292			—			4,292
Settlements		(3,653	)		—			(3,653	)
Ending balance as of December 31, 2021	$	(7,771	)	$	—		$	(7,771	)

(1)

There were no purchases, issuances or transfers from other categories of derivatives instruments during the periods presented in the table above.

(2)

The Company elected to account for certain equity investments at recurring fair value in 2022, as such the transfer in represents the value as of the election. See further discussion within Note 7.

Long-Term Debt

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Long-Term Debt

NOTE 16. LONG-TERM DEBT

The following details long-term debt outstanding as of December 31 (dollars in thousands):


Maturity Year	Description	Interest Rate	2023			2022
Avista Corp. Secured Long-Term Debt
2023	Secured Medium-Term Notes	7.18%-7.54%		—			13,500
2028	Secured Medium-Term Notes	6.37%		25,000			25,000
2032	Secured Pollution Control Bonds (1)	(1)		66,700			66,700
2034	Secured Pollution Control Bonds (1)	(1)		17,000			17,000
2035	First Mortgage Bonds	6.25%		150,000			150,000
2037	First Mortgage Bonds	5.70%		150,000			150,000
2040	First Mortgage Bonds	5.55%		35,000			35,000
2041	First Mortgage Bonds	4.45%		85,000			85,000
2044	First Mortgage Bonds	4.11%		60,000			60,000
2045	First Mortgage Bonds	4.37%		100,000			100,000
2047	First Mortgage Bonds	4.23%		80,000			80,000
2047	First Mortgage Bonds	3.91%		90,000			90,000
2048	First Mortgage Bonds	4.35%		375,000			375,000
2049	First Mortgage Bonds	3.43%		180,000			180,000
2050	First Mortgage Bonds	3.07%		165,000			165,000
2051	First Mortgage Bonds	3.54%		175,000			175,000
2051	First Mortgage Bonds	2.90%		140,000			140,000
2052	First Mortgage Bonds	4.00%		400,000			400,000
2053	First Mortgage Bonds (2)	5.66%		250,000			—
	Total Avista Corp. secured long-term debt			2,543,700			2,307,200
Alaska Electric Light and Power Company Secured Long-Term Debt
2044	First Mortgage Bonds	4.54%		75,000			75,000
	Total secured long-term debt			2,618,700			2,382,200
Alaska Energy and Resources Company Unsecured Long-Term Debt
2024	Unsecured Term Loan	3.44%		15,000			15,000
	Total secured and unsecured long-term debt			2,633,700			2,397,200
Other Long-Term Debt Components
	Unamortized debt discount			(689	)		(726	)
	Unamortized long-term debt issuance costs			(18,953	)		(18,261	)
	Total			2,614,058			2,378,213
	Secured Pollution Control Bonds held by Avista Corporation (1)			(83,700	)		(83,700	)
	Current portion of long-term debt			(15,000	)		(13,500	)
	Total long-term debt		$	2,515,358		$	2,281,013

(1)

In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new variable rate bond issues. The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company can remarket these bonds to unaffiliated investors at a later date, subject to market conditions. So long as Avista Corp. is the holder of these bonds, the bonds are not reflected as an asset or a liability on the Consolidated Balance Sheets.

(2)

In March 2023, the Company issued and sold $250.0 million of 5.66 percent first mortgage bonds due in 2053 with institutional investors in the private placement market. A portion of the net proceeds from the sale of these bonds was used for the construction or improvement of utility facilities, and a portion was used to refinance existing indebtedness, including the repayment of Avista Corp.'s $150.0 million term loan. In connection with the pricing of the first mortgage bonds in March 2023, the Company cash settled four interest rate swap derivatives (notional

aggregate amount of $40.0 million) and received a net amount of $7.5 million. See Note 8 for a discussion of interest rate swap derivatives.

The following table details future long-term debt maturities including long-term debt to affiliated trusts (see Note 17) (dollars in thousands):


	2024		2025		2026		2027		2028		Thereafter		Total
Debt maturities	$	15,000	$	—	$	—	$	—	$	25,000	$	2,561,547	$	2,601,547

Substantially all of Avista Utilities' and AEL&P's owned properties are subject to the lien of their respective mortgage indentures. Under the Mortgages and Deeds of Trust (Mortgages) securing their first mortgage bonds (including secured medium-term notes), Avista Utilities and AEL&P may each issue additional first mortgage bonds under their specific mortgage in an aggregate principal amount equal to the sum of:

•

66-2/3 percent of the cost or fair value to the Company (whichever is lower) of property additions of that entity which have not previously been made the basis of any application under that entity's Mortgage, or

•

an equal principal amount of retired first mortgage bonds of that entity which have not previously been made the basis of any application under that entity's Mortgage, or

•

deposit of cash.

Avista Utilities and AEL&P may not individually issue any additional first mortgage bonds (with certain exceptions in the case of bonds issued on the basis of retired bonds) unless the particular entity issuing the bonds has “net earnings” (as defined in that entity's Mortgage) for any period of 12 consecutive calendar months out of the preceding 18 calendar months that were at least twice the annual interest requirements on all mortgage securities at the time outstanding, including the first mortgage bonds to be issued, and on all indebtedness of prior rank. As of December 31, 2023, property additions and retired bonds would have allowed, and the net earnings test would not have prohibited, the issuance of $1.2 billion in an aggregate principal amount of additional first mortgage bonds at Avista Utilities and $51.4 million by AEL&P, at an assumed interest rate of 8 percent in each case.

Equity Investments - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) Investment
Equity Investments [Line items]
Gains on equity investments without readily determinable fair value, cumulative amount \| $	$ 14.8
Recurring fair value [Member]
Equity Investments [Line items]
Number of recurring fair value equity investments \| Investment	2

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2023

Long-Term Debt, Unclassified [Abstract]

Schedule of Long-term Debt Instruments


Maturity Year	Description	Interest Rate	2023			2022
Avista Corp. Secured Long-Term Debt
2023	Secured Medium-Term Notes	7.18%-7.54%		—			13,500
2028	Secured Medium-Term Notes	6.37%		25,000			25,000
2032	Secured Pollution Control Bonds (1)	(1)		66,700			66,700
2034	Secured Pollution Control Bonds (1)	(1)		17,000			17,000
2035	First Mortgage Bonds	6.25%		150,000			150,000
2037	First Mortgage Bonds	5.70%		150,000			150,000
2040	First Mortgage Bonds	5.55%		35,000			35,000
2041	First Mortgage Bonds	4.45%		85,000			85,000
2044	First Mortgage Bonds	4.11%		60,000			60,000
2045	First Mortgage Bonds	4.37%		100,000			100,000
2047	First Mortgage Bonds	4.23%		80,000			80,000
2047	First Mortgage Bonds	3.91%		90,000			90,000
2048	First Mortgage Bonds	4.35%		375,000			375,000
2049	First Mortgage Bonds	3.43%		180,000			180,000
2050	First Mortgage Bonds	3.07%		165,000			165,000
2051	First Mortgage Bonds	3.54%		175,000			175,000
2051	First Mortgage Bonds	2.90%		140,000			140,000
2052	First Mortgage Bonds	4.00%		400,000			400,000
2053	First Mortgage Bonds (2)	5.66%		250,000			—
	Total Avista Corp. secured long-term debt			2,543,700			2,307,200
Alaska Electric Light and Power Company Secured Long-Term Debt
2044	First Mortgage Bonds	4.54%		75,000			75,000
	Total secured long-term debt			2,618,700			2,382,200
Alaska Energy and Resources Company Unsecured Long-Term Debt
2024	Unsecured Term Loan	3.44%		15,000			15,000
	Total secured and unsecured long-term debt			2,633,700			2,397,200
Other Long-Term Debt Components
	Unamortized debt discount			(689	)		(726	)
	Unamortized long-term debt issuance costs			(18,953	)		(18,261	)
	Total			2,614,058			2,378,213
	Secured Pollution Control Bonds held by Avista Corporation (1)			(83,700	)		(83,700	)
	Current portion of long-term debt			(15,000	)		(13,500	)
	Total long-term debt		$	2,515,358		$	2,281,013

(1)

(2)

aggregate amount of $40.0 million) and received a net amount of $7.5 million. See Note 8 for a discussion of interest rate swap derivatives.

Schedule of Maturities of Long-term Debt


	2024		2025		2026		2027		2028		Thereafter		Total
Debt maturities	$	15,000	$	—	$	—	$	—	$	25,000	$	2,561,547	$	2,601,547

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

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Variable Interest Entities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	$ 7,702,477	$ 7,417,350	$ 6,853,583
VIE Commitments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	88,100
Limited Partnerships and Similar Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity Remaining Investment Commitment Amount	17,700
Equity Investment [Member] \| VIE Commitments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	78,500
Notes Receivable [Member] \| VIE Commitments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	$ 9,600
Minimum [Member] \| Limited Partnerships and Similar Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Restrictions on Withdrawal of Member Capital Account	2025
Maximum [Member] \| Limited Partnerships and Similar Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Restrictions on Withdrawal of Member Capital Account	2036
Variable Interest Entity, Not Primary Beneficiary [Member] \| Limited Partnerships and Similar Entities [Member] \| VIE Commitments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	$ 73,300

Energy Purchase Contracts (Schedule Of Utility Total Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Energy Purchase Contracts [Abstract]
Utility power resources	$ 607,155	$ 660,967	$ 431,199

Pension Plans and Other Postretirement Benefit Plans - Schedule of Fair Value Hierarchy of Other Postretirement Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 58,126	$ 49,472	$ 59,544

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

Stockholders' Equity Note [Abstract]

Common Stock

12 Months Ended

Dec. 31, 2023

Common Stock

NOTE 19. COMMON STOCK

The payment of dividends on common stock could be limited by:

•

certain covenants applicable to preferred stock (when outstanding) contained in the Company’s Restated Articles of Incorporation, as amended (currently there are no preferred shares outstanding),

•

certain covenants applicable to the Company's outstanding long-term debt and committed line of credit agreements,

•

the hydroelectric licensing requirements of section 10(d) of the FPA (see Note 1), and

•

certain requirements under the OPUC approval of the AERC acquisition in 2014. The OPUC's AERC acquisition order requires Avista Utilities to maintain a capital structure of no less than 35 percent common equity (inclusive of short-term debt). This limitation may be revised upon request by the Company with approval from the OPUC.

The requirements of the OPUC approval of the AERC acquisition are the most restrictive. Under the OPUC restriction, the amount available for dividends at December 31, 2023 was $295.6 million.

See the Consolidated Statements of Equity for dividends declared in the years 2021 through 2023.

The Company has 10 million authorized shares of preferred stock. The Company did not have preferred stock outstanding as of December 31, 2023 and 2022.

Common Stock Issuances

The Company issued common stock for total net proceeds of $112.3 million in 2023. Most of these issuances came through the Company's sales agency agreements under which the sales agents may offer and sell new shares of common stock from time to time. In 2023, 3.0 million shares were issued under these agreements resulting in total net proceeds of $111.8 million.

The entire disclosure for equity.

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-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

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-Name Accounting Standards Codification
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Long Term Debt To Affiliated Trust [Abstract]

Summary of Significant Accounting Policies - Estimated Retirement Costs Collected from Customers (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Regulated Asset Liability [Line Items]
Regulatory liability for utility plant retirement costs	$ 856,666	$ 840,837
Utility Plant Retirement Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory liability for utility plant retirement costs	$ 417,027	$ 376,817

Derivatives and Risk Management - Summary of Unsettled Interest Rate Swap Derivatives (Details) - Interest Rate Swap [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Contract	Dec. 31, 2022 USD ($) Contract
2023 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts \| Contract		4
Notional Amount \| $		$ 40,000
Mandatory Cash Settlement Date		2023
2024 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts \| Contract	2	1
Notional Amount \| $	$ 20,000	$ 10,000
Mandatory Cash Settlement Date	2024	2024
2025 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts \| Contract	1
Notional Amount \| $	$ 10,000
Mandatory Cash Settlement Date	2025

Derivatives and Risk Management - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) MMBTU MWh	Dec. 31, 2022 USD ($) MMBTU MWh
Canadian [Member]
Derivative [Line Items]
Number of days Canadian currency prices are settled with U.S. dollars	60 days
Interest Rate Swap [Member]
Derivative [Line Items]
Letters of credit outstanding \| $	$ 0	$ 0
Purchase [Member] \| Physical [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0	0
Purchase [Member] \| Physical [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0	0
Purchase [Member] \| Financial [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0	0
Purchase [Member] \| Financial [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0	0
Sales [Member] \| Physical [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0	0
Sales [Member] \| Physical [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0	0
Sales [Member] \| Financial [Member] \| Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MWh	0	0
Sales [Member] \| Financial [Member] \| Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years \| MMBTU	0	0

Jointly Owned Electric Facilities - Additional Information (Details)	Dec. 31, 2023
Jointly Owned Utility Plant, Net Ownership Amount [Abstract]
Owners percentage interest	15.00%

Regulatory Matters

12 Months Ended

Dec. 31, 2023

Regulated Operations [Abstract]

Regulatory Matters

NOTE 23. REGULATORY MATTERS

Regulatory Assets and Liabilities

The following table presents the Company’s regulatory assets and liabilities as of December 31, 2023 (dollars in thousands):


				Receiving Regulatory Treatment						2023				2022
	Remaining Amortization Period			(1) Earning A Return		Not Earning A Return		(2) Expected Recovery or Refund		Current		Non- current		Current		Non- current
Regulatory Assets:
Deferred income tax	(3) (16)			$	—	$	244,303	$	—	$	—	$	244,303	$	—	$	240,325
Pensions and other postretirement benefit plans		(4	)		—		117,658		—		—		117,658		—		135,337
Climate Commitment Act		(14	)		46,022		—		—		—		46,022		—		—
Energy commodity derivatives		(5	)		—		69,139		—		51,419		17,720		112,090		18,185
Unamortized debt repurchase costs		(6	)		5,701		—		—		—		5,701		—		6,177
Settlement with Coeur d’Alene Tribe	2059				36,692		—		—		—		36,692		—		37,809
Demand side management programs		(3	)		—		10,033		—		—		10,033		—		3,683
Decoupling surcharge	2025				10,107		—		—		4,638		5,469		6,250		5,449
Utility plant abandoned		(7	)		34,852		3,422		—		—		38,274		—		24,389
Interest rate swaps		(8	)		178,898		—		591		—		179,489		—		185,919
Deferred power costs		(3	)		49,844		—		—		29,190		20,654		23,356		24,043
Deferred natural gas costs		(3	)		60,667		—		—		60,667		—		52,091		—
AFUDC above FERC allowed rate		(11	)		49,985		—		—		—		49,985		—		51,649
COVID-19 deferrals		(12	)		—		—		12,142		—		12,142		—		9,793
Advanced meter infrastructure		(13	)		29,345		—		—		—		29,345		—		32,381
Other regulatory assets		(3	)		41,072		35,793		4,229		413		80,681		—		58,189
Total regulatory assets				$	543,185	$	480,348	$	16,962	$	146,327	$	894,168	$	193,787	$	833,328
Regulatory Liabilities:
Deferred natural gas costs		(3	)	$	9,296	$	—	$	—	$	9,296	$	—	$	—	$	—
Deferred power costs		(3	)	$	4,000	$	—	$	—	$	—	$	4,000	$	—	$	—
Utility plant retirement costs		(9	)		417,027		—		—		—		417,027		—		376,817
Excess deferred income taxes		(10	)		307,539		—		—		14,510		293,029		15,310		314,096
Other income tax related liabilities	(3) (15)				—		81,711		—		25,129		56,582		57,957		76,638
Climate Commitment Act		(14	)		37,231		—		—		—		37,231		—		—
Interest rate swaps		(8	)		12,216		—		11,536		—		23,752		—		24,204
Decoupling rebate	2025				25,024		—		—		18,680		6,344		9,469		20,476
COVID-19 deferrals		(12	)		—		8		10,164		—		10,172		—		11,874
Other regulatory liabilities		(3	)		4,298		12,623		—		8,392		8,529		12,929		16,732
Total regulatory liabilities				$	816,631	$	94,342	$	21,700	$	76,007	$	856,666	$	95,665	$	840,837

(1)

Earning a return includes either interest on the regulatory asset/liability or a return on the investment as a component of rate base at the allowed rate of return.

(2)

Expected recovery is pending regulatory treatment including regulatory assets and liabilities with prior regulatory precedence.

(3)

Remaining amortization period varies depending on timing of underlying transactions.

(4)

(5)

The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and losses result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho and periodic general rates cases. The resulting regulatory assets associated with energy commodity derivative instruments have been concluded to be probable of recovery through future rates.

(6)

(7)

(8)

(9)

This amount is dependent upon the cost of removal of underlying utility plant assets and the life of utility plant.

(10)

(11)

This amount is being amortized based on the underlying utility plant assets and the life of utility plant.

(12)

(13)

(14)

(15)

(16)

The majority of this balance represents flow-through income tax accounting differences and the related tax gross-up which have a corresponding deferred tax liability within Note 13.

Power Cost Deferrals and Recovery Mechanisms

Deferred power supply costs are recorded as a deferred charge or liability on the Consolidated Balance Sheets for future prudence review and recovery or rebate through retail rates. The power supply costs deferred include certain differences between actual net power supply costs incurred by Avista Utilities and the costs included in base retail rates. This difference in net power supply costs primarily results from changes in:

•

short-term wholesale market prices and sales and purchase volumes,

•

the level, availability and optimization of hydroelectric generation,

•

the level and availability of thermal generation (including changes in fuel prices),

•

retail loads, and

•

sales of surplus transmission capacity.

In Washington, the ERM allows Avista Utilities to periodically increase or decrease electric rates with WUTC approval to reflect changes in power supply costs. The ERM is an accounting method used to track certain differences between actual power supply costs, net of wholesale sales and sales of fuel, and the amount included in base retail rates for Washington customers. Under the ERM, the Company defers these differences (over the $4.0 million deadband and sharing bands) for future surcharge or rebate to customers.

The following is a summary of the ERM:


Annual Power Supply Cost Variability	Deferred for Future Surcharge or Rebate to Customers	Expense or Benefit to the Company
within +/- $0 to $4 million (deadband)	0%	100%
higher by $4 million to $10 million	50%	50%
lower by $4 million to $10 million	75%	25%
higher or lower by over $10 million	90%	10%

Total net deferred power costs under the ERM were assets of $37.6 million as of December 31, 2023 and $30.5 million as of December 31, 2022. The deferred power cost assets represent amounts due from customers, and deferred power cost liabilities represent amounts due to customers.

Pursuant to WUTC requirements, should the cumulative deferral balance exceed $30 million in the rebate or surcharge direction, the Company must make a filing with the WUTC to adjust customer rates to either return the balance to customers or recover the balance from customers. Avista Utilities makes an annual filing on, or before, April 1 of each year to provide the opportunity for the WUTC staff and other interested parties to review the prudence of, and audit, the ERM deferred power cost transactions for the prior calendar year. In June 2023, the Company received approval from the WUTC for a rate surcharge to customers over a two-year period, effective July 1, 2023.

In the 2024 Washington general rate case, the Company proposed changing the ERM so the entire mechanism would result in a 95 percent customer, 5 percent company sharing basis. This request is pending WUTC approval.

Avista Utilities has a PCA mechanism in Idaho allowing for the modification of electric rates on October 1 of each year with IPUC approval. Under the PCA mechanism, Avista Utilities defers 90 percent of the difference between certain actual net power supply expenses and the amount included in base retail rates for its Idaho customers. The October 1 rate adjustments recover or rebate power costs deferred during the preceding July-June twelve-month period. Total net power supply costs deferred under the PCA mechanism were assets of $7.6 million as of December 31, 2023 and $16.3 million as of December 31, 2022. Deferred power cost assets represent amounts due from customers and liabilities represent amounts due to customers.

Natural Gas Cost Deferrals and Recovery Mechanisms

Avista Utilities files a PGA in all three states it serves to adjust natural gas rates for: 1) estimated commodity and pipeline transportation costs to serve natural gas customers for the coming year, and 2) the difference between actual and estimated commodity and transportation costs for the prior year. In Oregon, the Company absorbs (cost or benefit) 10 percent of the difference between actual and projected natural gas costs included in base retail rates for supply that is not hedged. Total net deferred natural gas costs were an asset of $51.4 million as of December 31, 2023 and $52.1 million as of December 31, 2022. Asset balances represent amounts due from customers and liabilities represent amounts due to customers.

Decoupling and Earnings Sharing Mechanisms

Decoupling (also known as an FCA in Idaho) is a mechanism designed to sever the link between a utility's revenues and consumers' energy usage. In each of Avista Utilities' jurisdictions, Avista Utilities' electric and natural gas revenues are adjusted so as to be based on the number of customers in certain customer rate classes and assumed “normal” kilowatt hour and therm sales, rather than being based on actual kilowatt hour and therm sales. The difference between revenues based on the number of customers and “normal” sales and revenues based on actual usage is deferred and either surcharged or rebated to customers beginning in the following year. Only residential and certain commercial customer classes are included in decoupling mechanisms.

Washington Decoupling and Earnings Sharing

In Washington, the WUTC approved the Company's decoupling mechanisms for electric and natural gas through March 31, 2025. In the Company's 2024 Washington general rate cases, it requested the mechanisms be extended through December 2026. That request is pending before the WUTC.

Electric and natural gas decoupling surcharge rate adjustments to customers are limited to a 3 percent increase on an annual basis, with remaining surcharge balance carried forward for recovery in a future period. There is no limit on the level of rebate rate adjustments. New customers added after a test period are not decoupled until included in a future test period.

The decoupling mechanisms each include an after-the-fact earnings test. At the end of each calendar year, separate electric and natural gas earnings calculations are made for the calendar year just ended. These earnings tests reflect actual decoupled revenues, normalized power supply costs and other normalizing adjustments. Through the 2022 general rate cases, the Company modified its earnings test so that if the Company earns more than 0.5 percent higher than the ROR authorized by the WUTC in the multi-year rate plan, the Company would defer these excess revenues and later return them to customers.

Idaho FCA and Earnings Sharing Mechanisms

In Idaho, the IPUC approved the implementation of FCAs for electric and natural gas through March 31, 2025.

Oregon Decoupling Mechanism

In Oregon, the Company has a decoupling mechanism for natural gas. An earnings review is conducted on an annual basis. In the annual earnings review, if the Company earns more than 100 basis points above its allowed ROE, one-third of the earnings above the 100 basis points would be deferred and later returned to customers. The earnings review is separate from the decoupling mechanism and was in place prior to decoupling.

Cumulative Decoupling and Earnings Sharing Mechanism Balances


	December 31,			December 31,
	2023			2022
Washington
Decoupling rebate	$	(3,232	)	$	(13,210	)
Idaho
Decoupling rebate	$	(7,961	)	$	(7,889	)
Provision for earnings sharing rebate		(572	)		(686	)
Oregon
Decoupling (rebate) surcharge	$	(3,724	)	$	2,853

Long-Term Debt to Affiliated Trusts

12 Months Ended

Dec. 31, 2023

Long-Term Debt To Affiliated Trusts

NOTE 17. LONG-TERM DEBT TO AFFILIATED TRUSTS

In 1997, the Company issued Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B, with a principal amount of $51.5 million to Avista Capital II, an affiliated business trust formed by the Company. Avista Capital II issued $50.0 million of Preferred Trust Securities with a floating distribution rate of LIBOR plus 0.875 percent, calculated and reset quarterly. Effective on July 3, 2023, the reference to LIBOR in the formulation for the distribution rate on these securities was replaced, by operation of law, with three-month CME Term SOFR, as calculated and published by CME Group Benchmark Administration, Ltd. (a successor administrator), plus a tenor spread adjustment of 0.26 percent. Accordingly, the distribution rate on the Preferred Trust Securities is now three-month CME Term SOFR plus 1.137 percent.

The distribution rates paid were as follows during the years ended December 31:


	2023			2022			2021
Low distribution rate		5.64	%		1.05	%		0.99	%
High distribution rate		6.55	%		5.64	%		1.10	%
Distribution rate at the end of the year		6.51	%		5.64	%		1.05	%

Concurrent with the issuance of the Preferred Trust Securities, Avista Capital II issued $1.5 million of Common Trust Securities to the Company. These Preferred Trust Securities may be redeemed at the option of Avista Capital II at any time and mature on June 1, 2037. In December 2000, the Company purchased $10.0 million of these Preferred Trust Securities.

The Company owns 100 percent of Avista Capital II and has solely and unconditionally guaranteed the payment of distributions on, and redemption price and liquidation amount for, the Preferred Trust Securities to the extent Avista Capital II has funds available for such payments from the respective debt securities. Upon maturity or prior redemption of such debt

securities, the Preferred Trust Securities will be mandatorily redeemed. The Company does not include these capital trusts in its consolidated financial statements as Avista Corp. is not the primary beneficiary. As such, the sole assets of the capital trusts are $51.5 million of junior subordinated deferrable interest debentures of Avista Corp., which are reflected on the Consolidated Balance Sheets. Interest expense to affiliated trusts in the Consolidated Statements of Income represents interest expense on these debentures.

Pension Plans and Other Postretirement Benefit Plans

12 Months Ended

Dec. 31, 2023

Retirement Benefits, Description [Abstract]

Pension Plans and Other Postretirement Benefit Plans

NOTE 12. PENSION PLANS AND OTHER POSTRETIREMENT BENEFIT PLANS

The pension and other postretirement benefit plans described below only relate to Avista Utilities. AEL&P participates in a defined contribution multiemployer plan for its union workers and a defined contribution money purchase pension plan for its nonunion workers. None of the subsidiary retirement plans, individually or in the aggregate, are significant to Avista Corp.

Avista Utilities

The Company has a defined benefit pension plan covering the majority of regular full-time non-union employees at Avista Utilities hired prior to January 1, 2014 and regular full-time union employees that were hired prior to January 1, 2024. Employees eligible for the plan continue to accrue benefits. Individual benefits under this plan are based upon the employee’s years of service, date of hire and average compensation as specified in the plan. Non-union employees hired on or after January 1, 2014 and union employees hired on or after January 1, 2024 participate in a defined contribution 401(k) plan in lieu of a defined benefit pension plan. The Company’s funding policy is to contribute at least the minimum amounts required to be funded under the Employee Retirement Income Security Act, but not more than the maximum amounts currently deductible for income tax purposes. The Company contributed $10.0 million in cash to the pension plan in 2023, and $42.0 million in 2022 and 2021. The Company expects to contribute $10.0 million in cash to the pension plan in 2024.

In 2022, the defined benefit pension plan lump sum payments exceeded the annual service and interest costs for the plan. This resulted in a partial settlement of the plan, and the Company recorded a settlement loss of $11.8 million for the previously unrecognized losses in the year ended December 31, 2022. This loss was deferred as a regulatory asset and is being amortized over 12 years in accordance with regulatory accounting orders.

The Company has a SERP providing additional pension benefits to certain executive officers and certain key employees of the Company. The SERP provides benefits to individuals whose benefits under the defined benefit pension plan are reduced due to

the application of Section 415 of the Internal Revenue Code of 1986 and the deferral of salary under deferred compensation plans. The liability and expense for this plan are included as pension benefits in the tables included in this Note.

The Company expects benefit payments under the pension plan and the SERP will total (dollars in thousands):


	2024		2025		2026		2027		2028		Total 2029- 2033
Expected benefit payments	$	41,562	$	42,123	$	42,941	$	43,517	$	44,700	$	232,345

The expected long-term rate of return on plan assets is based on past performance and economic forecasts for the types of investments held by the plan. In selecting a discount rate, the Company considers yield rates for highly rated corporate bond portfolios with maturities similar to that of the expected term of pension benefits.

The Company provides certain health care and life insurance benefits for eligible retired employees hired prior to January 1, 2014. The Company accrues the estimated cost of postretirement benefit obligations during the years employees provide services. The liability and expense of this plan are included as other postretirement benefits. Non-union employees hired on or after January 1, 2014, will have access to the retiree medical plan upon retirement; however, Avista Corp. will no longer provide a contribution toward their medical premium.

The Company has a Health Reimbursement Arrangement (HRA) to provide employees with tax-advantaged funds to pay for allowable medical expenses upon retirement. The amount earned by the employee is fixed on the retirement date based on the employee’s years of service and the ending salary. The liability and expense of the HRA are included as other postretirement benefits.

The Company provides death benefits to beneficiaries of executive officers who die during their term of office or after retirement. Under the plan, an executive officer’s designated beneficiary will receive a payment equal to twice the executive officer’s annual base salary at the time of death (or if death occurs after retirement, a payment equal to twice the executive officer’s total annual pension benefit). The liability and expense for this plan are included as other postretirement benefits.

The Company expects benefit payments under other postretirement benefit plans will total (dollars in thousands):


	2024		2025		2026		2027		2028		Total 2029- 2033
Expected benefit payments	$	7,084	$	7,266	$	7,436	$	7,608	$	7,822	$	40,805

The Company expects to contribute $7.1 million to other postretirement benefit plans in 2024. The Company uses a December 31 measurement date for its pension and other postretirement benefit plans.

The following table sets forth the pension and other postretirement benefit plan disclosures as of December 31, 2023 and 2022 and the components of net periodic benefit costs for the years ended December 31, 2023, 2022 and 2021 (dollars in thousands):


	Pension Benefits						Other Post- retirement Benefits
	2023			2022			2023			2022
Change in benefit obligation:
Benefit obligation as of beginning of year	$	557,709		$	799,042		$	115,635		$	167,598
Service cost		14,350			23,877			2,394			4,369
Interest cost		33,245			26,536			6,766			5,503
Actuarial (gain)/loss		21,373			(204,775	)		4,799			(54,120	)
Plan change		—			3,302			—			—
Settlement		—			(60,206	)		—			—
Benefits paid		(41,432	)		(30,067	)		(7,210	)		(7,715	)
Benefit obligation as of end of year	$	585,245		$	557,709		$	122,384		$	115,635
Change in plan assets:
Fair value of plan assets as of beginning of year	$	540,703		$	750,963		$	49,472		$	59,544
Actual return on plan assets		78,838			(163,866	)		8,654			(10,072	)
Employer contributions		10,000			42,000			—			—
Settlement		—			(60,206	)		—			—
Benefits paid		(39,558	)		(28,188	)		—			—
Fair value of plan assets as of end of year	$	589,983		$	540,703		$	58,126		$	49,472
Funded status	$	4,738		$	(17,006	)	$	(64,258	)	$	(66,163	)
Amounts recognized in the Consolidated Balance Sheets:
Other non-current assets	$	32,997		$	13,382		$	—		$	—
Other current liabilities		(2,212	)		(1,934	)		(652	)		(706	)
Non-current liabilities		(26,047	)		(28,454	)		(63,606	)		(65,457	)
Net amount recognized	$	4,738		$	(17,006	)	$	(64,258	)	$	(66,163	)
Accumulated pension benefit obligation	$	514,295		$	495,654
Accumulated postretirement benefit obligation:
For retirees							$	68,087		$	61,984
For fully eligible employees							$	16,054		$	19,731
For other participants							$	38,243		$	33,920
Included in accumulated other comprehensive loss (income) (net of tax):
Unrecognized prior service cost (credit)	$	3,717		$	4,105		$	(1,081	)	$	(1,911	)
Unrecognized net actuarial loss		69,002			83,794			13,103			13,643
Total		72,719			87,899			12,022			11,732
Less regulatory asset		(71,983	)		(85,198	)		(12,401	)		(12,375	)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans	$	736		$	2,701		$	(379	)	$	(643	)


	Pension Benefits						Other Post- retirement Benefits
	2023			2022			2023			2022
Weighted-average assumptions as of December 31:
Discount rate for benefit obligation		5.86	%		6.10	%		5.83	%		6.10	%
Discount rate for annual expense		6.10	%		3.39	%		6.10	%		3.40	%
Expected long-term return on plan assets		8.30	%		5.80	%		7.20	%		4.70	%
Rate of compensation increase		4.87	%		4.69	%
Medical cost trend pre-age 65 – initial								6.50	%		6.25	%
Medical cost trend pre-age 65 – ultimate								5.00	%		5.00	%
Ultimate medical cost trend year pre-age 65							2030			2028
Medical cost trend post-age 65 – initial								6.50	%		6.25	%
Medical cost trend post-age 65 – ultimate								5.00	%		5.00	%
Ultimate medical cost trend year post-age 65							2030			2028


	Pension Benefits									Other Post-retirement Benefits
	2023			2022			2021			2023			2022			2021
Components of net periodic benefit cost:
Service cost (1)	$	14,350		$	23,877		$	25,306		$	2,394		$	4,369		$	4,114
Interest cost		33,245			26,536			26,160			6,766			5,503			5,139
Expected return on plan assets		(43,656	)		(43,872	)		(39,088	)		(3,562	)		(2,799	)		(2,400	)
Amortization of prior service cost (credit)		491			257			257			(1,050	)		(1,050	)		(921	)
Net loss recognition		4,915			4,180			6,645			319			3,344			3,865
Settlement loss (2)		—			11,828			—			—			—			—
Net periodic benefit cost	$	9,345		$	22,806		$	19,280		$	4,867		$	9,367		$	9,797

(1)

Total service costs in the table above are recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses.

(2)

The settlement loss was deferred as a regulatory asset and is being amortized over 12 years in accordance with regulatory accounting orders.

Plan Assets

The Finance Committee of the Board of Directors approves investment policies, objectives and strategies that seek an appropriate return for the pension plan and other postretirement benefit plans and reviews and approves changes to the investment and funding policies.

The Company has contracted with investment consultants who are responsible for monitoring the individual investment managers. The investment managers’ performance and related individual fund performance is periodically reviewed by an internal benefits committee and by the Finance Committee to monitor compliance with investment policy objectives and strategies.

Pension plan assets are invested in mutual funds, and trusts and partnerships that hold marketable debt and equity securities and real estate. In seeking to obtain a return that aligns with the funded status of the pension plan, the investment consultant recommends allocation percentages by asset classes. These recommendations are reviewed by the internal benefits committee, which then recommends their adoption by the Finance Committee. The Finance Committee has established target investment allocation percentages by asset classes and investment ranges for each asset class. The target investment allocation percentages are typically the midpoint of the established range. The target investment allocation percentages by asset classes are indicated in the table below:


	2023			2022
Equity securities		55	%		55	%
Debt securities		40	%		40	%
Real estate		5	%		5	%

The fair value of pension plan assets invested in debt and equity securities was based primarily on fair value (market prices). The fair value of investment securities traded on a national securities exchange is determined based on the reported last sales price; securities traded in the over-the-counter market are valued at the last reported bid price. Investment securities for which market prices are not readily available or for which market prices do not represent the value at the time of pricing, the investment manager estimates fair value based upon other inputs (including valuations of securities comparable in coupon, rating, maturity and industry).

Pension plan and other postretirement plan assets with fair values are measured using net asset value (NAV) are excluded from the fair value hierarchy and included as reconciling items in the tables below.

The plan's investments in common/collective trusts have redemption limitations that permit quarterly redemptions following notice requirements of 45 to 60 days. Most of the plan's investments in closely held investments and partnership interests have redemption limitations ranging from bi-monthly to semi-annually following redemption notice requirements of 60 to 90 days.

The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of the pension plan’s assets measured and reported as of December 31, 2023 at fair value (dollars in thousands):


	Level 1		Level 2		Level 3		Total
Cash equivalents	$	—	$	6,984	$	—	$	6,984
Fixed income securities:
U.S. government issues		—		19,293		—		19,293
Corporate issues		—		175,460		—		175,460
International issues		—		27,052		—		27,052
Municipal issues		—		13,772		—		13,772
Mutual funds:
U.S. equity securities		169,993		—		—		169,993
International equity securities		74,749		—		—		74,749
Plan assets measured at NAV (not subject to hierarchy disclosure)
Common/collective trusts: real estate		—		—		—		25,284
Partnership/closely held investments:
International equity securities		—		—		—		70,652
Real estate		—		—		—		6,744
Total	$	244,742	$	242,561	$	—	$	589,983


	Level 1		Level 2		Level 3		Total
Cash equivalents	$	—	$	5,110	$	—	$	5,110
Fixed income securities:
U.S. government issues		—		16,732		—		16,732
Corporate issues		—		161,180		—		161,180
International issues		—		23,108		—		23,108
Municipal issues		—		13,427		—		13,427
Mutual funds:
U.S. equity securities		154,442		—		—		154,442
International equity securities		58,933		—		—		58,933
Plan assets measured at NAV (not subject to hierarchy disclosure)
Common/collective trusts: real estate		—		—		—		30,406
Partnership/closely held investments:
International equity securities		—		—		—		69,792
Real estate		—		—		—		7,573
Total	$	213,375	$	219,557	$	—	$	540,703

The fair value of other postretirement plan assets invested in debt and equity securities was based primarily on market prices. The fair value of investment securities traded on a national securities exchange is determined based on the last reported sales price; securities traded in the over-the-counter market are valued at the last reported bid price. For investment securities for which market prices are not readily available, the investment manager determines fair value based upon other inputs (including valuations of securities comparable in coupon, rating, maturity and industry). The target asset allocation was 60 percent equity securities and 40 percent debt securities in both 2023 and 2022.

The fair value of other postretirement plan assets was determined to be $58.1 million and $49.5 million as of December 31, 2023 and 2022, respectively. The assets consist of a balanced index mutual fund, which is a single mutual fund that includes a percentage of U.S. equity and fixed income securities and International equity and fixed income securities. This mutual fund is classified as Level 1 in the fair value hierarchy (see Note 18 for a description of the fair value hierarchy).

401(k) Plans and Executive Deferral Plan

Avista Utilities has a salary deferral 401(k) plan that is a defined contribution plan and covers substantially all employees. Employees can make contributions to their respective accounts in the plans on a pre-tax basis up to the maximum amount permitted by law. The Company matches a portion of the salary deferred by each participant according to the schedule in the respective plan.

Employer matching contributions were as follows for the years ended December 31 (dollars in thousands):


	2023		2022		2021
Employer 401(k) matching contributions	$	15,022	$	13,258	$	11,671

The Company has an Executive Deferral Plan. This plan allows executive officers and other key employees the opportunity to defer until the earlier of their retirement, termination, disability or death, up to 75 percent of their base salary and/or up to 100 percent of their incentive payments. Deferred compensation funds are held by the Company in a Rabbi Trust.

There were deferred compensation assets included in other property and investments-net and corresponding deferred compensation liabilities included in other non-current liabilities and deferred credits on the Consolidated Balance Sheets of the following amounts as of December 31 (dollars in thousands):


	2023		2022
Deferred compensation assets and liabilities	$	7,794	$	7,541

The entire disclosure for retirement benefits.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 60
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

Pension Plans and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Costs (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Pension Plan And SERP [Member]

$ 11,800

^[1]

$ 14,350

23,877

$ 25,306

Expected return on plan assets

33,245

26,536

26,160

$ (43,656)

$ (43,872)

$ (39,088)

Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]

Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax

Amortization of prior service cost

$ 491

$ 257

Net loss recognition

4,915

4,180

6,645

Net periodic benefit cost

^[2]

11,828

9,345

22,806

19,280

^[1]

2,394

4,369

4,114

Expected return on plan assets

6,766

5,503

5,139

$ (3,562)

$ (2,799)

$ (2,400)

Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]

Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax

Amortization of prior service cost

$ (1,050)

$ (921)

Net loss recognition

319

3,344

3,865

Net periodic benefit cost

$ 4,867

$ 9,367

$ 9,797

[1]	Total service costs in the table above are recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses.
[2]	The settlement loss was deferred as a regulatory asset and is being amortized over 12 years in accordance with regulatory accounting orders.

Equity Investments - Summary of Net Unrealized Gains Related to Investments without Readily Determinable Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity Investments [Line items]
Total	$ 4,323	$ 45,667	$ 8,761
Recurring fair value [Member]
Equity Investments [Line items]
Unrealized gain	4,323	33,382	0
Non-recurring fair value [Member]
Equity Investments [Line items]
Unrealized gain	$ 0	$ 12,285	$ 8,761

Property, Plant And Equipment - Schedule of Major Classifications of Property, Plant And Equipment (Parenthetical) (Details) - Corporate and Other [Member] - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation		$ 2,400,000
Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ 100,000

Derivatives and Risk Management - Schedule of Energy Commodity Derivative Volumes (Details) MWh in Thousands, MMBTU in Thousands	12 Months Ended
	Dec. 31, 2023 MMBTU MWh	Dec. 31, 2022 MMBTU MWh
Purchase [Member] \| Physical [Member] \| Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one \| MWh	9	5
Year two \| MWh	0	0
Year three \| MWh	0	0
Purchase [Member] \| Physical [Member] \| Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one \| MMBTU	22,747	19,140
Year two \| MMBTU	12,505	533
Year three \| MMBTU	5,570	450
Purchase [Member] \| Financial [Member] \| Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one \| MWh	0	0
Year two \| MWh	0	0
Year three \| MWh	0	0
Purchase [Member] \| Financial [Member] \| Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one \| MMBTU	74,596	79,253
Year two \| MMBTU	19,590	30,658
Year three \| MMBTU	3,940	4,895
Sales [Member] \| Physical [Member] \| Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one \| MWh	472	136
Year two \| MWh	11	0
Year three \| MWh	0	0
Sales [Member] \| Physical [Member] \| Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one \| MMBTU	1,723	4,145
Year two \| MMBTU	1,115	1,370
Year three \| MMBTU	0	1,115
Sales [Member] \| Financial [Member] \| Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one \| MWh	510	1,011
Year two \| MWh	96	0
Year three \| MWh	0	0
Sales [Member] \| Financial [Member] \| Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one \| MMBTU	12,038	29,473
Year two \| MMBTU	1,125	9,668
Year three \| MMBTU	0	1,125

Energy Purchase Contracts

12 Months Ended

Dec. 31, 2023

Energy Purchase Contracts [Abstract]

Energy Purchase Contracts

NOTE 14. ENERGY PURCHASE CONTRACTS

The below discussion only relates to Avista Utilities. The sole energy purchase contract at AEL&P is a PPA for the Snettisham hydroelectric project and it is accounted for as a lease. AEL&P does not have any other significant operating agreements or contractual obligations. See Note 5 for further discussion of the Snettisham PPA.

Avista Utilities has contracts for the purchase of fuel for thermal generation, natural gas for resale and various agreements for the purchase or exchange of electric energy with other entities. The remaining term of the contracts range from one month to twenty-five years.

Total expenses for power purchased, natural gas purchased, fuel for generation and other fuel costs, which are included in utility resource costs in the Consolidated Statements of Income, were as follows for the years ended December 31 (dollars in thousands):


	2023		2022		2021
Utility power resources	$	607,155	$	660,967	$	431,199

The following table details Avista Utilities’ future contractual commitments for power resources (including transmission contracts) and natural gas resources (including transportation contracts) (dollars in thousands):


	2024		2025		2026		2027		2028		Thereafter		Total
Power resources	$	336,766	$	293,389	$	266,251	$	235,751	$	234,756	$	2,245,762	$	3,612,675
Natural gas resources		122,241		81,141		46,033		41,708		41,168		280,562		612,853
Total	$	459,007	$	374,530	$	312,284	$	277,459	$	275,924	$	2,526,324	$	4,225,528

These energy purchase contracts were entered into as part of Avista Utilities’ obligation to serve its retail electric and natural gas customers’ energy requirements, including contracts entered into for resource optimization. These costs are recovered either through base retail rates or adjustments to retail rates as part of the power and natural gas cost deferral and recovery mechanisms.

The future contractual commitments for power resources include fixed contractual amounts related to the Company's contracts with PUDs to purchase portions of the output of certain generating facilities. Although Avista Utilities has no investment in the PUD generating facilities, the contracts obligate Avista Utilities to pay certain minimum amounts whether or not the facilities are operating. The cost of power obtained under the contracts, including payments made when a facility is not operating, is included in utility resource costs in the Consolidated Statements of Income. The contractual amounts included above consist of Avista Utilities’ share of existing debt service cost and its proportionate share of the variable operating expenses of these projects. The minimum amounts payable under these contracts are based in part on the proportionate share of the debt service requirements of the PUD's revenue bonds for which the Company is indirectly responsible. The Company's total future debt service obligation associated with the revenue bonds outstanding at December 31, 2023 (principal and interest) was $275.1 million.

In addition, Avista Utilities has operating agreements, settlements and other contractual obligations related to its generating facilities and transmission and distribution services. The expenses associated with these agreements are reflected as other operating expenses in the Consolidated Statements of Income. The following table details future contractual commitments under these agreements (dollars in thousands):


	2024		2025		2026		2027		2028		Thereafter		Total
Contractual obligations	$	39,156	$	40,226	$	18,630	$	19,085	$	9,390	$	177,553	$	304,040

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares, issued	78,074,587	74,945,948
Common stock, shares outstanding	78,074,587	74,945,948

Balance Sheet Components - Schedule of Other Non-Current Liabilities and Deferred Credits (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Operating lease liabilities	$ 63,559	$ 64,284
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Total	Total
Finance lease liabilities	$ 39,095	$ 42,495
Deferred investment tax credits	28,233	28,784
Climate Commitment Act obligations	26,026
Asset retirement obligations	18,058	15,783	$ 17,142	$ 17,194
Derivative liabilities	17,902	7,892
Other	17,357	16,617
Total	$ 210,230	$ 175,855

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 171,180	$ 155,176	$ 147,334
Other Comprehensive Income :
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes of $452, $2,387 and $888, respectively	1,701	8,981	3,339
Total other comprehensive income	1,701	8,981	3,339
Comprehensive income	$ 172,881	$ 164,157	$ 150,673

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Jointly Owned Utility Plant, Net Ownership Amount [Abstract]

Jointly Owned Electric Facilities

12 Months Ended

Dec. 31, 2023

Jointly Owned Electric Facilities

NOTE 9. JOINTLY OWNED ELECTRIC FACILITIES

The Company has a 15 percent ownership interest in Units 3 and 4 of Colstrip, and provides financing for its ownership interest in the project. Pursuant to the ownership and operating agreements among the co-owners, the Company’s share of related fuel costs as well as operating expenses for plant in service are included in the corresponding accounts in the Consolidated Statements of Income. The Company’s share of utility plant in service for Colstrip and accumulated depreciation (inclusive of the ARO assets and accumulated amortization) were as follows as of December 31 (dollars in thousands):


	2023			2022
Utility plant in service	$	394,398		$	390,852
Accumulated depreciation		(334,338	)		(315,223	)

See Note 11 for further discussion of AROs.

While the obligations and liabilities with respect to Colstrip are to be shared among the co-owners on a pro-rata basis, many of the environmental liabilities are joint and several under the law, so that if any co-owner failed to pay its share of such liability, the other co-owners (or any one of them) could be required to pay the defaulting co-owner‘s share (or the entire liability).

In January 2023, the Company entered into an agreement with NorthWestern to transfer its ownership in Colstrip Units 3 and 4. The Company will retain responsibility for remediation obligations in existence at the time the transaction closes. See further discussion of the transaction within Note 22.

Accounting For Income Taxes - Schedule of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred income tax assets:
Regulatory liabilities	$ 192,099	$ 197,998
Tax credits and net operating loss carryforwards	76,969	74,782
Provisions for pensions	19,100	20,132
Other	47,839	54,903
Total gross deferred income tax assets	336,007	347,815
Valuation allowances for deferred tax assets	(10,461)	(3,874)
Total deferred income tax assets after valuation allowances	325,546	343,941
Deferred income tax liabilities:
Utility property, plant, and equipment	746,876	712,470
Regulatory assets	268,833	281,483
Other	28,155	24,983
Total deferred income tax liabilities	1,043,864	1,018,936
Net long-term deferred income tax liability	$ 718,318	$ 674,995

Long-Term Debt to Affiliated Trusts - Schedule of Distribution Rates Paid (Details) - Trust Preferred Securities Subject to Mandatory Redemption [Member]	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Interest rate	6.51%	5.64%	1.05%
Minimum [Member]
Debt Instrument [Line Items]
Interest rate	5.64%	1.05%	0.99%
Maximum [Member]
Debt Instrument [Line Items]
Interest rate	6.55%	5.64%	1.10%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Long Term Debt To Affiliated Trust [Abstract]

Property, Plant And Equipment - Schedule of Net Utility Property (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Utility plant in service	$ 7,799,481	$ 7,561,688
Construction work in progress	179,527	164,147
Total	7,979,008	7,725,835
Less: Accumulated depreciation and amortization	2,278,952	2,281,126
Total net utility property	$ 5,700,056	$ 5,444,709

Pension Plans and Other Postretirement Benefit Plans - Deferred Compensation Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred Compensation, Excluding Share-based Payments and Retirement Benefits [Member]
Deferred Compensation Arrangement With Individual Excluding Share Based Payments And Postretirement Benefits [Line Items]
Deferred compensation assets and liabilities	$ 7,794	$ 7,541

Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Leases

NOTE 5. LEASES

The core principle of lease accounting is that an entity should recognize the ROU assets and liabilities from leases on the balance sheet and depreciate or amortize the asset and liability over the term of the lease, as well as provide disclosure to enable users of the consolidated financial statements to assess the amount, timing, and uncertainty of cash flows from leases.

Significant Judgments and Assumptions

The Company determines if an arrangement is a lease, as well as its classification, at its inception.

ROU assets represent the Company's right to use an underlying asset for the lease term, and lease liabilities represent the Company's obligation to make lease payments. Operating and finance lease ROU assets and lease liabilities are recognized at the commencement date of the agreement based on the present value of lease payments over the lease term. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date to determine the present value of lease payments. The implicit rate is used when it is

readily determinable. The operating and finance lease ROU assets also includes lease payments made and exclude lease incentives, if any, that accrue to the benefit of the lessee.

Lease terms may include options to extend or terminate the lease when it is reasonably certain the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. The difference between lease expense and cash paid for leased assets is recognized as a regulatory asset or regulatory liability.

Description of Leases

Operating Leases

The Company's most significant operating lease is with the State of Montana associated with submerged land around the Company's hydroelectric facilities in the Clark Fork River basin, which expires in 2046. The terms of this lease are subject to adjustment - depending on the outcome of ongoing litigation between the State of Montana and NorthWestern. In addition, the State of Montana and Avista Corp. were engaged in litigation regarding lease terms, including how much money, if any, the State of Montana should return to Avista Corp.; however, that litigation was dismissed as premature pending the outcome of the ongoing litigation between the State of Montana and NorthWestern. Any reduction in future lease payments or the return to Avista Corp. of amounts previously paid will be included in the future ratemaking process.

In addition to the lease with the State of Montana, the Company has other operating leases for land associated with its utility operations, as well as communication sites which support network and radio communications within its service territory. The Company's leases have remaining terms of 1 to 70 years. Most of the Company's leases include options to extend the lease term for periods of 5 to 50 years. Options are exercised at the Company's discretion.

Certain of the Company's lease agreements include rental payments which are periodically adjusted over the term of the agreement based on the consumer price index. The Company's lease agreements do not include material residual value guarantees or material restrictive covenants.

In March 2023, the Company entered into an agreement with Rathdrum Power, LLC amending and restating a PPA for the output of the Lancaster Plant. The restated PPA meets the accounting definition of a lease, and all payments are variable in nature, based on capacity, usage, or performance of the plant. Therefore, there is no lease obligation or corresponding ROU asset recorded by the Company related to this agreement. The variable lease costs related to this agreement are included in resource costs on the Consolidated Statements of Income.

Avista Corp. does not record leases with a term of 12 months or less in the Consolidated Balance Sheets. Total short-term lease costs for the year ended December 31, 2023 are immaterial.

Finance Lease

AEL&P has a PPA which is a finance lease for accounting purposes related to the Snettisham hydroelectric project, which expires in 2034. For ratemaking purposes, this lease is an operating lease with a constant level of annual rental expense (straight line rent expense). Because of this regulatory treatment, differences between the operating lease expense for ratemaking purposes and the expenses recognized under GAAP (interest expense and amortization of the finance lease ROU asset) are recorded as a regulatory asset and amortized during the later years of the lease when the finance lease expense is less than the operating lease expense included in base rates. The amortization of the ROU asset is included in depreciation and amortization and the interest associated with the lease liability is included in interest expense on the Consolidated Statements of Income.

The components of lease expense were as follows for the year ended December 31 (dollars in thousands):


	2023		2022		2021
Operating lease cost:
Fixed lease cost (Other operating expenses)	$	5,096	$	4,986	$	4,970
Variable lease cost (Other operating expenses and Resource costs)		24,628		1,567		1,180
Total operating lease cost	$	29,724	$	6,553	$	6,150

Finance lease cost:
Amortization of ROU asset (Depreciation and amortization)	$	3,641	$	3,641	$	3,641
Interest on lease liabilities (Interest expense)		2,221		2,375		2,522
Total finance lease cost	$	5,862	$	6,016	$	6,163

Supplemental cash flow information related to leases was as follows for the year ended December 31 (dollars in thousands):


	2023		2022		2021
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash outflows:
Operating lease payments	$	4,960	$	4,828	$	4,805
Interest on finance lease		2,221		2,375		2,522
Total operating cash outflows	$	7,181	$	7,203	$	7,327

Finance cash outflows:
Principal payments on finance lease	$	3,235	$	3,085	$	2,935

Supplemental balance sheet information related to leases was as follows for December 31 (dollars in thousands):


	December 31,			December 31,
	2023			2022
Operating Leases
Operating lease ROU assets (Other property and investments-net and other non-current assets)	$	67,585		$	68,238

Other current liabilities	$	4,490		$	4,349
Other non-current liabilities and deferred credits		63,559			64,284
Total operating lease liabilities	$	68,049		$	68,633

Finance Leases
Finance lease ROU assets (Other property and investments-net and other non-current assets)	$	36,414		$	40,056

Other current liabilities	$	3,400		$	3,235
Other non-current liabilities and deferred credits		39,095			42,495
Total finance lease liabilities	$	42,495		$	45,730

Weighted Average Remaining Lease Term
Operating leases	22.28 years			23.28 years
Finance leases	4.53 years			5.42 years

Weighted Average Discount Rate
Operating leases		4.29	%		4.28	%
Finance leases		3.77	%		4.07	%

Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2023 (dollars in thousands):


	Operating Leases			Finance Leases
2024	$	4,988		$	5,459
2025		4,984			5,454
2026		4,981			5,456
2027		5,007			5,458
2028		4,992			5,456
Thereafter		83,532			27,292
Total lease payments	$	108,484		$	54,575
Less: imputed interest		(40,435	)		(12,080	)
Total	$	68,049		$	42,495

Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2022 (dollars in thousands):


	Operating Leases			Finance Leases
2023	$	4,850		$	5,456
2024		4,877			5,459
2025		4,884			5,454
2026		4,869			5,456
2027		4,880			5,458
Thereafter		86,991			32,748
Total lease payments	$	111,351		$	60,031
Less: imputed interest		(42,718	)		(14,301	)
Total	$	68,633		$	45,730

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Utility revenues:
Utility revenues, exclusive of alternative revenue programs	$ 1,746,097	$ 1,742,876	$ 1,445,000
Alternative revenue programs	4,899	(33,357)	(6,635)
Total utility revenues	1,750,996	1,709,519	1,438,365
Non-utility revenues	558	688	571
Total operating revenues	1,751,554	1,710,207	1,438,936
Utility operating expenses:
Resource costs	702,372	735,862	497,123
Other operating expenses	413,608	405,165	366,125
Depreciation and amortization	265,329	253,017	231,915
Taxes other than income taxes	109,715	114,193	109,353
Non-utility operating expenses	2,840	11,728	6,188
Total operating expenses	1,493,864	1,519,965	1,210,704
Income from operations	257,690	190,242	228,232
Interest expense	140,795	117,634	105,731
Interest expense to affiliated trust	2,504	1,058	421
Capitalized interest	(3,633)	(3,718)	(3,987)
Other income-net	(19,526)	(62,717)	(33,298)
Income before income taxes	137,550	137,985	159,365
Income tax expense (benefit)	(33,630)	(17,191)	12,031
Net income	$ 171,180	$ 155,176	$ 147,334
Weighted-average common shares outstanding (thousands), basic	76,396	72,989	69,951
Weighted-average common shares outstanding (thousands), diluted	76,495	73,093	70,085
Earnings per common share:
Basic	$ 2.24	$ 2.13	$ 2.11
Diluted	$ 2.24	$ 2.12	$ 2.1

Revenue - Schedule of Utilities Operating Revenue Expense Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Utility-related taxes	$ 75,404	$ 69,931	$ 62,736

Long-Term Debt to Affiliated Trusts (Tables)

12 Months Ended

Dec. 31, 2023

Schedule of Distribution Rates Paid

The distribution rates paid were as follows during the years ended December 31:


	2023			2022			2021
Low distribution rate		5.64	%		1.05	%		0.99	%
High distribution rate		6.55	%		5.64	%		1.10	%
Distribution rate at the end of the year		6.51	%		5.64	%		1.05	%

Information by Business Segments (Tables)

12 Months Ended

Dec. 31, 2022

Segment Reporting [Abstract]

Schedule of Business Segments

The following table presents information for each of the Company’s business segments (dollars in thousands):


	Avista Utilities			Alaska Electric Light and Power Company		Total Utility			Other			Intersegment Eliminations (1)			Total
For the year ended December 31, 2023
Operating revenues	$	1,702,857		$	48,139	$	1,750,996		$	558		$	—		$	1,751,554
Resource costs		698,546			3,826		702,372			—			—			702,372
Other operating expenses		398,523			15,085		413,608			2,760			—			416,368
Depreciation and amortization		254,401			10,928		265,329			80			—			265,409
Income (loss) from operations		242,678			17,294		259,972			(2,282	)		—			257,690
Interest expense (2)		136,924			5,852		142,776			1,881			(1,358	)		143,299
Income tax expense (benefit)		(35,353	)		3,315		(32,038	)		(1,592	)		—			(33,630	)
Net income (loss)		167,016			8,937		175,953			(4,773	)		—			171,180
Capital expenditures (3)		484,716			13,921		498,637			—			—			498,637
For the year ended December 31, 2022
Operating revenues	$	1,663,815		$	45,704	$	1,709,519		$	688		$	—		$	1,710,207
Resource costs		732,298			3,564		735,862			—			—			735,862
Other operating expenses		390,597			14,568		405,165			11,603			—			416,768
Depreciation and amortization		242,198			10,819		253,017			125			—			253,142
Income (loss) from operations		185,582			15,700		201,282			(11,040	)		—			190,242
Interest expense (2)		112,213			5,960		118,173			791			(272	)		118,692
Income tax expense (benefit)		(27,368	)		2,337		(25,031	)		7,840			—			(17,191	)
Net income		117,901			7,545		125,446			29,730			—			155,176
Capital expenditures (3)		443,373			8,622		451,995			834			—			452,829
For the year ended December 31, 2021
Operating revenues	$	1,392,999		$	45,366	$	1,438,365		$	571		$	—		$	1,438,936
Resource costs		493,289			3,834		497,123			—			—			497,123
Other operating expenses		352,241			13,884		366,125			5,927			—			372,052
Depreciation and amortization		221,552			10,363		231,915			261			—			232,176
Income (loss) from operations		217,663			16,186		233,849			(5,617	)		—			228,232
Interest expense (2)		99,629			6,096		105,725			522			(95	)		106,152
Income tax expense		6,029			2,763		8,792			3,239			—			12,031
Net income		125,558			7,224		132,782			14,552			—			147,334
Capital expenditures (3)		435,887			4,052		439,939			1,270			—			441,209
Total Assets:
As of December 31, 2023	$	7,262,704		$	269,683	$	7,532,387		$	191,665		$	(21,575	)	$	7,702,477
As of December 31, 2022		6,976,164			264,322		7,240,486			187,027			(10,163	)		7,417,350
As of December 31, 2021		6,458,244			265,422		6,723,666			132,158			(2,241	)		6,853,583

(1)

Intersegment eliminations reported as interest expense represent intercompany interest. Intersegment eliminations reported as assets represent intersegment accounts receivable.

(2)

Including interest expense to affiliated trusts.

(3)

The capital expenditures for the other businesses are included in other investing activities on the Consolidated Statements of Cash Flows.

Energy Purchase Contracts (Future Contractual Commitments For Power Resources And Natural Gas Resources) (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Energy Purchase Contracts [Line Items]
2023	$ 459,007
2024	374,530
2025	312,284
2026	277,459
2027	275,924
Thereafter	2,526,324
Total	4,225,528
Power Resources [Member]
Energy Purchase Contracts [Line Items]
2023	336,766
2024	293,389
2025	266,251
2026	235,751
2027	234,756
Thereafter	2,245,762
Total	3,612,675
Natural Gas Resources [Member]
Energy Purchase Contracts [Line Items]
2023	122,241
2024	81,141
2025	46,033
2026	41,708
2027	41,168
Thereafter	280,562
Total	612,853
Generation Transmission And Distribution Facilities [Member]
Energy Purchase Contracts [Line Items]
2023	39,156
2024	40,226
2025	18,630
2026	19,085
2027	9,390
Thereafter	177,553
Total	$ 304,040

Leases - Summary of Supplemental Balance Sheet Information Related to Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Operating lease ROU assets	$ 67,585	$ 68,238
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other property and investments-net and other non-current assets	Other property and investments-net and other non-current assets
Operating Lease, Liability, Current	$ 4,490	$ 4,349
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Operating Lease, Liability, Noncurrent	$ 63,559	$ 64,284
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Operating Lease, Liability	$ 68,049	$ 68,633
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Liabilities	Liabilities
Finance lease ROU assets	$ 36,414	$ 40,056
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other property and investments-net and other non-current assets	Other property and investments-net and other non-current assets
Finance Lease, Liability, Current	$ 3,400	$ 3,235
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Finance Lease, Liability, Noncurrent	$ 39,095	$ 42,495
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Noncurrent	Other Liabilities, Noncurrent
Finance Lease, Liability	$ 42,495	$ 45,730
Operating leases, Weighted Average Remaining Lease Term	22 years 3 months 10 days	23 years 3 months 10 days
Finance leases, Weighted Average Remaining Lease Term	4 years 6 months 10 days	5 years 5 months 1 day
Operating leases, Weighted Average Discount Rate	4.29%	4.28%
Finance leases, Weighted Average Discount Rate	3.77%	4.07%

Accounting For Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense

Income tax expense consisted of the following for the years ended December 31 (dollars in thousands):


	2023			2022			2021
Current income tax expense	$	3,207		$	1,040		$	807
Deferred income tax expense (benefit)		(36,837	)		(18,231	)		11,224
Total income tax expense (benefit)	$	(33,630	)	$	(17,191	)	$	12,031

Schedule of Effective Income Tax Rate Reconciliation


	2023					2022					2021
Federal income taxes at statutory rates	$	28,886		21.0	%	$	28,977		21.0	%	$	33,467		21.0	%
Increase (decrease) in tax resulting from:
Tax effect of regulatory treatment of utility plant differences (1)		(12,270	)	(8.9	)		(12,366	)	(9.0	)		(13,820	)	(8.7	)
State income tax expense		2,077		1.5			1,676		1.2			1,385		0.8
Flow through related to deduction of meters and mixed service costs (2)		(47,983	)	(34.9	)		(34,454	)	(25.0	)		(8,678	)	(5.4	)
Tax credits		(2,334	)	(1.7	)		(258	)	(0.2	)		(75	)	—
Other		(2,006	)	(1.4	)		(766	)	(0.5	)		(248	)	(0.2	)
Total income tax expense (benefit)	$	(33,630	)	(24.4	)%	$	(17,191	)	(12.5	)%	$	12,031		7.5	%

(1)

(2)

Schedule of Deferred Income Tax Assets and Liabilities

The total net deferred income tax liability consisted of the following as of December 31 (dollars in thousands):


	2023			2022
Deferred income tax assets:
Regulatory liabilities	$	192,099		$	197,998
Tax credits and net operating loss carryforwards		76,969			74,782
Provisions for pensions		19,100			20,132
Other		47,839			54,903
Total gross deferred income tax assets		336,007			347,815
Valuation allowances for deferred tax assets		(10,461	)		(3,874	)
Total deferred income tax assets after valuation allowances		325,546			343,941
Deferred income tax liabilities:
Utility property, plant, and equipment		746,876			712,470
Regulatory assets		268,833			281,483
Other		28,155			24,983
Total deferred income tax liabilities		1,043,864			1,018,936
Net long-term deferred income tax liability	$	718,318		$	674,995

New Accounting Standards

12 Months Ended

Dec. 31, 2023

Accounting Standards Update and Change in Accounting Principle [Abstract]

New Accounting Standards

NOTE 2. NEW ACCOUNTING STANDARDS

ASU 2022-03 "Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions"

In June 2022, the FASB issued ASU 2022-03, Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions. The purpose of this guidance is to clarify that a contractual restriction on the ability to sell an equity security is not considered part of the unit of account of the equity security, and therefore should not be considered when measuring the equity security's fair value. Additionally, an entity cannot separately recognize and measure a contractual sale restriction. This guidance also adds specific disclosures related to equity securities subject to contractual sale restrictions, including (i) the fair value of equity securities subject to contractual sale restrictions reflected in the balance sheet, (ii) the nature and remaining duration of the restrictions and (iii) the circumstances that could cause a lapse in the restrictions. The amendments are effective on January 1, 2024, with early adoption permitted. The amendments must be applied using a prospective approach with adjustments from the adoption of the amendments recognized in earnings and disclosed upon adoption. The Company expects these amendments to only affect its disclosure requirements.

ASU 2023-06 "Disclosure Improvements - Codification Amendments in Response to the SEC's Disclosure Update and Simplification Initiative"

In October 2023, the FASB issued ASU 2023-06, which incorporates a variety of SEC required disclosures into the FASB Accounting Standards Codification (ASC). For entities subject to SEC's existing disclosure requirements, the effective date for each amendment will be the date on which the SEC removes the related disclosure from Regulation S-X or Regulation S-K, with early adoption permitted. If the SEC has not removed the applicable requirement from Regulation S-X or Regulation S-K by June 30, 2027, the disclosure requirements will be removed from the Codification. The requirements of the ASU will not have a material impact on the Company's financial statements.

ASU 2023-07 "Segment Reporting (Topic 280) - Improvements to Reportable Segment Disclosures"

In November 2023, the FASB issued ASU 2023-07, requiring additional disclosures around reportable segment information. The additional required disclosures include significant segment expenses, an amount for other segment activity not included in the disaggregated segment amounts and a description of the activity, and the title and position of the chief operating decision maker and an explanation of how they use the reported measures of segment profit or loss in assessing segment performance and allocating resources. The ASU is effective for fiscal years beginning after December 15, 2023 and interim periods beginning after December 15, 2024, and early adoption is permitted. The Company is in the process of evaluating the impact of the ASU; however, it has determined it will not early adopt as of December 31, 2023.

ASU 2023-09 "Income Taxes (Topic 740) - Improvements to Income Tax Disclosures"

In December 2023, the FASB issued ASU 2023-09, requiring additional income tax disclosures. The additional disclosures include prescribed items presented in the income tax rate reconciliation, and further disaggregation of income taxes paid amounts between federal, state and foreign taxes. The ASU is effective for fiscal years beginning after December 15, 2024 and early adoption is permitted. The Company is in the process of evaluating the impact of the ASU; however, it has determined it will not early adopt as of December 31, 2023.

The entire disclosure for change in accounting principle. Includes, but is not limited to, nature, reason, and method of adopting amendment to accounting standards or other change in accounting principle.

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Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 171,180	$ 155,176	$ 147,334

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

Asset Retirement Obligation Disclosure [Abstract]

Leases - Summary of Supplemental Cash Flow Information related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating cash outflows:
Operating lease payments	$ 4,960	$ 4,828	$ 4,805
Interest on finance lease	2,221	2,375	2,522
Total operating cash outflows	7,181	7,203	7,327
Finance cash outflows:
Principal payments on finance lease	$ 3,235	$ 3,085	$ 2,935

Asset Retirement Obligations

12 Months Ended

Dec. 31, 2023

Asset Retirement Obligations

NOTE 11. ASSET RETIREMENT OBLIGATIONS

The Company has recorded liabilities for future AROs to:

•

restore coal ash containment ponds and coal holding areas at Colstrip,

•

cap a landfill at the Kettle Falls Plant, and

•

remove plant and restore the land at the Coyote Springs 2 site at the termination of the land lease.

Due to an inability to estimate a range of settlement dates, the Company cannot estimate a liability for the:

•

removal and disposal of certain transmission and distribution assets, and

•

abandonment and decommissioning of certain hydroelectric generation and natural gas storage facilities.

In 2015, the EPA issued a final rule regarding CCRs. Colstrip produces this byproduct. The CCR rule has been the subject of ongoing litigation. In August 2018, the D.C. Circuit struck down provisions of the rule. The rule includes technical requirements for CCR landfills and surface impoundments. The Colstrip owners developed a multi-year compliance plan to address the CCR requirements and existing state obligations.

The actual asset retirement costs related to the CCR rule requirements may vary substantially from the estimates used to record the ARO due to the uncertainty and evolving nature of the compliance strategies that will be used and the availability of data used to estimate costs, such as the quantity of coal ash present at certain sites and the volume of fill that will be needed to cap and cover certain impoundments. The Company updates its estimates as new information becomes available. The Company expects to seek recovery of costs related to complying with the CCR rule through the ratemaking process.

In addition to the above, under a 2018 Administrative Order on Consent and ongoing negotiations with the Montana Department of Ecological Quality, the owners of Colstrip are required to provide financial assurance, primarily in the form of surety bonds, to secure each owner's pro-rata share of various anticipated closure and remediation of the ash ponds and coal holding areas. The amount of financial assurance required of each owner may, like the ARO, vary substantially due to the uncertainty and evolving nature of anticipated closure and remediation activities, and as those activities are completed over time.

The following table documents the changes in the Company’s asset retirement obligation during the years ended December 31 (dollars in thousands):


	2023			2022			2021
Asset retirement obligation at beginning of year	$	15,783		$	17,142		$	17,194
Liabilities incurred		1,927			—			825
Liabilities settled		(232	)		(1,964	)		(1,541	)
Accretion expense		580			605			664
Asset retirement obligation at end of year	$	18,058		$	15,783		$	17,142

Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2023

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Changes in Asset Retirement Obligation

The following table documents the changes in the Company’s asset retirement obligation during the years ended December 31 (dollars in thousands):


	2023			2022			2021
Asset retirement obligation at beginning of year	$	15,783		$	17,142		$	17,194
Liabilities incurred		1,927			—			825
Liabilities settled		(232	)		(1,964	)		(1,541	)
Accretion expense		580			605			664
Asset retirement obligation at end of year	$	18,058		$	15,783		$	17,142

Energy Purchase Contracts (Tables)

12 Months Ended

Dec. 31, 2023

Energy Purchase Contracts [Line Items]

Schedule of Utility Total Expenses


	2023		2022		2021
Utility power resources	$	607,155	$	660,967	$	431,199

Future Contractual Commitments for Power Resources and Natural Gas Resources


	2024		2025		2026		2027		2028		Thereafter		Total
Power resources	$	336,766	$	293,389	$	266,251	$	235,751	$	234,756	$	2,245,762	$	3,612,675
Natural gas resources		122,241		81,141		46,033		41,708		41,168		280,562		612,853
Total	$	459,007	$	374,530	$	312,284	$	277,459	$	275,924	$	2,526,324	$	4,225,528

Contractual Obligations [Member]

Energy Purchase Contracts [Line Items]

Future Contractual Commitments for Power Resources and Natural Gas Resources

The following table details future contractual commitments under these agreements (dollars in thousands):


	2024		2025		2026		2027		2028		Thereafter		Total
Contractual obligations	$	39,156	$	40,226	$	18,630	$	19,085	$	9,390	$	177,553	$	304,040

Revenue - Additional Information (Details) $ in Millions	Dec. 31, 2023 USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 7.4

Asset Retirement Obligations - Schedule of Changes in Asset Retirement Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Asset Retirement Obligation Disclosure [Abstract]
Asset retirement obligation at beginning of year	$ 15,783	$ 17,142	$ 17,194
Liabilities incurred	1,927		825
Liabilities settled	(232)	(1,964)	(1,541)
Accretion expense	580	605	664
Asset retirement obligation at end of year	$ 18,058	$ 15,783	$ 17,142

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Activities:
Net income	$ 171,180	$ 155,176	$ 147,334
Non-cash items included in net income:
Depreciation and amortization	265,409	253,142	232,176
Provision for deferred income taxes	(36,837)	(18,231)	11,224
Power and natural gas cost amortizations (deferrals), net	7,122	(78,350)	(51,847)
Amortization of debt expense	2,935	1,974	2,606
Stock-based compensation expense	8,442	8,717	4,713
Equity-related AFUDC	(6,886)	(6,704)	(7,004)
Pension and other postretirement benefit expense	14,283	32,173	29,077
Other regulatory assets and liabilities	(34,189)	(15,129)	4,445
Other non-current assets and liabilities	26,207	(5,280)	(3,769)
Change in decoupling regulatory deferral	(3,328)	33,469	6,056
Realized and unrealized losses (gains) on assets and investments	3,369	(50,006)	(23,187)
Other	(6,066)	11,957	(2,859)
Contributions to defined benefit pension plan	(10,000)	(42,000)	(42,000)
Cash paid on settlement of interest rate swap agreements	(409)	(17,035)	(17,568)
Cash received on settlement of interest rate swap agreements	7,869		324
Changes in certain current assets and liabilities:
Accounts and notes receivable	36,855	(56,007)	(46,107)
Inventory	(52,309)	(22,941)	(17,282)
Collateral posted for derivative instruments	129,226	(141,014)	(17,564)
Income taxes receivable	1,506	(1,125)	20,199
Other current assets	(26,037)	(6,613)	930
Accounts payable	(66,144)	65,928	33,369
Other current liabilities	14,881	22,106	4,074
Net cash provided by operating activities	447,079	124,207	267,340
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(498,637)	(451,995)	(439,939)
Issuance of notes receivable	(3,425)	(2,745)	(1,841)
Equity and property investments	(13,380)	(10,642)	(16,001)
Proceeds from sale of investments	3,200	1,000	8,306
Other	1,853	4,144	4,559
Net cash used in investing activities	(510,389)	(460,238)	(444,916)
Financing Activities:
Net increase (decrease) in short-term borrowings	(114,000)	179,000	81,000
Proceeds from issuance of long-term debt	250,000	399,856	140,000
Maturity of long-term debt and finance leases	(16,735)	(253,085)	(2,935)
Issuance of common stock, net of issuance costs	112,308	137,778	89,998
Cash dividends paid	(140,923)	(129,061)	(118,211)
Other	(5,765)	(7,197)	(4,304)
Net cash provided by financing activities	84,885	327,291	185,548
Net increase (decrease) in cash and cash equivalents	21,575	(8,740)	7,972
Cash and cash equivalents at beginning of year	13,428	22,168	14,196
Cash and cash equivalents at end of year	35,003	13,428	22,168
Cash paid (received) during the year:
Interest	131,522	107,468	98,592
Income taxes paid	2,501	2,251	3,652
Income tax refunds	(800)	(86)	(22,330)
Non-cash financing and investing activities:
Accounts payable for capital expenditures	$ 33,691	$ 27,708	$ 23,938

Pension Plans and Other Postretirement Benefit Plans - Schedule of Fair Value Hierarchy of pension Plan's Assets (Details) - Pension Plan And SERP [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 589,983	$ 540,703	$ 750,963
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,984	5,110
Fixed Income Securities [Member] \| US Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,293	16,732
Fixed Income Securities [Member] \| Domestic Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	175,460	161,180
Fixed Income Securities [Member] \| Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27,052	23,108
Fixed Income Securities [Member] \| Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,772	13,427
Mutual Funds [Member] \| U.S Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	169,993	154,442
Mutual Funds [Member] \| International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	74,749	58,933
Common/Collective Trusts [Member] \| Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25,284	30,406
Partnership And Closely Held Investments [Member] \| International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70,652	69,792
Partnership And Closely Held Investments [Member] \| Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,744	7,573
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	244,742	213,375
Level 1 [Member] \| Mutual Funds [Member] \| U.S Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	169,993	154,442
Level 1 [Member] \| Mutual Funds [Member] \| International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	74,749	58,933
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	242,561	219,557
Level 2 [Member] \| Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,984	5,110
Level 2 [Member] \| Fixed Income Securities [Member] \| US Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19,293	16,732
Level 2 [Member] \| Fixed Income Securities [Member] \| Domestic Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	175,460	161,180
Level 2 [Member] \| Fixed Income Securities [Member] \| Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	27,052	23,108
Level 2 [Member] \| Fixed Income Securities [Member] \| Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 13,772	$ 13,427

Earnings Per Common Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Earnings Per Common Share

NOTE 21. EARNINGS PER COMMON SHARE

The following table presents the computation of basic and diluted earnings per common share for the years ended December 31 (dollars and shares in thousands, except per share amounts):


	2023		2022		2021
Numerator:
Net income	$	171,180	$	155,176	$	147,334
Denominator:
Weighted-average number of common shares outstanding-basic		76,396		72,989		69,951
Effect of dilutive securities:
Performance and restricted stock awards		100		104		134
Weighted-average number of common shares outstanding-diluted		76,495		73,093		70,085
Earnings per common share:
Basic	$	2.24	$	2.13	$	2.11
Diluted	$	2.24	$	2.12	$	2.10

There were no shares excluded from the calculation because they were antidilutive.

Earnings Per Common Share - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share, amount	0	0	0

Short-Term Borrowings - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2023	Apr. 30, 2014
Short-term Debt [Line Items]
Line of credit, outstanding		$ 0
Avista Utilities [Member]
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500,000,000			$ 400,000,000
Line of credit facility, expiration date	2028-06
Line of credit facility additional expiration period	2 years
Line of credit facility, covenant terms, maximum debt to equity ratio	65.00%
Credit agreement amount borrowed			$ 150,000,000
Letters of credit outstanding	$ 4,700,000	35,563,000
Avista Utilities [Member] \| Revolving credit agreement [Member]
Short-term Debt [Line Items]
Line of credit facility, termination date	2023-06
Current borrowings		100,000,000
Avista Utilities [Member] \| 2022 Term Loan [Member]
Short-term Debt [Line Items]
Principal amount		$ 150,000,000
Maturity date		Mar. 30, 2023
Avista Utilities [Member] \| Letter of Credit [Member]
Short-term Debt [Line Items]
Principal amount		$ 50,000,000
Letters of credit outstanding	$ 20,000,000	18,500,000
Alaska Electric Light & Power [Member]
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	$ 25,000,000
Line of credit facility, expiration date	2028-06
Line of credit facility, covenant terms, maximum debt to equity ratio	67.50%
Line of credit, outstanding	$ 0	$ 0

Summary of Significant Accounting Policies - Other Expense (Income) - Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Interest income	$ 5,949	$ 1,957	$ 1,943
Interest on regulatory deferrals	8,713	1,914	1,206
Equity-related AFUDC	6,886	6,704	7,004
Non-service portion of pension and other postretirement benefit expenses	630	3,037	(1,386)
Earnings (losses) on investments	(3,227)	48,492	21,402
Other income	575	613	3,129
Total	$ 19,526	$ 62,717	$ 33,298

Pension Plans and Other Postretirement Benefit Plans - Employer Matching Contributions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits, Description [Abstract]
Employer 401(k) matching contributions	$ 15,022	$ 13,258	$ 11,671

Summary of Significant Accounting Policies - Summary of Effective AFUDC Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Avista Utilities [Member]
Effective Rate On Allowance For Funds Used During Construction [Line Items]
Effective state AFUDC rate	7.03%	7.12%	7.19%
Alaska Electric Light & Power [Member]
Effective Rate On Allowance For Funds Used During Construction [Line Items]
Effective state AFUDC rate	8.61%	8.08%	8.90%

Property, Plant And Equipment

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

NOTE 10. PROPERTY, PLANT AND EQUIPMENT

Net Utility Property

Net utility property consisted of the following as of December 31 (dollars in thousands):


	2023		2022
Utility plant in service	$	7,799,481	$	7,561,688
Construction work in progress		179,527		164,147
Total		7,979,008		7,725,835
Less: Accumulated depreciation and amortization		2,278,952		2,281,126
Total net utility property	$	5,700,056	$	5,444,709

Gross Property, Plant and Equipment

The gross balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in thousands):


	2023		2022
Avista Utilities:
Electric production	$	1,498,398	$	1,593,795
Electric transmission		1,059,389		994,709
Electric distribution		2,383,201		2,236,376
Electric construction work-in-progress (CWIP) and other		394,711		376,981
Electric total		5,335,699		5,201,861
Natural gas underground storage		59,994		58,072
Natural gas distribution		1,539,467		1,452,637
Natural gas CWIP and other		91,492		88,264
Natural gas total		1,690,953		1,598,973
Common plant (including CWIP)		759,498		744,173
Total Avista Utilities		7,786,150		7,545,007
AEL&P:
Electric production		118,817		106,390
Electric transmission		22,827		22,856
Electric distribution		32,322		29,269
Electric CWIP and other		8,552		12,295
Electric total		182,518		170,810
Common plant		10,340		10,018
Total AEL&P		192,858		180,828
Total gross utility property		7,979,008		7,725,835
Other (1)		6,425		16,631
Total	$	7,985,433	$	7,742,466

(1)

Summary of Significant Accounting Policies - Summary of Ratio of Depreciation to Average Depreciable Property and Average Service Lives for Utility Plan in Service (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Avista Utilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Ratio of depreciation to average depreciable property	3.52%	3.50%	3.54%
Avista Utilities [Member] \| Electric Thermal [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	26 years
Avista Utilities [Member] \| Hydroelectric Production [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	79 years
Avista Utilities [Member] \| Electric Transmission [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	50 years
Avista Utilities [Member] \| Electric Distribution [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	40 years
Avista Utilities [Member] \| Natural Gas Distribution [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	44 years
Avista Utilities [Member] \| Other Plant in Service [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	8 years
Alaska Electric Light & Power [Member]
Summary Of Significant Accounting Policies [Line Items]
Ratio of depreciation to average depreciable property	2.78%	2.78%	2.77%
Alaska Electric Light & Power [Member] \| Electric Thermal [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	41 years
Alaska Electric Light & Power [Member] \| Hydroelectric Production [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	42 years
Alaska Electric Light & Power [Member] \| Electric Transmission [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	43 years
Alaska Electric Light & Power [Member] \| Electric Distribution [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	39 years
Alaska Electric Light & Power [Member] \| Other Plant in Service [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	18 years

Revenue (Tables)

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Unbilled Accounts Receivable

Accounts receivable includes unbilled energy revenues of the following amounts as of December 31 (dollars in thousands):


	2023		2022
Unbilled accounts receivable	$	78,531	$	81,691

Schedule of Utilities Operating Revenue Expense Taxes

Utility-related taxes included in revenue from contracts with customers were as follows for the years ended December 31 (dollars in thousands):


	2023		2022		2021
Utility-related taxes	$	75,404	$	69,931	$	62,736

Disaggregation of Revenue

Disaggregation of Total Operating Revenue

The following table disaggregates total operating revenue by segment and source for the years ended December 31 (dollars in thousands):


	2023		2022			2021
Avista Utilities
Revenue from contracts with customers	$	1,485,510	$	1,400,027		$	1,233,904
Derivative revenues		199,133		286,309			152,590
Alternative revenue programs		4,899		(33,357	)		(6,635	)
Deferrals and amortizations for rate refunds to customers		1,026		207			2,984
Other utility revenues		12,289		10,629			10,156
Total Avista Utilities		1,702,857		1,663,815			1,392,999
AEL&P
Revenue from contracts with customers		47,525		45,703			45,051
Deferrals and amortizations for rate refunds to customers		—		(614	)		(190	)
Other utility revenues		614		615			505
Total AEL&P		48,139		45,704			45,366
Other
Revenue from contracts with customers		—		—			2
Other revenues		558		688			569
Total Other		558		688			571
Total operating revenues	$	1,751,554	$	1,710,207		$	1,438,936

Utility Revenue from Contracts with Customers by Type and Service

The following table disaggregates revenue from contracts with customers associated with the Company's electric operations for the years ended December 31 (dollars in thousands):


	2023						2022						2021
	Avista Utilities		AEL&P		Total Utility		Avista Utilities		AEL&P		Total Utility		Avista Utilities		AEL&P		Total Utility
ELECTRIC OPERATIONS
Revenue from contracts with customers
Residential	$	425,258	$	20,232	$	445,490	$	414,823	$	19,667	$	434,490	$	394,717	$	18,940	$	413,657
Commercial and governmental		343,523		27,026		370,549		338,656		25,782		364,438		326,173		25,861		352,034
Industrial		109,689		—		109,689		107,740		—		107,740		106,756		—		106,756
Public street and highway lighting		7,976		267		8,243		7,483		254		7,737		7,472		250		7,722
Total retail revenue		886,446		47,525		933,971		868,702		45,703		914,405		835,118		45,051		880,169
Transmission		32,941		—		32,941		32,307		—		32,307		21,005		—		21,005
Other revenue from contracts with customers		45,332		—		45,332		49,920		—		49,920		33,870		—		33,870
Total revenue from contracts with customers	$	964,719	$	47,525	$	1,012,244	$	950,929	$	45,703	$	996,632	$	889,993	$	45,051	$	935,044

The following table disaggregates revenue from contracts with customers associated with the Company's natural gas operations for the years ended December 31 (dollars in thousands):


	2023		2022		2021
	Avista Utilities		Avista Utilities		Avista Utilities
NATURAL GAS OPERATIONS
Revenue from contracts with customers
Residential	$	325,631	$	284,452	$	221,405
Commercial		164,048		139,923		100,819
Industrial and interruptible		17,315		10,471		7,796
Total retail revenue		506,994		434,846		330,020
Transportation		8,172		8,627		8,547
Other revenue from contracts with customers		5,625		5,625		5,344
Total revenue from contracts with customers	$	520,791	$	449,098	$	343,911

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Allowance as of the beginning of the year

$ 6,473

$ 10,465

$ 11,387

Additions expensed during the year

6,865

149

9,279

Net deductions

^[1]

(8,351)

(4,141)

(10,201)

Allowance as of the end of the year

$ 4,987

$ 6,473

$ 10,465

[1]	The higher balance in 2021 is related to COVID-19 forgiveness program. The Company received support from various government agencies in 2023 and 2022 in the amounts of $1.5 million and $6.1 million, respectively, which were applied to overdue customer accounts.

Balance Sheet Components - Other Property and Investments-Net and Other Non-current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Equity investments	$ 153,350	$ 147,809
Operating lease ROU assets	$ 67,585	$ 68,238
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Total	Total
Finance lease ROU assets	$ 36,414	$ 40,056
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Total	Total
Non-utility property	$ 33,813	$ 25,401
Notes receivable	15,287	17,954
Long-term prepaid license fees	19,448	17,936
Pension assets	32,997	13,382
Investment in affiliated trust	11,547	11,547
Deferred compensation assets	7,794	7,541
Other	15,750	15,221
Total	$ 393,985	$ 365,085

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Summary of Ratio of Depreciation to Average Depreciable Property and Average Service Lives for Utility Plan in Service

For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31:


	2023			2022			2021
Avista Utilities		3.52	%		3.50	%		3.54	%
Alaska Electric Light and Power Company		2.78	%		2.78	%		2.77	%

The average service lives for the following broad categories of utility plant in service are (in years):


	Avista Utilities		Alaska Electric Light and Power Company
Electric thermal/other production		26		41
Hydroelectric production		79		42
Electric transmission		50		43
Electric distribution		40		39
Natural gas distribution property		44	N/A
Other shorter-lived general plant		8		18

The gross balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in thousands):


	2023		2022
Avista Utilities:
Electric production	$	1,498,398	$	1,593,795
Electric transmission		1,059,389		994,709
Electric distribution		2,383,201		2,236,376
Electric construction work-in-progress (CWIP) and other		394,711		376,981
Electric total		5,335,699		5,201,861
Natural gas underground storage		59,994		58,072
Natural gas distribution		1,539,467		1,452,637
Natural gas CWIP and other		91,492		88,264
Natural gas total		1,690,953		1,598,973
Common plant (including CWIP)		759,498		744,173
Total Avista Utilities		7,786,150		7,545,007
AEL&P:
Electric production		118,817		106,390
Electric transmission		22,827		22,856
Electric distribution		32,322		29,269
Electric CWIP and other		8,552		12,295
Electric total		182,518		170,810
Common plant		10,340		10,018
Total AEL&P		192,858		180,828
Total gross utility property		7,979,008		7,725,835
Other (1)		6,425		16,631
Total	$	7,985,433	$	7,742,466

(1)

Summary of Effective AFUDC Rate

The effective AFUDC rate was the following for the years ended December 31:


	2023			2022			2021
Avista Utilities		7.03	%		7.12	%		7.19	%
Alaska Electric Light and Power Company		8.61	%		8.08	%		8.90	%

Stock-Based Compensation


	2023		2022			2021
Stock-based compensation expense	$	7,144	$	7,567		$	4,713
Income tax benefits		1,500		1,589			990
Excess tax benefits (expenses) on settled share-based employee payments		84		(19	)		(909	)


	2023		2022		2021
Restricted Shares
Shares granted during the year		76,806		115,746		62,594
Shares vested during the year		75,007		44,829		34,854
Unvested shares at end of year		152,140		157,860		96,127
Unrecognized compensation expense at end of year (in thousands)	$	3,477	$	3,923	$	2,215
TSR Awards
TSR shares granted during the year		34,912		69,814		64,910
TSR shares vested during the year		61,456		43,730		77,174
TSR shares earned based on market metrics		44,863		48,890		58,652
Unvested TSR shares at end of year		96,915		130,567		107,854
Unrecognized compensation expense at end of year (in thousands)	$	2,235	$	3,533	$	2,653
CEPS Awards
CEPS shares granted during the year		104,685		69,814		64,910
CEPS shares vested during the year		61,456		43,730		38,590
CEPS shares earned based on performance metrics		33,801		—		26,627
Unvested CEPS shares at end of year		161,235		130,567		107,854
Unrecognized compensation expense at end of year (in thousands)	$	2,439	$	2,471	$	1,223

Other Expense (Income) - Net

Other income - net consisted of the following items for the years ended December 31 (dollars in thousands):


	2023			2022		2021
Interest income	$	5,949		$	1,957	$	1,943
Interest on regulatory deferrals		8,713			1,914		1,206
Equity-related AFUDC		6,886			6,704		7,004
Non-service portion of pension and other postretirement benefit expenses		630			3,037		(1,386	)
Earnings (losses) on investments		(3,227	)		48,492		21,402
Other income		575			613		3,129
Total	$	19,526		$	62,717	$	33,298

Allowance for Doubtful Accounts

The following table presents the activity in the allowance for doubtful accounts during the years ended December 31 (dollars in thousands):


	2023			2022			2021
Allowance as of the beginning of the year	$	6,473		$	10,465		$	11,387
Additions expensed during the year		6,865			149			9,279
Net deductions (1)		(8,351	)		(4,141	)		(10,201	)
Allowance as of the end of the year	$	4,987		$	6,473		$	10,465

(1)

Estimated Retirement Costs Collected from Customers

The Company records the amount of estimated retirement costs collected from customers (that do not represent legal or contractual obligations) and includes them as a non-current regulatory liability on the Consolidated Balance Sheets in the following amounts as of December 31 (dollars in thousands):


	2023		2022
Regulatory liability for utility plant retirement costs	$	417,027	$	376,817

Summary of Appropriated Retained Earnings Amount Included in Retained Earnings

The appropriated retained earnings amounts included in retained earnings were as follows as of December 31 (dollars in thousands):


	2023		2022
Appropriated retained earnings	$	59,118	$	57,231

Pension Plans and Other Postretirement Benefit Plans - Change in Benefit Obligation and Plan Assets (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Other current liabilities

$ (14,082)

$ (15,625)

Non-current liabilities

(89,830)

(93,901)

Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans

(357)

(2,058)

Pension Plan And SERP [Member]

557,709

799,042

^[1]

14,350

23,877

$ 25,306

Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]

$ 33,245

$ 26,536

26,160

Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses

Actuarial (gain)/loss

$ 21,373

$ (204,775)

Plan change

3,302

Settlement

(60,206)

Benefits paid

(41,432)

(30,067)

Fair value of plan assets as of beginning of year

585,245

557,709

799,042

540,703

750,963

Actual return on plan assets

78,838

(163,866)

Employer contributions

10,000

42,000

Settlement

(60,206)

Benefits paid

(39,558)

(28,188)

Fair value of plan assets as of end of year

589,983

540,703

750,963

Funded status

4,738

(17,006)

Other non-current assets

32,997

13,382

Other current liabilities

(2,212)

(1,934)

Non-current liabilities

(26,047)

(28,454)

Net amount recognized

4,738

(17,006)

Accumulated pension benefit obligation

514,295

495,654

Unrecognized prior service cost (credit)

3,717

4,105

Unrecognized net actuarial loss

69,002

83,794

Total

72,719

87,899

Less regulatory asset

(71,983)

(85,198)

Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans

$ 736

$ 2,701

Discount rate for benefit obligation

5.86%

6.10%

Discount rate for annual expense

6.10%

3.39%

Expected long-term return on plan assets

8.30%

5.80%

Rate of compensation increase

4.87%

4.69%

$ 115,635

$ 167,598

^[1]

2,394

4,369

4,114

Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]

$ 6,766

$ 5,503

5,139

Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses

Actuarial (gain)/loss

$ 4,799

$ (54,120)

Benefits paid

(7,210)

(7,715)

Fair value of plan assets as of beginning of year

122,384

115,635

167,598

49,472

59,544

Actual return on plan assets

8,654

(10,072)

Fair value of plan assets as of end of year

58,126

49,472

$ 59,544

Funded status

(64,258)

(66,163)

Other current liabilities

(652)

(706)

Non-current liabilities

(63,606)

(65,457)

Net amount recognized

(64,258)

(66,163)

Unrecognized prior service cost (credit)

(1,081)

(1,911)

Unrecognized net actuarial loss

13,103

13,643

Total

12,022

11,732

Less regulatory asset

(12,401)

(12,375)

Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans

$ (379)

$ (643)

Discount rate for benefit obligation

5.83%

6.10%

Discount rate for annual expense

6.10%

3.40%

Expected long-term return on plan assets

7.20%

4.70%

Other Postretirement Benefits [Member] | Pre-Age 65 [Member]

Medical cost trend – initial

6.50%

6.25%

Medical cost trend – ultimate

5.00%

Ultimate medical cost trend year

2030

2028

Other Postretirement Benefits [Member] | Post-Age 65 [Member]

Medical cost trend – initial

6.50%

6.25%

Medical cost trend – ultimate

5.00%

Ultimate medical cost trend year

2030

2028

Other Postretirement Benefits [Member] | Retirees [Member]

$ 61,984

Other Postretirement Benefits [Member] | Fully eligible employees [Member]

68,087

$ 61,984

19,731

Other Postretirement Benefits [Member] | Other participants [Member]

16,054

19,731

33,920

Schedule of Computation of Basic and Diluted Earnings Per Common Share

$ 38,243

$ 33,920

[1]

Revenue - Unbilled Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Unbilled accounts receivable	$ 78,531	$ 81,691

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Fixed lease cost (Other operating expenses)	$ 5,096	$ 4,986	$ 4,970
Variable lease cost (Other operating expenses and Resource costs)	24,628	1,567	1,180
Amortization of ROU asset (Depreciation and amortization)	3,641	3,641	3,641
Interest on lease liabilities (Interest expense)	2,221	2,375	2,522
Operating Lease [Member]
Lessee, Lease, Description [Line Items]
Lease, Cost	29,724	6,553	6,150
Finance Lease [Member]
Lessee, Lease, Description [Line Items]
Lease, Cost	$ 5,862	$ 6,016	$ 6,163

Regulatory Matters - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Regulated Asset Liability [Line Items]
Threshold limit of deadband and sharing bands for future surcharge or rebate to customer		$ 4,000
Threshold to return washington energy recovery mechanism dollars to customers		$ 30,000
Proposed cumulative rebate refund period		2 years
Deferred natural gas costs, asset		$ 51,400	$ 52,100
Forecast [Member]
Regulated Asset Liability [Line Items]
Change in energy recovery mechanism over customer	95.00%
Change in energy recovery mechanism over company sharing basis	5.00%
WASHINGTON
Regulated Asset Liability [Line Items]
Decoupling maximum rate increase request		3.00%
WASHINGTON \| Power Deferrals Regulatory Asset [Member]
Regulated Asset Liability [Line Items]
Regulatory assets		$ 37,600	30,500
IDAHO \| Power Deferrals Regulatory Asset [Member]
Regulated Asset Liability [Line Items]
Regulatory assets		7,600	16,300
Revenue Subject to Refund [Member] \| IDAHO
Regulated Asset Liability [Line Items]
Regulatory liabilities		$ 572	$ 686

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Loss [Abstract]
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $95 and $547, respectively	$ 357	$ 2,058

Energy Purchase Contracts Additional Information (Details)	12 Months Ended
	Dec. 31, 2023
Minimum [Member]
Energy Purchase Contracts [Line Items]
Remaining term of purchase contract	1 month
Maximum [Member]
Energy Purchase Contracts [Line Items]
Remaining term of purchase contract	25 years

Earnings Per Common Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

The following table presents the computation of basic and diluted earnings per common share for the years ended December 31 (dollars and shares in thousands, except per share amounts):


	2023		2022		2021
Numerator:
Net income	$	171,180	$	155,176	$	147,334
Denominator:
Weighted-average number of common shares outstanding-basic		76,396		72,989		69,951
Effect of dilutive securities:
Performance and restricted stock awards		100		104		134
Weighted-average number of common shares outstanding-diluted		76,495		73,093		70,085
Earnings per common share:
Basic	$	2.24	$	2.13	$	2.11
Diluted	$	2.24	$	2.12	$	2.10

Information by Business Segments

12 Months Ended

Dec. 31, 2023

Segment Reporting [Abstract]

Information by Business Segments

NOTE 24. INFORMATION BY BUSINESS SEGMENTS

The business segment presentation reflects the basis used by the Company's management to analyze performance and determine the allocation of resources. The Company's management evaluates performance based on income (loss) from operations before income taxes as well as net income (loss). The accounting policies of the segments are the same as those described in the summary of significant accounting policies. Avista Utilities' business is managed based on the total regulated utility operation; therefore, it is considered one segment. AEL&P is a separate reportable business segment as it has separate financial reports reviewed in detail by the Chief Operating Decision Maker and its operations and risks are sufficiently different from Avista Utilities and the other businesses at AERC that it cannot be aggregated with other operating segments. The Other category, which is not a reportable segment, includes other investments and operations of various subsidiaries, as well as certain other operations of Avista Capital.

The following table presents information for each of the Company’s business segments (dollars in thousands):


	Avista Utilities			Alaska Electric Light and Power Company		Total Utility			Other			Intersegment Eliminations (1)			Total
For the year ended December 31, 2023
Operating revenues	$	1,702,857		$	48,139	$	1,750,996		$	558		$	—		$	1,751,554
Resource costs		698,546			3,826		702,372			—			—			702,372
Other operating expenses		398,523			15,085		413,608			2,760			—			416,368
Depreciation and amortization		254,401			10,928		265,329			80			—			265,409
Income (loss) from operations		242,678			17,294		259,972			(2,282	)		—			257,690
Interest expense (2)		136,924			5,852		142,776			1,881			(1,358	)		143,299
Income tax expense (benefit)		(35,353	)		3,315		(32,038	)		(1,592	)		—			(33,630	)
Net income (loss)		167,016			8,937		175,953			(4,773	)		—			171,180
Capital expenditures (3)		484,716			13,921		498,637			—			—			498,637
For the year ended December 31, 2022
Operating revenues	$	1,663,815		$	45,704	$	1,709,519		$	688		$	—		$	1,710,207
Resource costs		732,298			3,564		735,862			—			—			735,862
Other operating expenses		390,597			14,568		405,165			11,603			—			416,768
Depreciation and amortization		242,198			10,819		253,017			125			—			253,142
Income (loss) from operations		185,582			15,700		201,282			(11,040	)		—			190,242
Interest expense (2)		112,213			5,960		118,173			791			(272	)		118,692
Income tax expense (benefit)		(27,368	)		2,337		(25,031	)		7,840			—			(17,191	)
Net income		117,901			7,545		125,446			29,730			—			155,176
Capital expenditures (3)		443,373			8,622		451,995			834			—			452,829
For the year ended December 31, 2021
Operating revenues	$	1,392,999		$	45,366	$	1,438,365		$	571		$	—		$	1,438,936
Resource costs		493,289			3,834		497,123			—			—			497,123
Other operating expenses		352,241			13,884		366,125			5,927			—			372,052
Depreciation and amortization		221,552			10,363		231,915			261			—			232,176
Income (loss) from operations		217,663			16,186		233,849			(5,617	)		—			228,232
Interest expense (2)		99,629			6,096		105,725			522			(95	)		106,152
Income tax expense		6,029			2,763		8,792			3,239			—			12,031
Net income		125,558			7,224		132,782			14,552			—			147,334
Capital expenditures (3)		435,887			4,052		439,939			1,270			—			441,209
Total Assets:
As of December 31, 2023	$	7,262,704		$	269,683	$	7,532,387		$	191,665		$	(21,575	)	$	7,702,477
As of December 31, 2022		6,976,164			264,322		7,240,486			187,027			(10,163	)		7,417,350
As of December 31, 2021		6,458,244			265,422		6,723,666			132,158			(2,241	)		6,853,583

(1)

Intersegment eliminations reported as interest expense represent intercompany interest. Intersegment eliminations reported as assets represent intersegment accounts receivable.

(2)

Including interest expense to affiliated trusts.

(3)

The capital expenditures for the other businesses are included in other investing activities on the Consolidated Statements of Cash Flows.

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-15

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-40

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//280/tableOfContent

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-26

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-34

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-41

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-21

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-21

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Change in Benefit Obligation and Plan Assets

Pension Plans and Other Postretirement Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2023


	Pension Benefits						Other Post- retirement Benefits
	2023			2022			2023			2022
Change in benefit obligation:
Benefit obligation as of beginning of year	$	557,709		$	799,042		$	115,635		$	167,598
Service cost		14,350			23,877			2,394			4,369
Interest cost		33,245			26,536			6,766			5,503
Actuarial (gain)/loss		21,373			(204,775	)		4,799			(54,120	)
Plan change		—			3,302			—			—
Settlement		—			(60,206	)		—			—
Benefits paid		(41,432	)		(30,067	)		(7,210	)		(7,715	)
Benefit obligation as of end of year	$	585,245		$	557,709		$	122,384		$	115,635
Change in plan assets:
Fair value of plan assets as of beginning of year	$	540,703		$	750,963		$	49,472		$	59,544
Actual return on plan assets		78,838			(163,866	)		8,654			(10,072	)
Employer contributions		10,000			42,000			—			—
Settlement		—			(60,206	)		—			—
Benefits paid		(39,558	)		(28,188	)		—			—
Fair value of plan assets as of end of year	$	589,983		$	540,703		$	58,126		$	49,472
Funded status	$	4,738		$	(17,006	)	$	(64,258	)	$	(66,163	)
Amounts recognized in the Consolidated Balance Sheets:
Other non-current assets	$	32,997		$	13,382		$	—		$	—
Other current liabilities		(2,212	)		(1,934	)		(652	)		(706	)
Non-current liabilities		(26,047	)		(28,454	)		(63,606	)		(65,457	)
Net amount recognized	$	4,738		$	(17,006	)	$	(64,258	)	$	(66,163	)
Accumulated pension benefit obligation	$	514,295		$	495,654
Accumulated postretirement benefit obligation:
For retirees							$	68,087		$	61,984
For fully eligible employees							$	16,054		$	19,731
For other participants							$	38,243		$	33,920
Included in accumulated other comprehensive loss (income) (net of tax):
Unrecognized prior service cost (credit)	$	3,717		$	4,105		$	(1,081	)	$	(1,911	)
Unrecognized net actuarial loss		69,002			83,794			13,103			13,643
Total		72,719			87,899			12,022			11,732
Less regulatory asset		(71,983	)		(85,198	)		(12,401	)		(12,375	)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans	$	736		$	2,701		$	(379	)	$	(643	)


	Pension Benefits						Other Post- retirement Benefits
	2023			2022			2023			2022
Weighted-average assumptions as of December 31:
Discount rate for benefit obligation		5.86	%		6.10	%		5.83	%		6.10	%
Discount rate for annual expense		6.10	%		3.39	%		6.10	%		3.40	%
Expected long-term return on plan assets		8.30	%		5.80	%		7.20	%		4.70	%
Rate of compensation increase		4.87	%		4.69	%
Medical cost trend pre-age 65 – initial								6.50	%		6.25	%
Medical cost trend pre-age 65 – ultimate								5.00	%		5.00	%
Ultimate medical cost trend year pre-age 65							2030			2028
Medical cost trend post-age 65 – initial								6.50	%		6.25	%
Medical cost trend post-age 65 – ultimate								5.00	%		5.00	%
Ultimate medical cost trend year post-age 65							2030			2028

Components of Net Periodic Benefit Cost


	Pension Benefits									Other Post-retirement Benefits
	2023			2022			2021			2023			2022			2021
Components of net periodic benefit cost:
Service cost (1)	$	14,350		$	23,877		$	25,306		$	2,394		$	4,369		$	4,114
Interest cost		33,245			26,536			26,160			6,766			5,503			5,139
Expected return on plan assets		(43,656	)		(43,872	)		(39,088	)		(3,562	)		(2,799	)		(2,400	)
Amortization of prior service cost (credit)		491			257			257			(1,050	)		(1,050	)		(921	)
Net loss recognition		4,915			4,180			6,645			319			3,344			3,865
Settlement loss (2)		—			11,828			—			—			—			—
Net periodic benefit cost	$	9,345		$	22,806		$	19,280		$	4,867		$	9,367		$	9,797

(1)

(2)

The settlement loss was deferred as a regulatory asset and is being amortized over 12 years in accordance with regulatory accounting orders.

Schedule of Allocation of Plan Assets

The target investment allocation percentages by asset classes are indicated in the table below:


	2023			2022
Equity securities		55	%		55	%
Debt securities		40	%		40	%
Real estate		5	%		5	%

Employer Matching Contributions

Employer matching contributions were as follows for the years ended December 31 (dollars in thousands):


	2023		2022		2021
Employer 401(k) matching contributions	$	15,022	$	13,258	$	11,671

Deferred Compensation Assets and Liabilities


	2023		2022
Deferred compensation assets and liabilities	$	7,794	$	7,541

Pension Plan And SERP [Member]

Schedule of Expected Benefit Payments

The Company expects benefit payments under the pension plan and the SERP will total (dollars in thousands):


	2024		2025		2026		2027		2028		Total 2029- 2033
Expected benefit payments	$	41,562	$	42,123	$	42,941	$	43,517	$	44,700	$	232,345

Schedule of Allocation of Plan Assets


	Level 1		Level 2		Level 3		Total
Cash equivalents	$	—	$	6,984	$	—	$	6,984
Fixed income securities:
U.S. government issues		—		19,293		—		19,293
Corporate issues		—		175,460		—		175,460
International issues		—		27,052		—		27,052
Municipal issues		—		13,772		—		13,772
Mutual funds:
U.S. equity securities		169,993		—		—		169,993
International equity securities		74,749		—		—		74,749
Plan assets measured at NAV (not subject to hierarchy disclosure)
Common/collective trusts: real estate		—		—		—		25,284
Partnership/closely held investments:
International equity securities		—		—		—		70,652
Real estate		—		—		—		6,744
Total	$	244,742	$	242,561	$	—	$	589,983


	Level 1		Level 2		Level 3		Total
Cash equivalents	$	—	$	5,110	$	—	$	5,110
Fixed income securities:
U.S. government issues		—		16,732		—		16,732
Corporate issues		—		161,180		—		161,180
International issues		—		23,108		—		23,108
Municipal issues		—		13,427		—		13,427
Mutual funds:
U.S. equity securities		154,442		—		—		154,442
International equity securities		58,933		—		—		58,933
Plan assets measured at NAV (not subject to hierarchy disclosure)
Common/collective trusts: real estate		—		—		—		30,406
Partnership/closely held investments:
International equity securities		—		—		—		69,792
Real estate		—		—		—		7,573
Total	$	213,375	$	219,557	$	—	$	540,703