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Document And Entity Information - shares	3 Months Ended
Document And Entity Information - shares	Mar. 31, 2020	May 01, 2020
Document And Entity Information [Abstract]
Entity Registrant Name	AVISTA CORPORATION
Amendment Flag	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Title of 12(b) Security	Common Stock
Entity Information, Former Legal or Registered Name	None
City Area Code	509
Entity Incorporation, State or Country Code	WA
Document Transition Report	false
Document Quarterly Report	true
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Entity File Number	1-3701
Entity Tax Identification Number	91-0462470
Entity Address, Address Line One	1411 East Mission Avenue
Entity Address, City or Town	Spokane
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	99202-2600
Local Phone Number	489-0500
Trading Symbol	AVA
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Central Index Key	0000104918
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		67,293,360

Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Revenues:
Utility revenues, exclusive of alternative revenue programs	$ 393,820	$ 393,241
Alternative revenue programs	(4,413)	(4,658)
Total utility revenues	389,407	388,583
Non-utility revenues	823	7,898
Total operating revenues	390,230	396,481
Utility operating expenses:
Resource costs	129,547	137,347
Other operating expenses	94,496	83,978
Merger transaction costs	0	19,664
Depreciation and amortization	51,421	48,914
Taxes other than income taxes	30,978	31,943
Other non-utility operating expenses:
Other operating expenses	1,360	7,355
Depreciation and amortization	235	209
Total operating expenses	308,037	329,410
Income from operations	82,193	67,071
Interest expense	26,347	25,651
Interest Expense, Other	270	357
Capitalized interest	(998)	(928)
Merger termination fee	0	(103,000)
Other income-net	(382)	(907)
Income before income taxes	56,956	145,898
Income tax expense	8,532	30,017
Net income	48,424	115,881
Net income attributable to noncontrolling interests	0	(87)
Net income attributable to Avista Corporation shareholders	$ 48,424	$ 115,794
Weighted-average common shares outstanding (thousands), basic	67,239	65,733
Weighted-average common shares outstanding (thousands), diluted	67,381	65,941
Earnings per common share attributable to Avista Corporation shareholders:
Basic	$ 0.72	$ 1.76
Diluted	$ 0.72	$ 1.76

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 48,424	$ 115,881
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	205	160
Total other comprehensive loss	205	160
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	48,629	116,041
Net income attributable to noncontrolling interests	0	(87)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 48,629	$ 115,954

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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+ Details

Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	$ 54	$ 43

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 18,919	$ 9,896
Accounts and notes receivable-less allowances of $4,576 and $2,419, respectively	155,253	166,657
Materials and supplies, fuel stock and stored natural gas	56,681	66,583
Regulatory assets	13,057	21,851
Other current assets	30,328	40,142
Total current assets	274,238	305,129
Net utility property	4,842,318	4,797,007
Goodwill	52,426	52,426
Other regulatory assets	750,866	670,802
Other property and investments-net	254,151	257,092
Total assets	6,173,999	6,082,456
Current Liabilities:
Accounts payable	88,184	110,219
Current portion of long-term debt	52,000	52,000
Short-term borrowings	185,000	185,800
Regulatory liabilities	66,336	51,715
Other current liabilities	174,286	130,979
Total current liabilities	565,806	530,713
Long-term debt	1,843,981	1,843,768
Long-term debt to affiliated trusts	51,547	51,547
Pensions and other postretirement benefits	207,313	212,006
Deferred income taxes	525,217	528,513
Non-current regulatory liabilities	783,376	775,436
Other non-current liabilities and deferred credits	237,664	201,189
Total liabilities	4,214,904	4,143,172
Avista Corporation Stockholders’ Equity:
Common stock, no par value; 200,000,000 shares authorized; 65,668,477 and 65,494,333 shares issued and outstanding as of March 31, 2018 and December 31, 2017, respectively	1,209,312	1,210,741
Accumulated other comprehensive loss	(10,054)	(10,259)
Retained earnings	759,837	738,802
Total Avista Corporation shareholders’ equity	1,959,095	1,939,284
Total equity	1,959,095
Total liabilities and equity	$ 6,173,999	$ 6,082,456

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Accounts and notes receivable, allowances	$ 4,576	$ 2,419
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares outstanding	67,292,233	67,176,996

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities:
Net income	$ 48,424	$ 115,881
Non-cash items included in net income:
Depreciation and amortization	51,421	49,123
Provision for deferred income taxes	(6,765)	8,883
Power and natural gas cost amortizations (deferrals), net	6,380	(48,084)
Amortization of debt expense	653	669
Amortization of investment in exchange power	0	613
Stock-based compensation expense	872	4,845
Equity-related AFUDC	(1,599)	(1,485)
Pension and other postretirement benefit expense	7,952	9,084
Other regulatory assets and liabilities and deferred debits and credits	11,902	1,016
Change in decoupling regulatory deferral	4,155	4,471
Gain on sale of investments	(3,242)	0
Other	5,112	(1,943)
Contributions to defined benefit pension plan	(7,300)	(7,300)
Changes in certain current assets and liabilities:
Accounts and notes receivable	6,078	(9,787)
Materials and supplies, fuel stock and natural gas stored	9,901	(394)
Collateral posted for derivative instruments	(14,283)	3,432
Income taxes receivable	10,500	0
Income taxes payable	4,901	19,360
Other current assets	(2,166)	1,705
Accounts payable	(19,527)	16,697
Other current liabilities	21,905	30,095
Net cash provided by operating activities	135,274	196,881
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(95,525)	(93,615)
Issuance of notes receivable by subsidiaries	(2,779)	(200)
Equity and property investments made by subsidiaries	(1,313)	(3,504)
Proceeds from sale of investments made by subsidiaries	5,148	0
Other	(662)	(345)
Net cash used in investing activities	(95,131)	(97,664)
Financing Activities:
Net decrease in short-term borrowings	(800)	(71,000)
Maturity of long-term debt and finance leases	(700)	(665)
Issuance of common stock	175	190
Cash dividends paid	(27,389)	(25,615)
Other	(2,406)	(896)
Net cash used in financing activities	(31,120)	(97,986)
Net increase in cash and cash equivalents	9,023	1,231
Cash and cash equivalents at beginning of period	9,896	14,656
Cash and cash equivalents at end of period	$ 18,919	$ 14,861

Consolidated Statements Of Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.3875
Beginning Balance (in shares) at Dec. 31, 2018		65,688,356
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued		61,576
Ending Balance (in shares) at Mar. 31, 2019		65,749,932
Beginning Balance at Dec. 31, 2018		$ 1,136,491	$ (7,866)	$ 644,595
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Equity compensation expense		4,452
Issuance of common stock, net of issuance costs		190
Payment of minimum tax withholdings for share-based payment awards		(891)
Other comprehensive income	$ 160		160
Net income attributable to Avista Corporation shareholders	115,794			115,794
Cash dividends paid (common stock)				(25,615)
Ending Balance at Mar. 31, 2019	1,868,222	$ 1,140,242	(7,706)	734,774
Beginning Balance Noncontrolling Interest at Dec. 31, 2018					$ 825
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Net income attributable to noncontrolling interests					87
Ending Balance Noncontrolling Interest at Mar. 31, 2019					912
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Total Avista Corporation shareholders’ equity	1,867,310
Total Avista Corporation shareholders’ equity	$ 1,939,284
Common Stock, Dividends, Per Share, Cash Paid	$ 0.4050
Beginning Balance (in shares) at Dec. 31, 2019	67,176,996	67,176,996
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued		115,237
Ending Balance (in shares) at Mar. 31, 2020	67,292,233	67,292,233
Beginning Balance at Dec. 31, 2019		$ 1,210,741	(10,259)	738,802
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Equity compensation expense		804
Issuance of common stock, net of issuance costs		175
Payment of minimum tax withholdings for share-based payment awards		(2,408)
Other comprehensive income	$ 205		205
Net income attributable to Avista Corporation shareholders	48,424			48,424
Cash dividends paid (common stock)				(27,389)
Ending Balance at Mar. 31, 2020	1,959,095	$ 1,209,312	$ (10,054)	$ 759,837
Beginning Balance Noncontrolling Interest at Dec. 31, 2019					0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Net income attributable to noncontrolling interests					0
Ending Balance Noncontrolling Interest at Mar. 31, 2020					$ 0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Total Avista Corporation shareholders’ equity	$ 1,959,095

Summary Of Significant Accounting Policies	3 Months Ended
Summary Of Significant Accounting Policies	Mar. 31, 2020
Accounting Policies [Abstract]
Summary Of Significant Accounting Policies	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, most of whom are employees who operate the Company's Noxon Rapids generating facility. 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 all of the subsidiary companies in the non-utility businesses, with the exception of AJT Mining Properties, Inc., which is a subsidiary of AERC. See Note 16 for business segment information. See Note 18 for discussion of the sale of METALfx, an unregulated subsidiary of the Company. Basis of Reporting The condensed 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 condensed consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants. Derivative Assets and Liabilities Derivatives are recorded as either assets or liabilities on the Condensed 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 have been concluded to be 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 that are 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 that is determined to be other-than-temporary. 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 cash payments made or received are recorded as a regulatory asset or liability and are subsequently amortized as a component of interest expense over the life of the associated debt. The settled interest rate swap derivatives are also included as a part of Avista Corp.'s cost of debt calculation for ratemaking purposes. The Company has multiple master netting agreements with a variety of entities that allow 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 any 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 Condensed 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, as well as derivatives related to interest rate swaps and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 11 for the Company’s fair value disclosures. 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. See Note 15 for further discussion of the Company's commitments and contingencies. COVID-19 In March 2020, the Company filed an application for authorization to defer certain incremental COVID-19 related costs with the OPUC. In April and May 2020, the Company made similar filings with the IPUC and the WUTC, respectively. In Alaska, a Senate Bill was signed into law that provides for deferral and recovery of incremental COVID-19 related costs subject to approval by the RCA. The recovery of any deferred costs would be determined in future rate making proceedings.

New Accounting Standards	3 Months Ended
New Accounting Standards	Mar. 31, 2020
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Standards	NEW ACCOUNTING STANDARDS ASU No. 2016-12 "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments" On January 1, 2020, the Company adopted ASU 2016-13, which replaces the incurred loss impairment methodology in previous GAAP with a methodology that reflects expected credit losses, and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The Company analyzed its financial instruments within the scope of this guidance, primarily trade receivables, and it did not have a material impact to the Company's financial statements and does not require additional disclosure in these Notes to the Condensed Consolidated Financial Statements. ASU 2018-13 "Fair Value Measurement (Topic 820)" In August 2018, the FASB issued ASU No. 2018-13, which amends the fair value measurement disclosure requirements of ASC 820. The requirements of this ASU include additional disclosure regarding the range and weighted average used to develop significant unobservable inputs for Level 3 fair value estimates and the elimination of certain other previously required disclosures, such as the narrative description of the valuation process for Level 3 fair value measurements. This ASU became effective on January 1, 2020 and the requirements of this ASU did not have a material impact on the Company's fair value disclosures. See Note 11 for the Company's fair value disclosures. ASU No. 2018-14 "Compensation - Retirement Benefits - Defined Benefit Plans - General (Subtopic 715-20)" In August 2018, the FASB issued ASU No. 2018-14, which amends ASC 715 to add, remove and/or clarify certain disclosure requirements related to defined benefit pension and other postretirement plans. The additional disclosure requirements are primarily narrative discussion of significant changes in the benefit obligations and plan assets. The removed disclosures are primarily information about accumulated other comprehensive income expected to be recognized over the next year and the effects of changes associated with assumed health care costs. This ASU is effective for periods beginning after December 15, 2021 and early adoption is permitted. The Company is in the process of evaluating this standard; however, it has determined that it will not early adopt this standard as of March 31, 2020.

Balance Sheet Components Balance Sheet Components (Notes)

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Supplemental Balance Sheet Disclosures [Text Block]

BALANCE SHEET COMPONENTS

Materials and Supplies, Fuel Stock and Stored Natural Gas

Inventories of materials and supplies, fuel stock and stored natural gas are recorded at average cost for our regulated operations and the lower of cost or market for our non-regulated operations and consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Materials and supplies	$	49,007	$	47,402
Fuel stock	4,740		4,875
Stored natural gas	2,934		14,306
Total	$	56,681	$	66,583

Other Current Assets

Other current assets consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$	2,470	$	4,434
Prepayments	22,569		19,652
Income taxes receivable	—		11,047
Other	5,289		5,009
Total	$	30,328	$	40,142

Net Utility Property

Net utility property consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Utility plant in service	$	6,521,033	$	6,462,993
Construction work in progress	189,827		164,941
Total	6,710,860		6,627,934
Less: Accumulated depreciation and amortization	1,868,542		1,830,927
Total net utility property	$	4,842,318	$	4,797,007

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 March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Operating lease ROU assets	$	65,303	$	69,746
Finance lease ROU assets	50,069		50,980
Non-utility property	26,511		27,159
Equity investments	51,467		51,258
Investment in affiliated trust	11,547		11,547
Notes receivable	14,970		14,060
Deferred compensation assets	8,670		8,948
Other	25,614		23,394
Total	$	254,151	$	257,092

Other Current Liabilities

Other current liabilities consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Accrued taxes other than income taxes	$	48,980	$	36,965
Employee paid time off accruals	24,084		22,343
Accrued interest	31,033		16,486
Current portion of pensions and other postretirement benefits	9,811		8,826
Income taxes payable	5,199		298
Derivative liabilities	27,409		10,928
Other current liabilities	27,770		35,133
Total other current liabilities	$	174,286	$	130,979

Other Non-Current Liabilities and Deferred Credits

Other non-current liabilities and deferred credits consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Operating lease liabilities	$	62,145	$	65,565
Finance lease liabilities	51,016		51,750
Deferred investment tax credits	30,588		30,444
Asset retirement obligations	20,263		20,338
Derivative liabilities	60,278		19,685
Other	13,374		13,407
Total	$	237,664	$	201,189

Regulatory Assets and Liabilities

Regulatory assets and liabilities consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31, 2020				December 31, 2019
	Current		Non-Current		Current		Non-Current
Regulatory Assets
Energy commodity derivatives	$	78	$	—	$	6,310	$	264
Decoupling surcharge	10,927		15,504		12,098		14,806
Pension and other postretirement benefit plans	—		206,112		—		208,754
Interest rate swaps	—		246,566		—		168,594
Deferred income taxes	—		96,525		—		95,752
Settlement with Coeur d'Alene Tribe	—		41,005		—		41,332
AFUDC above FERC allowed rate	—		41,333		—		40,749
Demand side management programs	—		8,670		—		12,170
Utility plant to be abandoned	—		31,678		—		31,291
Other regulatory assets	2,052		63,473		3,443		57,090
Total regulatory assets	$	13,057	$	750,866	$	21,851	$	670,802



	March 31, 2020				December 31, 2019
	Current		Non-Current		Current		Non-Current
Regulatory Liabilities
Income tax related liabilities	$	23,975	$	404,046	$	23,803	$	407,549
Deferred natural gas costs	5,449		—		3,189		—
Deferral power costs	23,595		20,716		14,155		23,544
Decoupling rebate	363		5,972		255		2,398
Provision for rate refund (Washington remand case)	8,490		—		3,565		—
Utility plant retirement costs	—		317,203		—		312,403
Interest rate swaps	—		16,136		—		17,088
Other regulatory liabilities	4,464		19,303		6,748		12,454
Total regulatory liabilities	$	66,336	$	783,376	$	51,715	$	775,436

Revenue Revenue (Notes)

3 Months Ended

Mar. 31, 2020

Revenue from Contract with Customer [Abstract]

Revenue from Contract with Customer [Text Block]

REVENUE

ASC 606 defines 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. Given that all revenue recognition criteria are met upon the delivery of energy to customers, revenue is recognized immediately at that time.

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

Non-Derivative Wholesale Contracts

The Company has certain wholesale contracts which are not accounted for as derivatives and, accordingly, are within the scope of ASC 606 and considered revenue from contracts with customers. Revenue is recognized as energy is delivered to the customer or the service is available for a 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 that alternative revenue programs are contracts between an entity and a regulator of utilities, not a contract between an entity and a customer. GAAP requires that an entity present revenue arising from alternative revenue programs separately from revenues arising from contracts with customers on the face of the Condensed 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 Condensed 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 that will be surcharged or rebated to customers in future periods. GAAP requires that for any 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 current period Condensed Consolidated Statement of Income. Any 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 that must be 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.

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 specifically scoped out of ASC 606. As such, these revenues 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 those transactions that are entered into and settled within the same month.

Other Utility Revenue

Other utility revenue includes rent, revenues from the lineman training school, sales of materials, late fees and other charges that do not represent contracts with customers. Other utility revenue also includes the provision for earnings sharing and the deferral and amortization of refunds to customers associated with the TCJA. This revenue is scoped out of ASC 606, 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 that are “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 taxes that are imposed on Avista Utilities as opposed to being imposed on its 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 that were included in revenue from contracts with customers were as follows for the three months ended March 31 (dollars in thousands):



	2020		2019
Utility-related taxes	$	18,700	$	19,089

Non-Utility Revenues

Revenue from Contracts with Customers

Non-utility revenue from contracts with customers is derived from contracts with one performance obligation. Prior to its sale in April 2019 (See Note 18 for further discussion on the sale of METALfx), METALfx had one performance obligation, the delivery of a product, and revenues were recognized when the risk of loss transferred to the customer, which occurred when products were shipped. The Steam Plant Brew Pub serves food and beverages to customers, its one performance obligation, and recognizes revenues at the time of service to the customer.

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 does have one capacity agreement where the customer makes payments throughout the year and depending on the timing of the customer payments, it can result in an immaterial amount of deferred revenue or a receivable from the customer. As of March 31, 2020, the Company estimates it had unsatisfied capacity performance obligations of $4.7 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 three months ended March 31 (dollars in thousands):



	2020			2019
Avista Utilities
Revenue from contracts with customers	$	351,628		$	354,301
Derivative revenues	31,075			24,127
Alternative revenue programs	(4,413		)	(4,658		)
Deferrals and amortizations for rate refunds to customers	(2,606		)	2,135
Other utility revenues	1,521			1,797
Total Avista Utilities	377,205			377,702
AEL&P
Revenue from contracts with customers	12,126			10,736
Deferrals and amortizations for rate refunds to customers	(48		)	(48		)
Other utility revenues	124			193
Total AEL&P	12,202			10,881
Other
Revenue from contracts with customers	514			7,647
Other revenues	309			251
Total other	823			7,898
Total operating revenues	$	390,230		$	396,481

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 three months ended March 31 (dollars in thousands):



	2020						2019
	Avista Utilities		AEL&P		Total Utility		Avista Utilities		AEL&P		Total Utility
ELECTRIC OPERATIONS
Revenue from contracts with customers
Residential	$	107,977	$	5,866	$	113,843	$	115,392	$	5,852	$	121,244
Commercial and governmental	78,849		6,199		85,048		79,245		4,821		84,066
Industrial	24,711		—		24,711		25,248		—		25,248
Public street and highway lighting	1,783		61		1,844		1,903		63		1,966
Total retail revenue	213,320		12,126		225,446		221,788		10,736		232,524
Transmission	3,774		—		3,774		5,152		—		5,152
Other revenue from contracts with customers	5,289		—		5,289		8,194		—		8,194
Total revenue from contracts with customers	$	222,383	$	12,126	$	234,509	$	235,134	$	10,736	$	245,870

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



	2020		2019
	Avista Utilities		Avista Utilities
NATURAL GAS OPERATIONS
Revenue from contracts with customers
Residential	$	84,173	$	77,336
Commercial	39,401		36,595
Industrial and interruptible	2,194		1,627
Total retail revenue	125,768		115,558
Transportation	2,352		2,484
Other revenue from contracts with customers	1,125		1,125
Total revenue from contracts with customers	$	129,245	$	119,167

Derivatives And Risk Management

3 Months Ended

Mar. 31, 2020

Derivative Instruments and Hedges, Assets [Abstract]

Derivatives And Risk Management

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, in order 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. On the basis of 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 helps mitigate 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 March 31, 2020 that are 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
Remainder 2020	3	395	10,232	61,330	366	1,491	871	27,035
2021	—	123	305	32,120	—	246	1,490	21,700
2022	—	—	450	7,820	—	—	—	2,700

As of March 31, 2020, there are no expected deliveries of energy commodity derivatives after 2022.

The following table presents the underlying energy commodity derivative volumes as of December 31, 2019 that are 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
2020	2	442	9,813	78,803	133	1,724	2,984	37,848
2021	—	—	153	25,523	—	246	1,040	13,108
2022	—	—	225	4,725	—	—	—	675

As of December 31, 2019, there are no expected deliveries of energy commodity derivatives after 2022.


(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.

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 collected 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 that Avista Corp. has outstanding as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Number of contracts	23		20
Notional amount (in United States dollars)	$	5,219	$	5,932
Notional amount (in Canadian dollars)	7,247		7,828

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. hedges a portion of its interest rate risk with financial derivative instruments, which may include interest rate swap

derivatives and U.S. Treasury lock agreements. These interest rate swap derivatives and U.S. Treasury lock agreements 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 that Avista Corp. has outstanding as of March 31, 2020 and December 31, 2019 (dollars in thousands):



Balance Sheet Date	Number of Contracts	Notional Amount		Mandatory Cash Settlement Date
March 31, 2020	7	$	70,000	2020
	4	45,000		2021
	11	120,000		2022
	1	10,000		2023
December 31, 2019	7	70,000		2020
	3	35,000		2021
	10	110,000		2022

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 Condensed Consolidated Balance Sheet as of March 31, 2020 and December 31, 2019 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 Condensed Consolidated Balance Sheet as of March 31, 2020 (in thousands):



	Fair Value
Derivative and Balance Sheet Location	Gross Asset		Gross Liability			Collateral Netted			Net Asset (Liability) on Balance Sheet
Foreign currency exchange derivatives
Other current liabilities	$	36	$	(103	)	$	—		$	(67	)
Interest rate swap derivatives
Other current liabilities	—		(32,967		)	12,967			(20,000		)
Other non-current liabilities and deferred credits	—		(79,271		)	14,123			(65,148		)
Energy commodity derivatives
Other current assets	28,964		(26,503		)	(695		)	1,766
Other property and investments-net and other non-current assets	6,072		(3,626		)	—			2,446
Other current liabilities	51		(2,590		)	—			(2,539		)
Other non-current liabilities and deferred credits	—		(24		)	—			(24		)
Total derivative instruments recorded on the balance sheet	$	35,123	$	(145,084	)	$	26,395		$	(83,566	)

The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2019 (in thousands):



	Fair Value
Derivative and Balance Sheet Location	Gross Asset		Gross Liability			Collateral Netted		Net Asset (Liability) on Balance Sheet
Foreign currency exchange derivatives
Other current assets	$	97	$	—		$	—	$	97
Interest rate swap derivatives
Other current assets	589		—			—		589
Other current liabilities	238		(9,379		)	1,316		(7,825		)
Other non-current liabilities and deferred credits	725		(24,677		)	5,454		(18,498		)
Energy commodity derivatives
Other current assets	416		(245		)	—		171
Other property and investments-net and other non-current assets	6,369		(5,446		)	—		923
Other current liabilities	34,760		(41,241		)	3,378		(3,103		)
Other non-current liabilities and deferred credits	28		(1,215		)	—		(1,187		)
Total derivative instruments recorded on the balance sheet	$	43,222	$	(82,203	)	$	10,148	$	(28,833	)

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 a downgrade in Avista Corp.'s credit ratings or changes in market prices, 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 Avista Corp.'s collateral outstanding related to its derivative instruments as of March 31, 2020 and December 31, 2019 (in thousands):



	March 31,			December 31,
	2020			2019
Energy commodity derivatives
Cash collateral posted	$	1,775		$	7,812
Letters of credit outstanding	25,000			17,400
Balance sheet offsetting (cash collateral against net derivative positions)	(695		)	3,378

Interest rate swap derivatives
Cash collateral posted	27,090			6,770
Letters of credit outstanding	3,910			—
Balance sheet offsetting (cash collateral against net derivative positions)	27,090			6,770

Certain of Avista Corp.’s derivative instruments contain provisions that require 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 that are in a liability position and the amount of additional collateral Avista Corp. could be required to post as of March 31, 2020 and December 31, 2019 (in thousands):



	March 31,		December 31,
	2020		2019
Energy commodity derivatives
Liabilities with credit-risk-related contingent features	$	1	$	814
Additional collateral to post	1		814

Interest rate swap derivatives
Liabilities with credit-risk-related contingent features	112,238		34,056
Additional collateral to post	81,280		26,912

Pension Plans And Other Postretirement Benefit Plans

3 Months Ended

Mar. 31, 2020

Retirement Benefits, Description [Abstract]

Pension Plans and Other Postretirement Benefit Plans

PENSION PLANS AND OTHER POSTRETIREMENT BENEFIT PLANS

Avista Utilities

Avista Utilities’ maintained the same pension and other postretirement plans during the three months ended March 31, 2020 as those described as of December 31, 2019. The Company’s funding policy is to contribute at least the minimum amounts that are required to be funded under the Employee Retirement Income Security Act, but not more than the maximum amounts that are currently deductible for income tax purposes. The Company contributed $7.3 million in cash to the pension plan for the three months ended March 31, 2020 and it expects to contribute a total of $22 million in 2020.

The Company uses a December 31 measurement date for its defined benefit pension and other postretirement benefit plans. The following table sets forth the components of net periodic benefit costs for the three months ended March 31 (dollars in thousands):



	Pension Benefits						Other Postretirement Benefits
	2020			2019			2020			2019
Service cost	$	5,546		$	4,874		$	979		$	772
Interest cost	6,971			7,138			1,515			1,372
Expected return on plan assets	(9,125		)	(7,815		)	(630		)	(718		)
Amortization of prior service cost	75			75			(275		)	(275		)
Net loss recognition	1,654			2,415			1,243			1,246
Net periodic benefit cost	$	5,121		$	6,687		$	2,832		$	2,397

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.

The non-service portion of costs in the table above are recorded to other expense below income from operations in the Condensed Consolidated Statements of Income or capitalized as a regulatory asset. Approximately 40 percent of the costs are capitalized to regulatory assets and 60 percent is expensed to the income statement.

Income Taxes Income Taxes (Notes)

3 Months Ended

Mar. 31, 2020

Income Tax Disclosure [Abstract]

Income Tax Disclosure [Text Block]

INCOME TAXES

The following table summarizes the significant factors impacting the difference between our effective tax rate and the federal statutory rate for the three months ended March 31 (dollars in thousands):



	2020					2019
Federal income taxes at statutory rates	$	11,961		21.0	%	$	30,639		21.0	%
Increase (decrease) in tax resulting from:
Tax effect of regulatory treatment of utility plant differences	(2,402		)	(4.2	)	(2,080		)	(1.4	)
State income tax expense	1,227			2.1		1,659			1.1
Acquisition costs	—			—		(1,824		)	(1.2	)
Settlement of equity awards	165			0.3		612			0.4
Other	(2,419		)	(4.2	)	1,011			0.7
Total income tax expense	$	8,532		15.0	%	$	30,017		20.6	%

Committed Lines of Credit

3 Months Ended

Mar. 31, 2020

Short-term Debt [Abstract]

Committed Lines of Credit

COMMITTED LINES OF CREDIT

Avista Corp.

Avista Corp. has a committed line of credit with various financial institutions in the total amount of $400.0 million. The Company expects to amend and extend the revolving line of credit agreement in the second quarter for a revised term of one additional year beyond the current maturity date of April 2021, with the option to extend for an additional one year period. 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 March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,			December 31,
	2020			2019
Balance outstanding at end of period	$	185,000		$	182,300
Letters of credit outstanding at end of period	$	32,983		$	21,473
Average interest rate at end of period	1.66		%	2.64		%

As of March 31, 2020 and December 31, 2019, the borrowings outstanding under Avista Corp.'s committed line of credit were

classified as short-term borrowings on the Condensed Consolidated Balance Sheet.

AEL&P

AEL&P has a committed line of credit in the amount of $25.0 million that expires in November 2024. As of March 31, 2020 and December 31, 2019, there were borrowings of $0 and $3.5 million, respectively, and there were no letters of credit outstanding under this committed line of credit. 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.

CREDIT AGREEMENT

Credit Agreement

On April 6, 2020, the Company entered into a Credit Agreement with U.S. Bank National Association, as Lender and Administrative Agent, and CoBank, ACB, as Lender in the amount of $100 million at an interest rate of 1-Month LIBOR plus 125 basis points with a maturity date of April 5, 2021. Loans under this agreement are unsecured and have a variable annual interest rate determined by either the Eurodollar rate or the Alternative Base Rate depending on the type of loan selected by Avista Corp.

The Credit Agreement contains customary covenants and default provisions, including a covenant not to permit the ratio of "consolidated total debt" to "consolidated total capitalization" of Avista Corp. to be greater than 65 percent at any time.

The Company has borrowed the entire $100 million available under this agreement, which is being used to provide additional liquidity. The amount can be repaid early; however, the amount repaid cannot be re-borrowed.

Credit Agreement Credit Agreement (Notes)

3 Months Ended

Mar. 31, 2020

Credit Agreement [Abstract]

Short-term Debt [Text Block]

COMMITTED LINES OF CREDIT

Avista Corp.



	March 31,			December 31,
	2020			2019
Balance outstanding at end of period	$	185,000		$	182,300
Letters of credit outstanding at end of period	$	32,983		$	21,473
Average interest rate at end of period	1.66		%	2.64		%

As of March 31, 2020 and December 31, 2019, the borrowings outstanding under Avista Corp.'s committed line of credit were

classified as short-term borrowings on the Condensed Consolidated Balance Sheet.

AEL&P

CREDIT AGREEMENT

Credit Agreement

Long- Term Debt to Affiliated Trust Long-Term Debt to Affiliated Trust (Notes)

3 Months Ended

Mar. 31, 2020

Long-Term Debt to Affiliated Trust [Abstract]

Long Term Debt To Affiliated Trusts Disclosure [Text Block]

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.

The distribution rates paid were as follows during the three months ended March 31, 2020 and the year ended December 31, 2019:



	March 31,		December 31,
	2020		2019
Low distribution rate	2.46	%	2.79	%
High distribution rate	2.79	%	3.61	%
Distribution rate at the end of the period	2.46	%	2.79	%

Concurrent with the issuance of the Preferred Trust Securities, Avista Capital II issued $1.5 million of Common Trust Securities to the Company. The 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 that 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 Condensed Consolidated Balance Sheets. Interest expense to affiliated trusts in the Condensed Consolidated Statements of Income represents interest expense on these debentures.

Fair Value

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value

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 and material capital leases) and long-term debt to affiliated trusts are reported at carrying value on the Condensed 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 measurement) and the lowest priority to fair values derived from unobservable inputs (Level 3 measurement).

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 those financial instruments that are 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 that are 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 Condensed Consolidated Balance Sheets as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31, 2020				December 31, 2019
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Long-term debt (Level 2)	$	963,500	$	1,107,956	$	963,500	$	1,124,649
Long-term debt (Level 3)	947,000		949,144		947,000		1,048,440
Snettisham finance lease obligation (Level 3)	53,850		56,900		54,550		58,000
Long-term debt to affiliated trusts (Level 3)	51,547		33,506		51,547		41,238

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 65.00 to 133.98, where a par value of 100.0 represents the carrying value recorded on the Condensed 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 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 capital lease obligation, the estimated fair value of these items was determined based on a discounted cash flow model using available market information. The Snettisham capital lease obligation was discounted to present value using the Morgan Markets A Ex-Fin discount rate as published on March 31, 2020.

The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Condensed Consolidated Balance Sheets as of March 31, 2020 and December 31, 2019 at fair value on a recurring basis (dollars in thousands):



	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
March 31, 2020
Assets:
Energy commodity derivatives	$	—	$	35,061	$	—	$	(30,849	)	$	4,212
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		26		(26		)	—
Foreign currency exchange derivatives	—		36		—		(36		)	—
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	2,642		—		—		—			2,642
Equity securities (2)	5,585		—		—		—			5,585
Total	$	8,227	$	35,097	$	26	$	(30,911	)	$	12,439
Liabilities:
Energy commodity derivatives	$	—	$	30,464	$	—	$	(30,154	)	$	310
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		2,279		(26		)	2,253
Foreign currency exchange derivatives	—		103		—		(36		)	67
Interest rate swap derivatives	—		112,238		—		(27,090		)	85,148
Total	$	—	$	142,805	$	2,279	$	(57,306	)	$	87,778



	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2019
Assets:
Energy commodity derivatives	$	—	$	41,546	$	—	$	(40,452	)	$	1,094
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		27		(27		)	—
Foreign currency exchange derivatives	—		97		—		—			97
Interest rate swap derivatives	—		1,552		—		(963		)	589
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	2,232		—		—		—			2,232
Equity securities (2)	6,271		—		—		—			6,271
Total	$	8,503	$	43,195	$	27	$	(41,442	)	$	10,283
Liabilities:
Energy commodity derivatives	$	—	$	45,144	$	—	$	(43,830	)	$	1,314
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		3,003		(27		)	2,976
Interest rate swap derivatives	—		34,056		—		(7,733		)	26,323
Total	$	—	$	79,200	$	3,003	$	(51,590	)	$	30,613


(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 any 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 Condensed 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 Condensed Consolidated Balance Sheets is due to netting arrangements with certain counterparties. See Note 5 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 US 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. The balance disclosed in the table above excludes cash and cash equivalents of $0.4 million as of March 31, 2020 and December 31, 2019.

Level 3 Fair Value

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 March 31, 2020 (dollars in thousands):



	Fair Value (Net) at
	March 31, 2020			Valuation Technique	Unobservable Input	Range and Weighted Average Price
Natural gas exchange agreement	$	(2,253	)	Internally derived weighted average cost of gas	Forward purchase prices	$1.16 - $1.80/mmBTU $1.47 Weighted Average
					Forward purchase prices	$1.16 - $1.80/mmBTU $1.47 Weighted Average
					Forward sales prices	$1.33 - $3.79/mmBTU $2.96 Weighted Average
					Purchase volumes	155,000 - 310,000 mmBTUs
					Sales volumes	60,000 - 310,000 mmBTUs

The following table presents activity for energy commodity derivative assets (liabilities) measured at fair value using significant unobservable inputs (Level 3) for the three months ended March 31 (dollars in thousands):



	Natural Gas Exchange Agreement			Power Exchange Agreement			Total
Three months ended March 31, 2020:
Balance as of January 1, 2020	$	(2,976	)	$	—		$	(2,976	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	485			—			485
Settlements	238			—			238
Ending balance as of March 31, 2020 (2)	$	(2,253	)	$	—		$	(2,253	)
Three months ended March 31, 2019:
Balance as of January 1, 2019	$	(2,774	)	$	(2,488	)	$	(5,262	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	8,977			(1,018		)	7,959
Settlements	(8,307		)	2,894			(5,413		)
Ending balance as of March 31, 2019 (2)	$	(2,104	)	$	(612	)	$	(2,716	)


(1)	All gains and losses are included in other regulatory assets and liabilities. There were no gains and losses included in either net income or other comprehensive income during any of the periods presented in the table above.

(2)

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

- Definition

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.

+ References + Details

Common Stock Common Stock (Notes)

3 Months Ended

Mar. 31, 2020

Stockholders' Equity Note [Abstract]

Stockholders' Equity Note Disclosure [Text Block]

COMMON STOCK

The Company had entered into four separate sales agency agreements under which the sales agents offered and sold new shares of the Company’s common stock from time to time. During the three months ended March 31, 2020 the Company did not issue shares under the sales agency agreements. These sales agency agreements expired on February 29, 2020. The Company is currently working on entering into new sales agency agreements.

ACCUMULATED OTHER COMPREHENSIVE LOSS

Accumulated other comprehensive loss, net of tax, consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $2,673 and $2,727, respectively	$	10,054	$	10,259

The following table details the reclassifications out of accumulated other comprehensive loss to net income by component for the three months ended March 31 (dollars in thousands).



	Amounts Reclassified from Accumulated Other Comprehensive Loss
Details about Accumulated Other Comprehensive Loss Components	2020			2019			Affected Line Item in Statement of Income
Amortization of defined benefit pension items
Amortization of net prior service cost	$	(200	)	$	(200	)	(a)
Amortization of net loss	3,100			3,661			(a)
Adjustment due to effects of regulation	(2,641		)	(3,258		)	(a)
	259			203			Total before tax
	(54		)	(43		)	Tax expense
	$	205		$	160		Net of tax

(a)

These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 6 for additional details).

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss (Notes)

3 Months Ended

Mar. 31, 2020

Accumulated Other Comprehensive Loss [Abstract]

Stockholders' Equity Note Disclosure [Text Block]

COMMON STOCK

ACCUMULATED OTHER COMPREHENSIVE LOSS

Accumulated other comprehensive loss, net of tax, consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $2,673 and $2,727, respectively	$	10,054	$	10,259

The following table details the reclassifications out of accumulated other comprehensive loss to net income by component for the three months ended March 31 (dollars in thousands).



	Amounts Reclassified from Accumulated Other Comprehensive Loss
Details about Accumulated Other Comprehensive Loss Components	2020			2019			Affected Line Item in Statement of Income
Amortization of defined benefit pension items
Amortization of net prior service cost	$	(200	)	$	(200	)	(a)
Amortization of net loss	3,100			3,661			(a)
Adjustment due to effects of regulation	(2,641		)	(3,258		)	(a)
	259			203			Total before tax
	(54		)	(43		)	Tax expense
	$	205		$	160		Net of tax

(a)

These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 6 for additional details).

Earnings Per Common Share Attributable To Avista Corporation

3 Months Ended

Mar. 31, 2020

Earnings Per Share [Abstract]

Earnings Per Common Share Attributable To Avista Corporation Shareholders

EARNINGS PER COMMON SHARE ATTRIBUTABLE TO AVISTA CORP. SHAREHOLDERS

The following table presents the computation of basic and diluted earnings per common share attributable to Avista Corp. shareholders for the three months ended March 31 (in thousands, except per share amounts):



	2020		2019
Numerator:
Net income attributable to Avista Corp. shareholders	$	48,424	$	115,794
Denominator:
Weighted-average number of common shares outstanding-basic	67,239		65,733
Effect of dilutive securities:
Performance and restricted stock awards	142		208
Weighted-average number of common shares outstanding-diluted	67,381		65,941
Earnings per common share attributable to Avista Corp. shareholders:
Basic	$	0.72	$	1.76
Diluted	$	0.72	$	1.76

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

Commitments And Contingencies	3 Months Ended
Commitments And Contingencies	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	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 intends to vigorously protect and defend its interests and pursue its rights. However, no assurance can be given as to the ultimate outcome of any particular matter because litigation and other contested proceedings are inherently subject to numerous uncertainties. For matters that affect Avista Utilities’ or AEL&P's operations, the Company intends to seek, to the extent appropriate, recovery of incurred costs through the ratemaking process. 2015 Washington General Rate Cases In January 2016, the Company received an order (Order 05) that concluded its electric and natural gas general rate cases that were originally filed with the WUTC in February 2015. New electric and natural gas rates were effective on January 11, 2016. PC Petition for Judicial Review In March 2016, Public Counsel (PC) filed in Thurston County Superior Court a Petition for Judicial Review of the WUTC's Order 05 and Order 06. In April 2016, this matter was certified for review directly by the Court of Appeals, an intermediate appellate court in the State of Washington. On August 7, 2018, the Court of Appeals issued a "Published Opinion" (Opinion) which concluded that the WUTC's use of an attrition allowance to calculate Avista Corp.'s rate base violated Washington law. In the Opinion, the Court stated that because the projected additions to rate base in the future were not "used and useful" for service at the time the request for the rate increase was made, they may not lawfully be included in the Company's rate base to justify a rate increase. Accordingly, the Court concluded that the WUTC erred in including an attrition allowance in the calculation of Avista Corp.’s electric and natural gas rate base. The Court noted, however, that the law does not prohibit an attrition allowance in the calculation, for ratemaking purposes, of recoverable operating and maintenance expense. Since the WUTC order provided one lump sum attrition allowance without distinguishing what portion was for rate base and which was for operating and maintenance expenses or other considerations, the Court struck all portions of the attrition allowance attributable to Avista Corp.'s rate base and reversed and remanded the case for the WUTC to recalculate Avista Corp.’s rates without including an attrition allowance in the calculation of rate base. On March 6, 2020, the Company received an order from the WUTC that will require it to refund $8.5 million to electric and natural gas customers. The Company will refund $4.9 million to electric customers and $3.6 million to natural gas customers. The Company previously recorded a customer refund liability of $3.6 million in 2019. Boyds Fire (State of Washington Department of Natural Resources v. Avista) On August 19, 2019, the Company was served with a complaint filed by the State of Washington Department of Natural Resources, seeking recovery of fire suppression costs and related expenses incurred in connection with a wildfire that occurred in Ferry County, Washington in August 2018. Specifically, the complaint alleges that 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. was negligent in failing to identify and remove it before the tree came into contact with the line. Avista Corp. disputes that the tree in question was the cause of the fire and that it was negligent in failing to identify and remove it. The case is in the early stages of discovery and the plaintiff has not yet provided a statement specifying damages. Because the resolution of this claim remains uncertain, legal counsel cannot express an opinion on the extent, if any, of the Company’s liability, nor is it possible for the Company to estimate the impact of any outcome at this time. The Company intends to vigorously defend itself in the litigation. Other Contingencies In the normal course of business, the Company has various other legal claims and contingent matters outstanding. The Company believes that 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 that 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. See "Note 21 of the Notes to Consolidated Financial Statements" in the 2019 Form 10-K for additional discussion regarding other contingencies.

Information By Business Segments

3 Months Ended

Mar. 31, 2020

Segment Reporting [Abstract]

Information by Business Segments

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) attributable to Avista Corp. shareholders. 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 that are 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 any 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 three months ended March 31, 2020:
Operating revenues	$	377,205	$	12,202		$	389,407	$	823		$	—		$	390,230
Resource costs	129,557		(10		)	129,547		—			—			129,547
Other operating expenses	91,279		3,217			94,496		1,360			—			95,856
Depreciation and amortization	48,974		2,447			51,421		235			—			51,656
Income (loss) from operations	76,534		6,246			82,780		(587		)	—			82,193
Interest expense (3)	24,983		1,589			26,572		131			(86		)	26,617
Income taxes	7,404		1,301			8,705		(173		)	—			8,532
Net income (loss) attributable to Avista Corp. shareholders	45,979		3,395			49,374		(950		)	—			48,424
Capital expenditures (4)	94,056		1,470			95,526		109			—			95,635
For the three months ended March 31, 2019:
Operating revenues	$	377,702	$	10,881		$	388,583	$	7,898		$	—		$	396,481
Resource costs	138,712		(1,365		)	137,347		—			—			137,347
Other operating expenses (2)	100,583		3,059			103,642		7,355			—			110,997
Depreciation and amortization	46,507		2,407			48,914		209			—			49,123
Income from operations	60,224		6,513			66,737		334			—			67,071
Interest expense (3)	24,264		1,596			25,860		588			(440		)	26,008
Income taxes	28,544		1,363			29,907		110			—			30,017
Net income attributable to Avista Corp. shareholders	111,901		3,552			115,453		341			—			115,794
Capital expenditures (4)	92,309		1,306			93,615		162			—			93,777
Total Assets:
As of March 31, 2020:	$	5,808,619	$	272,178		$	6,080,797	$	112,213		$	(19,011	)	$	6,173,999
As of December 31, 2019:	$	5,713,268	$	271,393		$	5,984,661	$	113,390		$	(15,595	)	$	6,082,456


(1)	Intersegment eliminations reported as interest expense represent intercompany interest.


(2)	Other operating expenses for Avista Utilities for the three months ended March 31, 2019 include merger transaction costs which are separately disclosed on the Condensed Consolidated Statements of Income.


(3)	Including interest expense to affiliated trusts.

(4)

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

Termination of Proposed Acquisition by Hydro One Termination of Proposed Acquisition by Hydro One (Notes)	3 Months Ended
	Mar. 31, 2020
Business Acquisition [Line Items]
Business Combination Disclosure [Text Block]	On July 19, 2017, Avista Corp. entered into a Merger Agreement that provided for Avista Corp. to become an indirect, wholly-owned subsidiary of Hydro One, subject to the satisfaction or waiver of specified closing conditions, including approval by regulatory agencies. Hydro One, based in Toronto, is Ontario’s largest electricity transmission and distribution provider. Termination of the Merger Agreement Due to the denial of the proposed merger by certain of the Company's regulatory commissions, on January 23, 2019, Avista Corp., Hydro One and certain subsidiaries thereof, entered into a Termination Agreement indicating their mutual agreement to terminate the Merger Agreement, effective immediately. Pursuant to the terms of the Termination Agreement, Hydro One paid Avista Corp. a $103 million termination fee on January 24, 2019. The termination fee was used for reimbursing the Company's transaction costs incurred from 2017 to 2019. The balance of the termination fee remaining after payment of 2019 transaction costs and applicable income taxes was used for general corporate purposes and reduced the Company's need for external financing. The 2019 costs totaled $19.7 million pre-tax and included financial advisers' fees, legal fees, consulting fees and employee time.

Sale of METALfx Sale of METALfx (Notes)	3 Months Ended
Sale of METALfx Sale of METALfx (Notes)	Mar. 31, 2020
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	SALE OF METALfx In April 2019, Bay Area Manufacturing, Inc., a non-regulated subsidiary of Avista Corp., entered into a definitive agreement to sell its interest in METALfx to an independent third party. The transaction was a stock sale for a total cash purchase price of $17.5 million plus cash on-hand, subject to customary closing adjustments. The transaction closed on April 18, 2019, and as of that date the Company has no further involvement with METALfx. The purchase price of $17.5 million, as adjusted, was divided among the security holders of METALfx, including the minority shareholder, pro rata based on ownership (Avista Corp. owned 89.2 percent of the equity of METALfx). As required under the purchase agreement, $1.2 million (7 percent of the purchase price) will be held in escrow for 24 months from the closing of the transaction to satisfy certain indemnification obligations. When all escrow amounts are released, the sale transaction will provide cash proceeds to Avista Corp., net of payments to the minority holder, contractually obligated compensation payments and other transaction expenses, of $16.5 million. The sale has resulted in a net gain after-tax of $3.3 million, with $2.4 million recognized in the three months ended March 31, 2019. The Company expects to receive the full amount of its portion of the escrow accounts; therefore, the full amounts have been included in the gain calculation. The gross gain is included in "Other income," the transaction expenses paid are included in "Non-utility Other operating expenses" and any taxes associated with the sale are included in "Income tax expense" on the Condensed Consolidated Statements of Income. Prior to the completion of the sales transaction, METALfx was not a reportable business segment and was included in other in the business segment footnote at Note 16. This transaction does not meet the criteria for discontinued operations as it does not represent a strategic shift that will have a major effect on the Company's ongoing operations.

Summary Of Significant Accounting Policies (Policy)	3 Months Ended
Summary Of Significant Accounting Policies (Policy)	Mar. 31, 2020
Accounting Policies [Abstract]
Nature Of Business	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, most of whom are employees who operate the Company's Noxon Rapids generating facility. 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 all of the subsidiary companies in the non-utility businesses, with the exception of AJT Mining Properties, Inc., which is a subsidiary of AERC. See Note 16 for business segment information. See Note 18 for discussion of the sale of METALfx, an unregulated subsidiary of the Company.
Basis Of Reporting	Basis of Reporting The condensed 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 condensed consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants.
Derivative Assets And Liabilities	Derivative Assets and Liabilities Derivatives are recorded as either assets or liabilities on the Condensed 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 have been concluded to be 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 that are 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 that is determined to be other-than-temporary. 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 cash payments made or received are recorded as a regulatory asset or liability and are subsequently amortized as a component of interest expense over the life of the associated debt. The settled interest rate swap derivatives are also included as a part of Avista Corp.'s cost of debt calculation for ratemaking purposes. The Company has multiple master netting agreements with a variety of entities that allow 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 any 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 Condensed Consolidated Balance Sheets.
Fair Value Measurements	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, as well as derivatives related to interest rate swaps and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 11 for the Company’s fair value disclosures.
Contingencies	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. See Note 15 for further discussion of the Company's commitments and contingencies.

Balance Sheet Components Balance Sheet Components (Policies)

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Inventory, Policy [Policy Text Block]



	March 31,		December 31,
	2020		2019
Materials and supplies	$	49,007	$	47,402
Fuel stock	4,740		4,875
Stored natural gas	2,934		14,306
Total	$	56,681	$	66,583

Revenue Revenue (Policies)

3 Months Ended

Mar. 31, 2020

Revenue from Contract with Customer [Abstract]

Revenue [Policy Text Block]

Utility Revenues

Revenue from Contracts with Customers

General

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

Non-Derivative Wholesale Contracts

Alternative Revenue Programs (Decoupling)

Derivative Revenue

Other Utility Revenue

Other Considerations for Utility Revenues

Gross Versus Net Presentation

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

Utility-related taxes that were included in revenue from contracts with customers were as follows for the three months ended March 31 (dollars in thousands):



	2020		2019
Utility-related taxes	$	18,700	$	19,089

Non-Utility Revenues

Revenue from Contracts with Customers

Significant Judgments and Unsatisfied Performance Obligations

Revenue Recognition for Alternative Revenue Programs, Policy [Policy Text Block]

Alternative Revenue Programs (Decoupling)

Utility, Revenue and Expense Recognition, Policy [Policy Text Block]

Utility-related taxes that were included in revenue from contracts with customers were as follows for the three months ended March 31 (dollars in thousands):



	2020		2019
Utility-related taxes	$	18,700	$	19,089

Balance Sheet Components Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Schedule of Other Current Assets [Table Text Block]

Other current assets consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$	2,470	$	4,434
Prepayments	22,569		19,652
Income taxes receivable	—		11,047
Other	5,289		5,009
Total	$	30,328	$	40,142

Schedule of Inventory, Current [Table Text Block]



	March 31,		December 31,
	2020		2019
Materials and supplies	$	49,007	$	47,402
Fuel stock	4,740		4,875
Stored natural gas	2,934		14,306
Total	$	56,681	$	66,583

Public Utility Property, Plant, and Equipment [Table Text Block]

Net utility property consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Utility plant in service	$	6,521,033	$	6,462,993
Construction work in progress	189,827		164,941
Total	6,710,860		6,627,934
Less: Accumulated depreciation and amortization	1,868,542		1,830,927
Total net utility property	$	4,842,318	$	4,797,007

Schedule of Other Current Assets [Table Text Block]

Other property and investments-net and other non-current assets consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Operating lease ROU assets	$	65,303	$	69,746
Finance lease ROU assets	50,069		50,980
Non-utility property	26,511		27,159
Equity investments	51,467		51,258
Investment in affiliated trust	11,547		11,547
Notes receivable	14,970		14,060
Deferred compensation assets	8,670		8,948
Other	25,614		23,394
Total	$	254,151	$	257,092

Other Current Liabilities [Table Text Block]

Other current liabilities consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Accrued taxes other than income taxes	$	48,980	$	36,965
Employee paid time off accruals	24,084		22,343
Accrued interest	31,033		16,486
Current portion of pensions and other postretirement benefits	9,811		8,826
Income taxes payable	5,199		298
Derivative liabilities	27,409		10,928
Other current liabilities	27,770		35,133
Total other current liabilities	$	174,286	$	130,979

Other Noncurrent Liabilities [Table Text Block]

Other non-current liabilities and deferred credits consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Operating lease liabilities	$	62,145	$	65,565
Finance lease liabilities	51,016		51,750
Deferred investment tax credits	30,588		30,444
Asset retirement obligations	20,263		20,338
Derivative liabilities	60,278		19,685
Other	13,374		13,407
Total	$	237,664	$	201,189

Schedule Of Regulated Asset And Liability [Table Text Block]

Regulatory assets and liabilities consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31, 2020				December 31, 2019
	Current		Non-Current		Current		Non-Current
Regulatory Assets
Energy commodity derivatives	$	78	$	—	$	6,310	$	264
Decoupling surcharge	10,927		15,504		12,098		14,806
Pension and other postretirement benefit plans	—		206,112		—		208,754
Interest rate swaps	—		246,566		—		168,594
Deferred income taxes	—		96,525		—		95,752
Settlement with Coeur d'Alene Tribe	—		41,005		—		41,332
AFUDC above FERC allowed rate	—		41,333		—		40,749
Demand side management programs	—		8,670		—		12,170
Utility plant to be abandoned	—		31,678		—		31,291
Other regulatory assets	2,052		63,473		3,443		57,090
Total regulatory assets	$	13,057	$	750,866	$	21,851	$	670,802



	March 31, 2020				December 31, 2019
	Current		Non-Current		Current		Non-Current
Regulatory Liabilities
Income tax related liabilities	$	23,975	$	404,046	$	23,803	$	407,549
Deferred natural gas costs	5,449		—		3,189		—
Deferral power costs	23,595		20,716		14,155		23,544
Decoupling rebate	363		5,972		255		2,398
Provision for rate refund (Washington remand case)	8,490		—		3,565		—
Utility plant retirement costs	—		317,203		—		312,403
Interest rate swaps	—		16,136		—		17,088
Other regulatory liabilities	4,464		19,303		6,748		12,454
Total regulatory liabilities	$	66,336	$	783,376	$	51,715	$	775,436

Revenue Revenue (Tables)

3 Months Ended

Mar. 31, 2020

Revenue from Contract with Customer [Abstract]

Revenue from Contract with Customer [Text Block]

REVENUE

Utility Revenues

Revenue from Contracts with Customers

General

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

Non-Derivative Wholesale Contracts

Alternative Revenue Programs (Decoupling)

Derivative Revenue

Other Utility Revenue

Other Considerations for Utility Revenues

Gross Versus Net Presentation

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

Utility-related taxes that were included in revenue from contracts with customers were as follows for the three months ended March 31 (dollars in thousands):



	2020		2019
Utility-related taxes	$	18,700	$	19,089

Non-Utility Revenues

Revenue from Contracts with Customers

Significant Judgments and Unsatisfied Performance Obligations

Disaggregation of Total Operating Revenue

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



	2020			2019
Avista Utilities
Revenue from contracts with customers	$	351,628		$	354,301
Derivative revenues	31,075			24,127
Alternative revenue programs	(4,413		)	(4,658		)
Deferrals and amortizations for rate refunds to customers	(2,606		)	2,135
Other utility revenues	1,521			1,797
Total Avista Utilities	377,205			377,702
AEL&P
Revenue from contracts with customers	12,126			10,736
Deferrals and amortizations for rate refunds to customers	(48		)	(48		)
Other utility revenues	124			193
Total AEL&P	12,202			10,881
Other
Revenue from contracts with customers	514			7,647
Other revenues	309			251
Total other	823			7,898
Total operating revenues	$	390,230		$	396,481

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 three months ended March 31 (dollars in thousands):



	2020						2019
	Avista Utilities		AEL&P		Total Utility		Avista Utilities		AEL&P		Total Utility
ELECTRIC OPERATIONS
Revenue from contracts with customers
Residential	$	107,977	$	5,866	$	113,843	$	115,392	$	5,852	$	121,244
Commercial and governmental	78,849		6,199		85,048		79,245		4,821		84,066
Industrial	24,711		—		24,711		25,248		—		25,248
Public street and highway lighting	1,783		61		1,844		1,903		63		1,966
Total retail revenue	213,320		12,126		225,446		221,788		10,736		232,524
Transmission	3,774		—		3,774		5,152		—		5,152
Other revenue from contracts with customers	5,289		—		5,289		8,194		—		8,194
Total revenue from contracts with customers	$	222,383	$	12,126	$	234,509	$	235,134	$	10,736	$	245,870

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



	2020		2019
	Avista Utilities		Avista Utilities
NATURAL GAS OPERATIONS
Revenue from contracts with customers
Residential	$	84,173	$	77,336
Commercial	39,401		36,595
Industrial and interruptible	2,194		1,627
Total retail revenue	125,768		115,558
Transportation	2,352		2,484
Other revenue from contracts with customers	1,125		1,125
Total revenue from contracts with customers	$	129,245	$	119,167

Disaggregation of Revenue [Table Text Block]

Disaggregation of Total Operating Revenue

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



	2020			2019
Avista Utilities
Revenue from contracts with customers	$	351,628		$	354,301
Derivative revenues	31,075			24,127
Alternative revenue programs	(4,413		)	(4,658		)
Deferrals and amortizations for rate refunds to customers	(2,606		)	2,135
Other utility revenues	1,521			1,797
Total Avista Utilities	377,205			377,702
AEL&P
Revenue from contracts with customers	12,126			10,736
Deferrals and amortizations for rate refunds to customers	(48		)	(48		)
Other utility revenues	124			193
Total AEL&P	12,202			10,881
Other
Revenue from contracts with customers	514			7,647
Other revenues	309			251
Total other	823			7,898
Total operating revenues	$	390,230		$	396,481

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 three months ended March 31 (dollars in thousands):



	2020						2019
	Avista Utilities		AEL&P		Total Utility		Avista Utilities		AEL&P		Total Utility
ELECTRIC OPERATIONS
Revenue from contracts with customers
Residential	$	107,977	$	5,866	$	113,843	$	115,392	$	5,852	$	121,244
Commercial and governmental	78,849		6,199		85,048		79,245		4,821		84,066
Industrial	24,711		—		24,711		25,248		—		25,248
Public street and highway lighting	1,783		61		1,844		1,903		63		1,966
Total retail revenue	213,320		12,126		225,446		221,788		10,736		232,524
Transmission	3,774		—		3,774		5,152		—		5,152
Other revenue from contracts with customers	5,289		—		5,289		8,194		—		8,194
Total revenue from contracts with customers	$	222,383	$	12,126	$	234,509	$	235,134	$	10,736	$	245,870

Schedule Of Utilities Operating Revenue Expense Taxes [Table Text Block]

Utility-related taxes that were included in revenue from contracts with customers were as follows for the three months ended March 31 (dollars in thousands):



	2020		2019
Utility-related taxes	$	18,700	$	19,089

Derivatives And Risk Management (Tables)

3 Months Ended

Mar. 31, 2020

Derivative Instruments and Hedges, Assets [Abstract]

Energy Commodity Derivatives

The following table presents the underlying energy commodity derivative volumes as of March 31, 2020 that are 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
Remainder 2020	3	395	10,232	61,330	366	1,491	871	27,035
2021	—	123	305	32,120	—	246	1,490	21,700
2022	—	—	450	7,820	—	—	—	2,700

As of March 31, 2020, there are no expected deliveries of energy commodity derivatives after 2022.

The following table presents the underlying energy commodity derivative volumes as of December 31, 2019 that are 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
2020	2	442	9,813	78,803	133	1,724	2,984	37,848
2021	—	—	153	25,523	—	246	1,040	13,108
2022	—	—	225	4,725	—	—	—	675

As of December 31, 2019, there are no expected deliveries of energy commodity derivatives after 2022.

(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.

Foreign Currency Exchange Contracts

The following table summarizes the foreign currency exchange derivatives that Avista Corp. has outstanding as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Number of contracts	23		20
Notional amount (in United States dollars)	$	5,219	$	5,932
Notional amount (in Canadian dollars)	7,247		7,828

Interest Rate Swap Agreements

The following table summarizes the unsettled interest rate swap derivatives that Avista Corp. has outstanding as of March 31, 2020 and December 31, 2019 (dollars in thousands):



Balance Sheet Date	Number of Contracts	Notional Amount		Mandatory Cash Settlement Date
March 31, 2020	7	$	70,000	2020
	4	45,000		2021
	11	120,000		2022
	1	10,000		2023
December 31, 2019	7	70,000		2020
	3	35,000		2021
	10	110,000		2022

Derivative Instruments Summary

The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of March 31, 2020 (in thousands):



	Fair Value
Derivative and Balance Sheet Location	Gross Asset		Gross Liability			Collateral Netted			Net Asset (Liability) on Balance Sheet
Foreign currency exchange derivatives
Other current liabilities	$	36	$	(103	)	$	—		$	(67	)
Interest rate swap derivatives
Other current liabilities	—		(32,967		)	12,967			(20,000		)
Other non-current liabilities and deferred credits	—		(79,271		)	14,123			(65,148		)
Energy commodity derivatives
Other current assets	28,964		(26,503		)	(695		)	1,766
Other property and investments-net and other non-current assets	6,072		(3,626		)	—			2,446
Other current liabilities	51		(2,590		)	—			(2,539		)
Other non-current liabilities and deferred credits	—		(24		)	—			(24		)
Total derivative instruments recorded on the balance sheet	$	35,123	$	(145,084	)	$	26,395		$	(83,566	)

The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2019 (in thousands):



	Fair Value
Derivative and Balance Sheet Location	Gross Asset		Gross Liability			Collateral Netted		Net Asset (Liability) on Balance Sheet
Foreign currency exchange derivatives
Other current assets	$	97	$	—		$	—	$	97
Interest rate swap derivatives
Other current assets	589		—			—		589
Other current liabilities	238		(9,379		)	1,316		(7,825		)
Other non-current liabilities and deferred credits	725		(24,677		)	5,454		(18,498		)
Energy commodity derivatives
Other current assets	416		(245		)	—		171
Other property and investments-net and other non-current assets	6,369		(5,446		)	—		923
Other current liabilities	34,760		(41,241		)	3,378		(3,103		)
Other non-current liabilities and deferred credits	28		(1,215		)	—		(1,187		)
Total derivative instruments recorded on the balance sheet	$	43,222	$	(82,203	)	$	10,148	$	(28,833	)

Schedule of Assets Pledged as Collateral and Related Offsets [Table Text Block]

The following table presents Avista Corp.'s collateral outstanding related to its derivative instruments as of March 31, 2020 and December 31, 2019 (in thousands):



	March 31,			December 31,
	2020			2019
Energy commodity derivatives
Cash collateral posted	$	1,775		$	7,812
Letters of credit outstanding	25,000			17,400
Balance sheet offsetting (cash collateral against net derivative positions)	(695		)	3,378

Interest rate swap derivatives
Cash collateral posted	27,090			6,770
Letters of credit outstanding	3,910			—
Balance sheet offsetting (cash collateral against net derivative positions)	27,090			6,770



	March 31,		December 31,
	2020		2019
Energy commodity derivatives
Liabilities with credit-risk-related contingent features	$	1	$	814
Additional collateral to post	1		814

Interest rate swap derivatives
Liabilities with credit-risk-related contingent features	112,238		34,056
Additional collateral to post	81,280		26,912

Pension Plans And Other Postretirement Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2020

Components of Net Periodic Benefit Cost



	Pension Benefits						Other Postretirement Benefits
	2020			2019			2020			2019
Service cost	$	5,546		$	4,874		$	979		$	772
Interest cost	6,971			7,138			1,515			1,372
Expected return on plan assets	(9,125		)	(7,815		)	(630		)	(718		)
Amortization of prior service cost	75			75			(275		)	(275		)
Net loss recognition	1,654			2,415			1,243			1,246
Net periodic benefit cost	$	5,121		$	6,687		$	2,832		$	2,397

Income Taxes Income Taxes (Tables)

3 Months Ended

Mar. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]



	2020					2019
Federal income taxes at statutory rates	$	11,961		21.0	%	$	30,639		21.0	%
Increase (decrease) in tax resulting from:
Tax effect of regulatory treatment of utility plant differences	(2,402		)	(4.2	)	(2,080		)	(1.4	)
State income tax expense	1,227			2.1		1,659			1.1
Acquisition costs	—			—		(1,824		)	(1.2	)
Settlement of equity awards	165			0.3		612			0.4
Other	(2,419		)	(4.2	)	1,011			0.7
Total income tax expense	$	8,532		15.0	%	$	30,017		20.6	%

Committed Lines of Credit (Tables)

3 Months Ended

Mar. 31, 2020

Short-term Debt [Abstract]

Schedule of Line of Credit Facilities [Table Text Block]



	March 31,			December 31,
	2020			2019
Balance outstanding at end of period	$	185,000		$	182,300
Letters of credit outstanding at end of period	$	32,983		$	21,473
Average interest rate at end of period	1.66		%	2.64		%

Long- Term Debt to Affiliated Trust Long-Term Debt to Affiliated Trust (Tables)

3 Months Ended

Mar. 31, 2020

Long-Term Debt to Affiliated Trust [Abstract]

Schedule Of Distribution Rates Paid [Table Text Block]

The distribution rates paid were as follows during the three months ended March 31, 2020 and the year ended December 31, 2019:



	March 31,		December 31,
	2020		2019
Low distribution rate	2.46	%	2.79	%
High distribution rate	2.79	%	3.61	%
Distribution rate at the end of the period	2.46	%	2.79	%

Fair Value (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Inputs, Liabilities, Quantitative Information [Table Text Block]

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 March 31, 2020 (dollars in thousands):



	Fair Value (Net) at
	March 31, 2020			Valuation Technique	Unobservable Input	Range and Weighted Average Price
Natural gas exchange agreement	$	(2,253	)	Internally derived weighted average cost of gas	Forward purchase prices	$1.16 - $1.80/mmBTU $1.47 Weighted Average
					Forward purchase prices	$1.16 - $1.80/mmBTU $1.47 Weighted Average
					Forward sales prices	$1.33 - $3.79/mmBTU $2.96 Weighted Average
					Purchase volumes	155,000 - 310,000 mmBTUs
					Sales volumes	60,000 - 310,000 mmBTUs

Fair Value of Assets And Liabilities Measured on Recurring Basis



	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
March 31, 2020
Assets:
Energy commodity derivatives	$	—	$	35,061	$	—	$	(30,849	)	$	4,212
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		26		(26		)	—
Foreign currency exchange derivatives	—		36		—		(36		)	—
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	2,642		—		—		—			2,642
Equity securities (2)	5,585		—		—		—			5,585
Total	$	8,227	$	35,097	$	26	$	(30,911	)	$	12,439
Liabilities:
Energy commodity derivatives	$	—	$	30,464	$	—	$	(30,154	)	$	310
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		2,279		(26		)	2,253
Foreign currency exchange derivatives	—		103		—		(36		)	67
Interest rate swap derivatives	—		112,238		—		(27,090		)	85,148
Total	$	—	$	142,805	$	2,279	$	(57,306	)	$	87,778



	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2019
Assets:
Energy commodity derivatives	$	—	$	41,546	$	—	$	(40,452	)	$	1,094
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		27		(27		)	—
Foreign currency exchange derivatives	—		97		—		—			97
Interest rate swap derivatives	—		1,552		—		(963		)	589
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	2,232		—		—		—			2,232
Equity securities (2)	6,271		—		—		—			6,271
Total	$	8,503	$	43,195	$	27	$	(41,442	)	$	10,283
Liabilities:
Energy commodity derivatives	$	—	$	45,144	$	—	$	(43,830	)	$	1,314
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		3,003		(27		)	2,976
Interest rate swap derivatives	—		34,056		—		(7,733		)	26,323
Total	$	—	$	79,200	$	3,003	$	(51,590	)	$	30,613


(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 any 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 Condensed Consolidated Balance Sheets.

Reconciliation for All Assets Measured At Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)



	Natural Gas Exchange Agreement			Power Exchange Agreement			Total
Three months ended March 31, 2020:
Balance as of January 1, 2020	$	(2,976	)	$	—		$	(2,976	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	485			—			485
Settlements	238			—			238
Ending balance as of March 31, 2020 (2)	$	(2,253	)	$	—		$	(2,253	)
Three months ended March 31, 2019:
Balance as of January 1, 2019	$	(2,774	)	$	(2,488	)	$	(5,262	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	8,977			(1,018		)	7,959
Settlements	(8,307		)	2,894			(5,413		)
Ending balance as of March 31, 2019 (2)	$	(2,104	)	$	(612	)	$	(2,716	)


(1)	All gains and losses are included in other regulatory assets and liabilities. There were no gains and losses included in either net income or other comprehensive income during any of the periods presented in the table above.

(2)

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

Carrying Value and Estimated Fair Value of Financial Instruments



	March 31, 2020				December 31, 2019
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Long-term debt (Level 2)	$	963,500	$	1,107,956	$	963,500	$	1,124,649
Long-term debt (Level 3)	947,000		949,144		947,000		1,048,440
Snettisham finance lease obligation (Level 3)	53,850		56,900		54,550		58,000
Long-term debt to affiliated trusts (Level 3)	51,547		33,506		51,547		41,238

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss (Tables)

3 Months Ended

Mar. 31, 2020

Accumulated Other Comprehensive Loss [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

Accumulated other comprehensive loss, net of tax, consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):



	March 31,		December 31,
	2020		2019
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $2,673 and $2,727, respectively	$	10,054	$	10,259

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]

The following table details the reclassifications out of accumulated other comprehensive loss to net income by component for the three months ended March 31 (dollars in thousands).



	Amounts Reclassified from Accumulated Other Comprehensive Loss
Details about Accumulated Other Comprehensive Loss Components	2020			2019			Affected Line Item in Statement of Income
Amortization of defined benefit pension items
Amortization of net prior service cost	$	(200	)	$	(200	)	(a)
Amortization of net loss	3,100			3,661			(a)
Adjustment due to effects of regulation	(2,641		)	(3,258		)	(a)
	259			203			Total before tax
	(54		)	(43		)	Tax expense
	$	205		$	160		Net of tax

(a)

These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 6 for additional details).

Earnings Per Common Share Attributable To Avista Corporation (Tables)

3 Months Ended

Mar. 31, 2020

Earnings Per Share [Abstract]

Computations Of Earnings Per Share



	2020		2019
Numerator:
Net income attributable to Avista Corp. shareholders	$	48,424	$	115,794
Denominator:
Weighted-average number of common shares outstanding-basic	67,239		65,733
Effect of dilutive securities:
Performance and restricted stock awards	142		208
Weighted-average number of common shares outstanding-diluted	67,381		65,941
Earnings per common share attributable to Avista Corp. shareholders:
Basic	$	0.72	$	1.76
Diluted	$	0.72	$	1.76

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

Information By Business Segments (Tables)

3 Months Ended

Mar. 31, 2020

Segment Reporting [Abstract]

Information by 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 three months ended March 31, 2020:
Operating revenues	$	377,205	$	12,202		$	389,407	$	823		$	—		$	390,230
Resource costs	129,557		(10		)	129,547		—			—			129,547
Other operating expenses	91,279		3,217			94,496		1,360			—			95,856
Depreciation and amortization	48,974		2,447			51,421		235			—			51,656
Income (loss) from operations	76,534		6,246			82,780		(587		)	—			82,193
Interest expense (3)	24,983		1,589			26,572		131			(86		)	26,617
Income taxes	7,404		1,301			8,705		(173		)	—			8,532
Net income (loss) attributable to Avista Corp. shareholders	45,979		3,395			49,374		(950		)	—			48,424
Capital expenditures (4)	94,056		1,470			95,526		109			—			95,635
For the three months ended March 31, 2019:
Operating revenues	$	377,702	$	10,881		$	388,583	$	7,898		$	—		$	396,481
Resource costs	138,712		(1,365		)	137,347		—			—			137,347
Other operating expenses (2)	100,583		3,059			103,642		7,355			—			110,997
Depreciation and amortization	46,507		2,407			48,914		209			—			49,123
Income from operations	60,224		6,513			66,737		334			—			67,071
Interest expense (3)	24,264		1,596			25,860		588			(440		)	26,008
Income taxes	28,544		1,363			29,907		110			—			30,017
Net income attributable to Avista Corp. shareholders	111,901		3,552			115,453		341			—			115,794
Capital expenditures (4)	92,309		1,306			93,615		162			—			93,777
Total Assets:
As of March 31, 2020:	$	5,808,619	$	272,178		$	6,080,797	$	112,213		$	(19,011	)	$	6,173,999
As of December 31, 2019:	$	5,713,268	$	271,393		$	5,984,661	$	113,390		$	(15,595	)	$	6,082,456


(1)	Intersegment eliminations reported as interest expense represent intercompany interest.


(2)	Other operating expenses for Avista Utilities for the three months ended March 31, 2019 include merger transaction costs which are separately disclosed on the Condensed Consolidated Statements of Income.


(3)	Including interest expense to affiliated trusts.

(4)

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

Balance Sheet Components Materials and Supplies, Fuel Stock and Stored Natural Gas (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Inventory, Raw Materials and Supplies, Gross	$ 49,007	$ 47,402
Other Inventory, Gross	4,740	4,875
Energy Related Inventory, Gas Stored Underground	2,934	14,306
Inventory, Net	$ 56,681	$ 66,583

Balance Sheet Components Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$ 2,470	$ 4,434
Prepayments	22,569	19,652
Income taxes receivable	0	11,047
Other	5,289	5,009
Other Assets, Current	$ 30,328	$ 40,142

Balance Sheet Components Net Utility Property (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Utility plant in service	$ 6,521,033	$ 6,462,993
Construction work in progress	189,827	164,941
Total	6,710,860	6,627,934
Less: Accumulated depreciation and amortization	1,868,542	1,830,927
Total net utility property	$ 4,842,318	$ 4,797,007

Balance Sheet Components Other Property and Investments-Net and Non-current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Operating Lease, Right-of-Use Asset	$ 65,303	$ 69,746
Finance Lease, Right-of-Use Asset	50,069	50,980
Non-utility property	26,511	27,159
Equity investments	51,467	51,258
Investment in affiliated trust	11,547	11,547
Notes receivable	14,970	14,060
Deferred compensation assets	8,670	8,948
Other	25,614	23,394
Investments and Other Noncurrent Assets	$ 254,151	$ 257,092

Balance Sheet Components Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued taxes other than income taxes	$ 48,980	$ 36,965
Employee paid time off accruals	24,084	22,343
Accrued interest	31,033	16,486
Current portion of pensions and other postretirement benefits	9,811	8,826
Taxes Payable, Current	5,199	298
Derivative liabilities	27,409	10,928
Other current liabilities	27,770	35,133
Other current liabilities	$ 174,286	$ 130,979

Balance Sheet Components Other Non-Current Liabilities and Deferred Credits (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Operating Lease, Liability, Noncurrent	$ 62,145	$ 65,565
Finance Lease, Liability, Noncurrent	51,016	51,750
Deferred investment tax credits	30,588	30,444
Asset Retirement Obligation	20,263	20,338
Derivative Liability, Noncurrent	60,278	19,685
Other	13,374	13,407
Other Liabilities, Noncurrent	$ 237,664	$ 201,189

Balance Sheet Components Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Regulated Asset Liability [Line Items]
Regulatory assets	$ 13,057	$ 21,851
Regulatory Assets, Noncurrent	750,866	670,802
Regulatory liabilities	66,336	51,715
Non-current regulatory liabilities	783,376	775,436
Provision for Rate Refunds [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	8,490	3,565
Non-current regulatory liabilities	0	0
Income Tax Related
Regulated Asset Liability [Line Items]
Regulatory liabilities	23,975	23,803
Non-current regulatory liabilities	404,046	407,549
Natural Gas Deferrals [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	5,449	3,189
Non-current regulatory liabilities	0	0
Power Deferrals Regulatory Liability [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	23,595	14,155
Non-current regulatory liabilities	20,716	23,544
Decoupling surcharge
Regulated Asset Liability [Line Items]
Regulatory liabilities	363	255
Non-current regulatory liabilities	5,972	2,398
Removal Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	0	0
Non-current regulatory liabilities	317,203	312,403
Interest rate swaps
Regulated Asset Liability [Line Items]
Regulatory liabilities	0	0
Non-current regulatory liabilities	16,136	17,088
Other Regulatory Assets (Liabilities) [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	4,464	6,748
Non-current regulatory liabilities	19,303	12,454
Energy commodity derivatives
Regulated Asset Liability [Line Items]
Regulatory assets	78	6,310
Regulatory Assets, Noncurrent	0	264
Decoupling surcharge
Regulated Asset Liability [Line Items]
Regulatory assets	10,927	12,098
Regulatory Assets, Noncurrent	15,504	14,806
Pension and other postretirement benefit plans
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	206,112	208,754
Interest rate swaps
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	246,566	168,594
Income Tax Related
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	96,525	95,752
Settlement with Coeur d'Alene Tribe
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	41,005	41,332
AFUDC above FERC allowed rate
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	41,333	40,749
Demand side management programs
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	8,670	12,170
Utility plant to be abandoned
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	31,678	31,291
Other Regulatory Assets (Liabilities) [Member]
Regulated Asset Liability [Line Items]
Regulatory assets	2,052	3,443
Regulatory Assets, Noncurrent	$ 63,473	$ 57,090

Revenue Revenue Utility Related Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Public Utility Operating Expenses Excise Taxes Collected	$ 18,700	$ 19,089

Revenue Revenue Unsatisfied Performance Obligations (Details) $ in Millions	Mar. 31, 2020 USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 4.7

Revenue Revenue Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 390,230	$ 396,481
Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	113,843	121,244
Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	85,048	84,066
Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	24,711	25,248
Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,844	1,966
Total Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	225,446	232,524
Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,774	5,152
Other Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,289	8,194
Total Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	234,509	245,870
Avista Utilities [Member]
Disaggregation of Revenue [Line Items]
Revenues	377,205	377,702
Avista Utilities [Member] \| Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	107,977	115,392
Avista Utilities [Member] \| Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	78,849	79,245
Avista Utilities [Member] \| Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	24,711	25,248
Avista Utilities [Member] \| Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,783	1,903
Avista Utilities [Member] \| Total Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	213,320	221,788
Avista Utilities [Member] \| Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,774	5,152
Avista Utilities [Member] \| Other Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,289	8,194
Avista Utilities [Member] \| Total Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	222,383	235,134
Avista Utilities [Member] \| Residential Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	84,173	77,336
Avista Utilities [Member] \| Commercial Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	39,401	36,595
Avista Utilities [Member] \| Industrial and Interruptible Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,194	1,627
Avista Utilities [Member] \| Total Retail Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	125,768	115,558
Avista Utilities [Member] \| Transportation Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,352	2,484
Avista Utilities [Member] \| Other Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,125	1,125
Avista Utilities [Member] \| Total Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	129,245	119,167
Avista Utilities [Member] \| Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	351,628	354,301
Avista Utilities [Member] \| Derivative revenues
Disaggregation of Revenue [Line Items]
Revenues	31,075	24,127
Avista Utilities [Member] \| Alternative Revenue Programs [Member]
Disaggregation of Revenue [Line Items]
Revenues	(4,413)	(4,658)
Avista Utilities [Member] \| Deferrals and amortizations for rate refunds to customers
Disaggregation of Revenue [Line Items]
Revenues	(2,606)	2,135
Avista Utilities [Member] \| Other utility revenues
Disaggregation of Revenue [Line Items]
Revenues	1,521	1,797
Alaska Electric Light & Power [Member]
Disaggregation of Revenue [Line Items]
Revenues	12,202	10,881
Alaska Electric Light & Power [Member] \| Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,866	5,852
Alaska Electric Light & Power [Member] \| Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6,199	4,821
Alaska Electric Light & Power [Member] \| Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Alaska Electric Light & Power [Member] \| Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	61	63
Alaska Electric Light & Power [Member] \| Total Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12,126	10,736
Alaska Electric Light & Power [Member] \| Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Alaska Electric Light & Power [Member] \| Other Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0
Alaska Electric Light & Power [Member] \| Total Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12,126	10,736
Alaska Electric Light & Power [Member] \| Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	12,126	10,736
Alaska Electric Light & Power [Member] \| Deferrals and amortizations for rate refunds to customers
Disaggregation of Revenue [Line Items]
Revenues	(48)	(48)
Alaska Electric Light & Power [Member] \| Other utility revenues
Disaggregation of Revenue [Line Items]
Revenues	124	193
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	823	7,898
Corporate and Other [Member] \| Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	514	7,647
Corporate and Other [Member] \| Other revenues
Disaggregation of Revenue [Line Items]
Revenues	$ 309	$ 251

Derivatives And Risk Management (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net	$ 26,395	$ 10,148
Commodity Contracts [Member]
Derivative [Line Items]
Cash deposited as collateral	1,775	7,812
Letters of credit outstanding	25,000	17,400
Derivative, Fair Value, Amount Offset Against Collateral, Net	(695)	3,378
Liability position at aggregate fair value	1	814
Additional Collateral, Aggregate Fair Value	1	814
Interest Rate Swap [Member]
Derivative [Line Items]
Cash deposited as collateral	27,090	6,770
Letters of credit outstanding	3,910	0
Derivative, Fair Value, Amount Offset Against Collateral, Net	27,090	6,770
Liability position at aggregate fair value	112,238	34,056
Additional Collateral, Aggregate Fair Value	$ 81,280	$ 26,912

Derivatives And Risk Management (Energy Commodity Derivatives) (Details) frequency in Thousands, Volt in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020 Volt frequency	Dec. 31, 2019 Volt frequency
Sales [Member] \| Physical [Member] \| Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020	366	133
2021	0	0
2022	0	0
2023	0	0
2024	0	0
Thereafter	0	0
Sales [Member] \| Physical [Member] \| Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020 \| Volt	871	2,984
2021 \| Volt	1,490	1,040
2022 \| Volt	0	0
2023	0	0
2024	0	0
Thereafter \| Volt	0	0
Sales [Member] \| Financial [Member] \| Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020	1,491	1,724
2021	246	246
2022	0	0
2023	0	0
2024	0	0
Thereafter	0	0
Sales [Member] \| Financial [Member] \| Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020 \| Volt	27,035	37,848
2021 \| Volt	21,700	13,108
2022 \| Volt	2,700	675
2023 \| Volt	0	0
2024	0	0
Thereafter \| Volt	0	0
Purchase [Member] \| Physical [Member] \| Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020	3	2
2021	0	0
2022	0	0
2023	0	0
2024	0	0
Thereafter	0	0
Purchase [Member] \| Physical [Member] \| Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020 \| Volt	10,232	9,813
2021 \| Volt	305	153
2022 \| Volt	450	225
2023 \| Volt	0	0
2024 \| Volt	0	0
Thereafter \| Volt	0	0
Purchase [Member] \| Financial [Member] \| Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020	395	442
2021	123	0
2022	0	0
2023	0	0
2024	0	0
Thereafter	0	0
Purchase [Member] \| Financial [Member] \| Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2020 \| Volt	61,330	78,803
2021 \| Volt	32,120	25,523
2022 \| Volt	7,820	4,725
2023 \| Volt	0	0
2024 \| Volt	0	0
Thereafter \| Volt	0	0

Derivatives And Risk Management Derivatives and Risk Management (Foreign Currency Exchange Contracts) (Details) $ in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020 CAD ($) derivative_contracts	Mar. 31, 2020 USD ($) derivative_contracts	Dec. 31, 2019 CAD ($) derivative_contracts	Dec. 31, 2019 USD ($) derivative_contracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Number Of Days Canadian Currency Prices Are Settled With U.S. Dollars	60 days
Number of Foreign Currency Derivatives Held \| derivative_contracts	23	23	20	20
United States of America, Dollars \| Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Derivative, Notional Amount		$ 5,219		$ 5,932
Canada, Dollars \| Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Derivative, Notional Amount	$ 7,247		$ 7,828

Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) Caontracts	Dec. 31, 2019 USD ($) Caontracts
Derivatives, Fair Value [Line Items]
Document Period End Date	Mar. 31, 2020
2020 \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held \| Caontracts	7	7
Derivative, Notional Amount \| $	$ 70,000	$ 70,000
Mandatory Cash Settlement Date	2020	2020
2021 \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held \| Caontracts	4	3
Derivative, Notional Amount \| $	$ 45,000	$ 35,000
Mandatory Cash Settlement Date	2021	2021
2022 \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held \| Caontracts	11	10
Derivative, Notional Amount \| $	$ 120,000	$ 110,000
Mandatory Cash Settlement Date	2022	2022
2023 \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held \| Caontracts	1
Derivative, Notional Amount \| $	$ 10,000
Mandatory Cash Settlement Date	2023

Derivatives And Risk Management (Derivative Instruments Summary) (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Gross Asset	$ 35,123,000	$ 43,222,000
Gross Liability	(145,084,000)	(82,203,000)
Collateral Netted	26,395,000	10,148,000
Net Asset (Liability) on Balance Sheet	(83,566,000)	(28,833,000)
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	27,090,000	6,770,000
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	(695,000)	3,378,000
Other Current Liabilities [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	36,000
Gross Liability	(103,000)
Collateral Netted	0
Net Asset (Liability) on Balance Sheet	(67,000)
Other Current Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	238,000
Gross Liability	(32,967,000)	(9,379,000)
Collateral Netted	12,967,000	1,316,000
Net Asset (Liability) on Balance Sheet	(20,000,000)	(7,825,000)
Other Current Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	51,000	34,760,000
Gross Liability	(2,590,000)	(41,241,000)
Collateral Netted	0	3,378,000
Net Asset (Liability) on Balance Sheet	(2,539,000)	(3,103,000)
Other Current Assets [Member] \| Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		97,000
Gross Liability		0
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		97,000
Other Current Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		589,000
Gross Liability		0
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		589,000
Other Current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	28,964,000	416,000
Gross Liability	(26,503,000)	(245,000)
Collateral Netted	(695,000)	0
Net Asset (Liability) on Balance Sheet	1,766,000	171,000
Other Property And Investments Net And Other Non-current Assets [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	6,072,000	6,369,000
Gross Liability	(3,626,000)	(5,446,000)
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	2,446,000	923,000
Other Noncurrent Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	725,000
Gross Liability	(79,271,000)	(24,677,000)
Collateral Netted	14,123,000	5,454,000
Net Asset (Liability) on Balance Sheet	(65,148,000)	(18,498,000)
Other Noncurrent Liabilities [Member] \| Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0	28,000
Gross Liability	(24,000)	(1,215,000)
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	$ (24,000)	$ (1,187,000)

Derivatives And Risk Management Derivatives and Risk Management (Collateral) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net	$ 26,395	$ 10,148
Commodity Contracts [Member]
Derivative [Line Items]
Liability position at aggregate fair value	1	814
Additional Collateral, Aggregate Fair Value	1	814
Collateral Already Posted, Aggregate Fair Value	1,775	7,812
Letters of credit outstanding	25,000	17,400
Derivative, Fair Value, Amount Offset Against Collateral, Net	(695)	3,378
Foreign Exchange Contract [Member]
Derivative [Line Items]
Collateral Already Posted, Aggregate Fair Value	0	0
Letters of credit outstanding	0	0
Interest Rate Swap [Member]
Derivative [Line Items]
Liability position at aggregate fair value	112,238	34,056
Additional Collateral, Aggregate Fair Value	81,280	26,912
Collateral Already Posted, Aggregate Fair Value	27,090	6,770
Letters of credit outstanding	3,910	0
Derivative, Fair Value, Amount Offset Against Collateral, Net	$ 27,090	$ 6,770

Pension Plans And Other Postretirement Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits	$ 7,300	$ 7,300
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	$ 22,000

Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Percentage of Service Related Net Periodic Benefit Costs Capitalized to Utility Property	40.00%
Percentage of Service Related Net Periodic Benefit Costs Recorded to Operating Expenses	60.00%
Percentage of Non-service Related Net Periodic Benefit Costs Capitalized to Regulatory Assets	40.00%
Percentage of Non-service Related Net Periodic Benefit Costs Recorded to Other Expense	60.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5,546	$ 4,874
Interest cost	6,971	7,138
Expected return on plan assets	(9,125)	(7,815)
Amortization of prior service cost	75	75
Net loss recognition	1,654	2,415
Net periodic benefit cost	5,121	6,687
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	979	772
Interest cost	1,515	1,372
Expected return on plan assets	(630)	(718)
Amortization of prior service cost	(275)	(275)
Net loss recognition	1,243	1,246
Net periodic benefit cost	$ 2,832	$ 2,397

Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 11,961	$ 30,639
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Tax Effect Of Regulatory Treatment Of Utility Plant Differences	$ (2,402)	$ (2,080)
Tax Effect Of Regulatory Treatment Of Utility Plant Differences, Percent	(4.20%)	(1.40%)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	$ 1,227	$ 1,659
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	2.10%	1.10%
Income Tax Reconciliation, Nondeductible Expense, Acquisition Costs, Amount	$ 0	$ (1,824)
Income Tax Reconciliation, Nondeductible Expense, Acquisition Costs, Percent	0.00%	(1.20%)
Income Tax Reconciliation Settlement of Share Based Compensation Amount	$ 165	$ 612
Income Tax Reconciliation Settlement of Share Based Compensation Percent	0.30%	0.40%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ (2,419)	$ 1,011
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	(4.20%)	0.70%
Income tax expense	$ 8,532	$ 30,017
Effective Income Tax Rate Reconciliation, Percent	15.00%	20.60%

Committed Lines of Credit (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Jul. 01, 2014	Apr. 30, 2014
Short-term Debt [Line Items]
Document Period End Date	Mar. 31, 2020
Avista Utilities [Member]
Short-term Debt [Line Items]
Line of Credit, Current	$ 185,000	$ 182,300
Line of Credit Facility, Maximum Borrowing Capacity				$ 400,000
Letters of credit outstanding at end of period	$ 32,983	$ 21,473
Average interest rate at end of period	1.66%	2.64%
Alaska Electric Light & Power [Member]
Short-term Debt [Line Items]
Line of Credit, Current	$ 0	$ 3,500
Line of Credit Facility, Maximum Borrowing Capacity			$ 25,000
Letters of credit outstanding at end of period	$ 0	$ 0

Credit Agreement Credit Agreement (Details) - Subsequent Event [Member] - Avista Utilities [Member] $ in Millions	Apr. 06, 2020 USD ($)
Short-term Debt [Line Items]
Maximum Borrowing Capacity Credit Agreement	$ 100
Credit Agreement Amount Borrowed	$ 100

Long- Term Debt to Affiliated Trust Long-Term Debt to Affiliated Trust (Schedule of Distribution Rates Paid) (Details) - Trust Preferred Securities Subject to Mandatory Redemption [Member]	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Interest Rate at End of Period	2.46%	2.79%
Minimum [Member]
Debt Instrument [Line Items]
Interest Rate at End of Period	2.46%	2.79%
Maximum [Member]
Debt Instrument [Line Items]
Interest Rate at End of Period	2.79%	3.61%

Long- Term Debt to Affiliated Trust Long-Term Debt to Affiliated Trust (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2000	Dec. 31, 1997
Debt Instrument [Line Items]
Proceeds From The Issuance of Common Trust Securities			$ 1.5
Payments for Repurchase of Trust Preferred Securities		$ 10.0
Equity Method Investment, Ownership Percentage	100.00%
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	$ 51.5		51.5
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	LIBOR
Debt Instrument, Basis Spread on Variable Rate	0.875%
Proceeds from (Repurchase of) Trust Preferred Securities			$ 50.0

Fair Value (Carrying Value And Estimated Fair Value Of Financial Instruments) (Details) $ in Thousands	Mar. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($)
Level 2 [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 1,107,956	$ 1,124,649
Level 2 [Member] \| Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	963,500	963,500
Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	949,144	1,048,440
Level 3 [Member] \| Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	947,000	947,000
Alaska Electric Light & Power [Member] \| Finance Lease [Member] \| Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease, Liability	56,900	58,000
Alaska Electric Light & Power [Member] \| Finance Lease [Member] \| Level 3 [Member] \| Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease, Liability	53,850	54,550
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	33,506	41,238
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
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 \| $ / shares	100.0
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 \| $ / shares	65.00
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 \| $ / shares	133.98

Fair Value (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	$ 35,123	$ 43,222
Liability	145,084	82,203
Cash and cash equivalents	18,919	9,896	$ 14,861	$ 14,656
Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	400	400
Fair Value, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	(30,911)	(41,442)
Assets, Fair Value Disclosure	12,439	10,283
Counterparty and collateral netting, liabilities	(57,306)	(51,590)
Financial Liabilities Fair Value Disclosure	87,778	30,613
Fair Value, Recurring [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	(26)	(27)
Derivative Asset	0	0
Counterparty and collateral netting, liabilities	(26)	(27)
Derivative Liability	2,253	2,976
Fair Value, Recurring [Member] \| Interest Rate Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets		(963)
Derivative Asset		589
Counterparty and collateral netting, liabilities	(27,090)	(7,733)
Derivative Liability	85,148	26,323
Fair Value, Recurring [Member] \| Energy commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	(30,849)	(40,452)
Derivative Asset	4,212	1,094
Counterparty and collateral netting, liabilities	(30,154)	(43,830)
Derivative Liability	310	1,314
Fair Value, Recurring [Member] \| Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	(36)
Derivative Asset	0	97
Counterparty and collateral netting, liabilities	(36)
Derivative Liability	67
Fair Value, Recurring [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	8,227	8,503
Financial Liabilities Fair Value Disclosure	0	0
Fair Value, Recurring [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	35,097	43,195
Financial Liabilities Fair Value Disclosure	142,805	79,200
Fair Value, Recurring [Member] \| Level 2 [Member] \| Interest Rate Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		1,552
Liability	112,238	34,056
Fair Value, Recurring [Member] \| Level 2 [Member] \| Energy commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	35,061	41,546
Liability	30,464	45,144
Fair Value, Recurring [Member] \| Level 2 [Member] \| Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	36	97
Liability	103
Fair Value, Recurring [Member] \| Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	26	27
Financial Liabilities Fair Value Disclosure	2,279	3,003
Fair Value, Recurring [Member] \| Level 3 [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	26	27
Liability	2,279	3,003
Fixed Income Funds [Member] \| Fair Value, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	2,642	2,232
Fixed Income Funds [Member] \| Fair Value, Recurring [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	2,642	2,232
Equity Funds [Member] \| Fair Value, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	5,585	6,271
Equity Funds [Member] \| Fair Value, Recurring [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	$ 5,585	$ 6,271

Fair Value (Quantitative Information) (Details) - Natural Gas Exchange Agreements [Member] $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) MMBTU $ / MmBtu	Dec. 31, 2019 USD ($)
Fair Value, Recurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative Liability \| $	$ (2,253)	$ (2,976)
Sales [Member] \| Minimum [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price	1.33
Transaction/Delivery Volumes \| MMBTU	60,000
Sales [Member] \| Maximum [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price	3.79
Transaction/Delivery Volumes \| MMBTU	310,000
Sales [Member] \| Weighted Average [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price	2.96
Purchase [Member] \| Minimum [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price	1.16
Transaction/Delivery Volumes \| MMBTU	155,000
Purchase [Member] \| Maximum [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price	1.80
Transaction/Delivery Volumes \| MMBTU	310,000
Purchase [Member] \| Weighted Average [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price	1.47

Fair Value (Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) - Level 3 [Member] - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (2,976,000)	$ (5,262,000)
Gain (Loss) Included in Earnings	0	0
Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0
Included in regulatory assets/liabilities	485,000	7,959,000
Purchases	0	0
Issuances	0	0
Settlements	238,000	(5,413,000)
Transfers, Net	0	0
Ending Balance	(2,253,000)	(2,716,000)
Natural Gas Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(2,976,000)	(2,774,000)
Gain (Loss) Included in Earnings	0	0
Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0
Included in regulatory assets/liabilities	485,000	8,977,000
Purchases	0	0
Issuances	0	0
Settlements	238,000	(8,307,000)
Transfers, Net	0	0
Ending Balance	(2,253,000)	(2,104,000)
Power Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0	(2,488,000)
Gain (Loss) Included in Earnings	0	0
Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0
Included in regulatory assets/liabilities	0	(1,018,000)
Purchases	0	0
Issuances	0	0
Settlements	0	2,894,000
Transfers, Net	0	0
Ending Balance	$ 0	$ (612,000)

Common Stock Common Stock (Details) - Common Stock [Member] - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Class of Stock [Line Items]
Shares issued under sales agency agreements	115,237	61,576
Sales Agency Agreement [Member]
Class of Stock [Line Items]
Shares issued under sales agency agreements	0

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss Reclassifications from AOCL (Details) - Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net prior service cost	$ (200)	$ (200)
Amortization of net loss	3,100	3,661
Adjustment due to effects of regulation	(2,641)	(3,258)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax	259	203
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	(54)	(43)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	$ 205	$ 160

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Loss [Abstract]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans Net Unamortized (Gain) Loss, Tax	$ 2,673	$ 2,727
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	$ 10,054	$ 10,259

Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net income from continuing operations attributable to Avista Corp. shareholders	$ 48,424	$ 115,794
Denominator:
Weighted-average number of common shares outstanding-basic	67,239	65,733
Performance and restricted stock awards	142	208
Weighted-average number of common shares outstanding-diluted	67,381	65,941
Earnings Per Share, Basic [Abstract]
Basic	$ 0.72	$ 1.76
Earnings Per Share, Diluted [Abstract]
Diluted	$ 0.72	$ 1.76

Commitments And Contingencies (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Regulatory liabilities	$ 66,336	$ 51,715
Provision for Rate Refunds [Member]
Loss Contingencies [Line Items]
Regulatory liabilities	8,490	3,565
Provision for Rate Refunds [Member] \| Natural Gas [Member]
Loss Contingencies [Line Items]
Regulatory liabilities	3,600
Provision for Rate Refunds [Member] \| Electricity [Member]
Loss Contingencies [Line Items]
Regulatory liabilities	$ 4,900	$ 3,600

Information By Business Segments (Details) $ in Thousands	3 Months Ended
Information By Business Segments (Details) $ in Thousands	Mar. 31, 2020 USD ($) Reportable_Segments	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments \| Reportable_Segments	2
Operating revenues	$ 390,230	$ 396,481
Resource costs	129,547	137,347
Other operating expenses	95,856	110,997
Depreciation and amortization	51,656	49,123
Income from operations	82,193	67,071
Interest expense	26,617	26,008
Income taxes	8,532	30,017
Net income from continuing operations attributable to Avista Corp. shareholders	48,424	115,794
Capital Expenditures	95,635	93,777
Total assets	6,173,999		$ 6,082,456
Avista Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	377,205	377,702
Alaska Electric Light & Power [Member]
Segment Reporting Information [Line Items]
Operating revenues	12,202	10,881
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	823	7,898
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Resource costs	0	0
Other operating expenses	0	0
Depreciation and amortization	0	0
Income from operations	0	0
Interest expense	(86)	(440)
Income taxes	0	0
Net income from continuing operations attributable to Avista Corp. shareholders	0	0
Capital Expenditures	0	0
Total assets	(19,011)		(15,595)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	389,407	388,583
Resource costs	129,547	137,347
Other operating expenses	94,496	103,642
Depreciation and amortization	51,421	48,914
Income from operations	82,780	66,737
Interest expense	26,572	25,860
Income taxes	8,705	29,907
Net income from continuing operations attributable to Avista Corp. shareholders	49,374	115,453
Capital Expenditures	95,526	93,615
Total assets	6,080,797		5,984,661
Operating Segments [Member] \| Avista Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	377,205	377,702
Resource costs	129,557	138,712
Other operating expenses	91,279	100,583
Depreciation and amortization	48,974	46,507
Income from operations	76,534	60,224
Interest expense	24,983	24,264
Income taxes	7,404	28,544
Net income from continuing operations attributable to Avista Corp. shareholders	45,979	111,901
Capital Expenditures	94,056	92,309
Total assets	5,808,619		5,713,268
Operating Segments [Member] \| Alaska Electric Light & Power [Member]
Segment Reporting Information [Line Items]
Operating revenues	12,202	10,881
Resource costs	(10)	(1,365)
Other operating expenses	3,217	3,059
Depreciation and amortization	2,447	2,407
Income from operations	6,246	6,513
Interest expense	1,589	1,596
Income taxes	1,301	1,363
Net income from continuing operations attributable to Avista Corp. shareholders	3,395	3,552
Capital Expenditures	1,470	1,306
Total assets	272,178		271,393
Operating Segments [Member] \| Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	823	7,898
Resource costs	0	0
Other operating expenses	1,360	7,355
Depreciation and amortization	235	209
Income from operations	(587)	334
Interest expense	131	588
Income taxes	(173)	110
Net income from continuing operations attributable to Avista Corp. shareholders	(950)	341
Capital Expenditures	109	$ 162
Total assets	$ 112,213		$ 113,390

Termination of Proposed Acquisition by Hydro One Termination of Proposed Acquisition by Hydro One (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Jan. 24, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Business Acquisition [Line Items]
Merger termination fee		$ 0	$ 103,000
Merger transaction costs		$ 0	$ 19,664	$ 19,700
Hydro One [Member]
Business Acquisition [Line Items]
Merger termination fee	$ 103,000

Sale of METALfx Sale of METALfx (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2019	Apr. 18, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent			89.20%
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group Including Discontinued Operation Gross Consideration			$ 17.5
Disposal Group Including Discontinued Operation Consideration Held in Escrow			$ 1.2
Disposal Group Including Discontinued Operation Percentage of Gross Consideration Held in Escrow			7.00%
Disposal Group, Including Discontinued Operation, Consideration			$ 16.5
Disposal Group Not Discontinued Operation Gain (Loss) On Disposal Net of Tax	$ 2.4	$ 3.3