Avista (AVA) 10-K 23 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Jan. 31, 2022	Jun. 30, 2021
Cover [Abstract]
Entity Filer Category	Large Accelerated Filer
Title of 12(b) Security	Common Stock
Entity Incorporation, State or Country Code	WA
Entity Registrant Name	AVISTA CORPORATION
Document Transition Report	false
Document Annual Report	true
Document Type	10-K
Document Period End Date	Dec. 31, 2021
Entity File Number	001-03701
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
City Area Code	509
Local Phone Number	489-0500
Trading Symbol	AVA
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 2,972,676,681
Entity Common Stock, Shares Outstanding		71,572,570
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0000104918
Current Fiscal Year End Date	--12-31
ICFR Auditor Attestation Flag	true
Documents Incorporated by Reference	Documents Incorporated By Reference Document Part of Form 10-K into Which Document is Incorporated Proxy Statement to be filed in connection with the annual meeting of shareholders to be held on May 12, 2022. Prior to such filing, the Proxy Statement was filed in connection with the annual meeting of shareholders held on May 11, 2021. Part III, Items 10, 11, 12, 13 and 14
Auditor Name	Deloitte & Touche LLP
Auditor Location	Portland, Oregon
Auditor Firm ID	34

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Utility revenues:
Utility revenues, exclusive of alternative revenue programs	$ 1,445,000	$ 1,324,091	$ 1,323,524
Alternative revenue programs	(6,635)	(3,814)	9,614
Total utility revenues	1,438,365	1,320,277	1,333,138
Non-utility revenues	571	1,614	12,484
Total operating revenues	1,438,936	1,321,891	1,345,622
Utility operating expenses:
Resource costs	497,123	398,509	439,817
Other operating expenses	366,125	354,614	345,212
Merger transaction costs			19,675
Depreciation and amortization	231,915	223,507	205,365
Taxes other than income taxes	109,353	106,501	105,652
Non-utility operating expenses:
Other operating expenses	5,927	5,344	18,883
Depreciation and amortization	261	716	629
Total operating expenses	1,210,704	1,089,191	1,135,233
Income from operations	228,232	232,700	210,389
Interest expense	105,731	104,348	103,012
Interest expense to affiliated trusts	421	713	1,342
Capitalized interest	(3,987)	(4,083)	(4,174)
Merger termination fee			(103,000)
Other income-net	(33,298)	(4,817)	(14,928)
Income before income taxes	159,365	136,539	228,137
Income tax expense	12,031	7,051	31,374
Net income	147,334	129,488	196,763
Net loss attributable to noncontrolling interests			(216)
Net income attributable to Avista Corp. shareholders	$ 147,334	$ 129,488	$ 196,979
Weighted-average common shares outstanding (thousands), basic	69,951	67,962	66,205
Weighted-average common shares outstanding (thousands), diluted	70,085	68,102	66,329
Earnings per common share attributable to Avista Corp. shareholders:
Basic	$ 2.11	$ 1.91	$ 2.98
Diluted	$ 2.10	$ 1.90	$ 2.97

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 147,334	$ 129,488	$ 196,763
Other Comprehensive Income (Loss):
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes of $888, $(1,095) and $(636), respectively	3,339	(4,119)	(2,393)
Total other comprehensive income (loss)	3,339	(4,119)	(2,393)
Comprehensive income	150,673	125,369	194,370
Comprehensive loss attributable to noncontrolling interests			216
Comprehensive income attributable to Avista Corporation shareholders	$ 150,673	$ 125,369	$ 194,586

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, after Reclassification Adjustment, Tax	$ 888	$ (1,095)	$ (636)

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 22,168	$ 14,196
Accounts and notes receivable, net	203,035	163,772
Materials and supplies, fuel stock and stored natural gas	84,733	67,451
Regulatory assets	43,783	13,673
Other current assets	80,754	84,885
Total current assets	434,473	343,977
Net utility property	5,225,515	4,991,612
Goodwill	52,426	52,426
Non-current regulatory assets	860,626	750,443
Other property and investments-net and other non-current assets	280,543	263,639
Total assets	6,853,583	6,402,097
Current Liabilities:
Accounts payable	133,096	106,613
Current portion of long-term debt	250,000	0
Short-term borrowings	284,000	203,000
Regulatory liabilities	77,149	46,435
Other current liabilities	168,861	149,831
Total current liabilities	913,106	505,879
Long-term debt	1,898,370	2,008,534
Long-term debt to affiliated trusts	51,547	51,547
Pensions and other postretirement benefits	153,467	211,880
Deferred income taxes	642,709	594,712
Non-current regulatory liabilities	861,515	784,820
Other non-current liabilities and deferred credits	178,125	214,999
Total liabilities	4,698,839	4,372,371
Commitments and Contingencies (See Notes to Consolidated Financial Statements)
Avista Corporation Shareholders’ Equity:
Common stock, no par value; 200,000,000 shares authorized; 71,497,523 and 69,238,901 shares issued and outstanding, respectively	1,380,152	1,286,068
Accumulated other comprehensive loss	(11,039)	(14,378)
Retained earnings	785,631	758,036
Total equity	2,154,744	2,029,726
Total liabilities and equity	$ 6,853,583	$ 6,402,097

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares, issued	71,497,523	69,238,901
Common stock, shares outstanding	71,497,523	69,238,901

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Net income	$ 147,334	$ 129,488	$ 196,763
Non-cash items included in net income:
Depreciation and amortization	232,176	224,223	205,994
Provision for deferred income taxes	11,224	44,964	15,098
Power and natural gas cost amortizations (deferrals), net	(51,847)	(9,923)	(45,917)
Amortization of debt expense	2,606	3,237	2,680
Amortization of investment in exchange power			1,633
Stock-based compensation expense	4,713	5,846	11,353
Equity-related AFUDC	(7,004)	(6,970)	(6,585)
Pension and other postretirement benefit expense	29,077	33,812	36,417
Other regulatory assets and liabilities and deferred debits and credits	676	10,287	65
Change in decoupling regulatory deferral	6,056	2,971	(10,327)
Realized and unrealized gain on assets and investments	(23,187)	(5,170)	(13,077)
Other	(2,859)	2,373	(7,899)
Contributions to defined benefit pension plan	(42,000)	(22,000)	(22,000)
Cash paid on settlement of interest rate swap agreements	(17,568)	(33,499)	(13,325)
Cash received on settlement of interest rate swap agreements	324
Changes in certain current assets and liabilities:
Accounts and notes receivable	(46,107)	(10,960)	(4,366)
Materials and supplies, fuel stock and stored natural gas	(17,282)	(868)	(6,148)
Collateral posted for derivative instruments	(17,564)	1,579	63,974
Income taxes receivable	20,199	(41,363)	(8,736)
Other current assets	930	(2,401)	(3,657)
Accounts payable	33,369	(10,152)	7,471
Other current liabilities	4,074	15,530	(1,199)
Net cash provided by operating activities	267,340	331,004	398,212
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(439,939)	(404,306)	(442,510)
Issuance of notes receivable	(1,841)	(4,393)	(7,303)
Equity and property investments	(16,001)	(5,925)	(13,508)
Proceeds from sale of investments	8,306	6,786	16,407
Other	(4,559)	(2,905)	1,403
Net cash used in investing activities	(444,916)	(410,743)	(445,511)
Financing Activities:
Net increase (decrease) in short-term borrowings	81,000	17,200	(4,200)
Proceeds from issuance of long-term debt	140,000	165,000	180,000
Maturity of long-term debt and finance leases	(2,935)	(54,800)	(92,660)
Issuance of common stock, net of issuance costs	89,998	72,200	64,573
Cash dividends paid	(118,211)	(110,254)	(102,772)
Other	(4,304)	(5,307)	(2,402)
Net cash provided by financing activities	185,548	84,039	42,539
Net increase (decrease) in cash and cash equivalents	7,972	4,300	(4,760)
Cash and cash equivalents at beginning of year	14,196	9,896	14,656
Cash and cash equivalents at end of year	22,168	14,196	9,896
Cash paid (received) during the year:
Interest	98,592	97,717	99,060
Income taxes paid	3,652	1,901	26,764
Income tax refunds	(22,330)	(918)	(979)
Non-cash financing and investing activities:
Accounts payable for capital expenditures	$ 23,938	$ 32,039	$ 25,644

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]
Beginning Balance (in shares) at Dec. 31, 2018		65,688,356
Shares issued through equity compensation plans		75,399
Shares issued through Employee Investment Plan (401-K)		3,653
Shares issued through sales agency agreements		1,409,588
Ending Balance (in shares) at Dec. 31, 2019		67,176,996
Beginning Balance at Dec. 31, 2018		$ 1,136,491	$ (7,866)	$ 644,595
Equity compensation expense		10,568
Issuance of common stock through equity compensation plans		827
Issuance of common stock through Employee Investment Plan (401-K)		175
Issuance of common stock through sales agency agreements, net of issuance costs		63,571
Payment of minimum tax withholdings for share-based payment awards		(891)
Ending Balance at Dec. 31, 2019	$ 1,939,284	$ 1,210,741	(10,259)	738,802
Other comprehensive income (loss)	(2,393)		(2,393)
Net income attributable to Avista Corporation shareholders	196,979			196,979
Dividends on common stock				(102,772)
Beginning Balance Noncontrolling Interest at Dec. 31, 2018					$ 825
Net loss attributable to noncontrolling interests	$ 216				(216)
Deconsolidation of noncontrolling interests related to sale of METALfx					$ (609)
Dividends declared per common share	$ 1.55
Total Avista Corporation shareholders’ equity	$ 1,939,284
Shares issued through equity compensation plans		139,726
Shares issued through Employee Investment Plan (401-K)		17,179
Shares issued through sales agency agreements		1,905,000
Ending Balance (in shares) at Dec. 31, 2020	69,238,901	69,238,901
Equity compensation expense		$ 5,535
Issuance of common stock through equity compensation plans		965
Issuance of common stock through Employee Investment Plan (401-K)		674
Issuance of common stock through sales agency agreements, net of issuance costs		70,561
Payment of minimum tax withholdings for share-based payment awards		(2,408)
Ending Balance at Dec. 31, 2020	$ 2,029,726	$ 1,286,068	(14,378)	758,036
Other comprehensive income (loss)	(4,119)		(4,119)
Net income attributable to Avista Corporation shareholders	$ 129,488			129,488
Dividends on common stock				(110,254)
Dividends declared per common share	$ 1.62
Total Avista Corporation shareholders’ equity	$ 2,029,726
Shares issued through equity compensation plans		93,806
Shares issued through Employee Investment Plan (401-K)		14,480
Shares issued through sales agency agreements		2,150,336
Ending Balance (in shares) at Dec. 31, 2021	71,497,523	71,497,523
Equity compensation expense		$ 5,079
Issuance of common stock through equity compensation plans		931
Issuance of common stock through Employee Investment Plan (401-K)		610
Issuance of common stock through sales agency agreements, net of issuance costs		88,457
Payment of minimum tax withholdings for share-based payment awards		(993)
Ending Balance at Dec. 31, 2021	$ 2,154,744	$ 1,380,152	(11,039)	785,631
Other comprehensive income (loss)	3,339		$ (3,339)
Net income attributable to Avista Corporation shareholders	$ 147,334			147,334
Dividends on common stock				$ (119,739)
Dividends declared per common share	$ 1.69
Total Avista Corporation shareholders’ equity	$ 2,154,744

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 1. SUMMARY OF SIGNIF ICANT 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 24 for business segment information. See Note 26 for discussion of the sale of METALfx, which was an unregulated subsidiary of the Company. Basis of Reporting The consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants (see Note 8). Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported for assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates include: • determining the market value of energy commodity derivative assets and liabilities, • pension and other postretirement benefit plan obligations, • contingent liabilities, • goodwill impairment testing, • recoverability of regulatory assets, and • unbilled revenues. Changes in these estimates and assumptions are considered reasonably possible and may have a material effect on the consolidated financial statements and thus actual results could differ from the amounts reported and disclosed herein. Regulation The Company is subject to state regulation in Washington, Idaho, Montana, Oregon and Alaska. The Company is also subject to federal regulation primarily by the FERC, as well as various other federal agencies with regulatory oversight of particular aspects of its operations. Depreciation For utility operations, depreciation expense is estimated by a method of depreciation accounting utilizing composite rates for utility plant. Such rates are designed to provide for retirements of properties at the expiration of their service lives. For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31: 2021 2020 2019 Avista Utilities Ratio of depreciation to average depreciable property 3.54 % 3.43 % 3.28 % Alaska Electric Light and Power Company Ratio of depreciation to average depreciable property 2.77 % 2.77 % 2.48 % The average service lives for the following broad categories of utility plant in service are (in years): Avista Utilities Alaska Electric Light Electric thermal/other production 26 42 Hydroelectric production 81 42 Electric transmission 50 43 Electric distribution 39 40 Natural gas distribution property 44 N/A Other shorter-lived general plant 8 18 Allowance for Funds Used During Construction AFUDC represents the cost of both the debt and equity funds used to finance utility plant additions during the construction period. As prescribed by regulatory authorities, AFUDC is capitalized as a part of the cost of utility plant. The debt component of AFUDC is credited against total interest expense in the Consolidated Statements of Income in the line item “capitalized interest.” The equity component of AFUDC is included in the Consolidated Statements of Income in the line item “other income-net.” The Company is permitted, under established regulatory rate practices, to recover the capitalized AFUDC, and a reasonable return thereon, through its inclusion in rate base and the provision for depreciation after the related utility plant is placed in service. Cash inflow related to AFUDC does not occur until the related utility plant is placed in service and included in rate base. The WUTC and IPUC have authorized Avista Utilities to calculate AFUDC using its allowed rate of return. To the extent amounts calculated using this rate exceed the AFUDC amounts calculated using the FERC formula, Avista Utilities capitalizes the excess as a regulatory asset. The regulatory asset associated with plant in service is amortized over the average useful life of Avista Utilities' utility plant which is approximately 30 years. The regulatory asset associated with construction work in progress is not amortized until the plant is placed in service. The effective AFUDC rate was the following for the years ended December 31: 2021 2020 2019 Avista Utilities 7.19 % 7.25 % 7.39 % Alaska Electric Light and Power Company 8.90 % 8.04 % 8.96 % Income Taxes Deferred income tax assets represent future income tax deductions the Company expects to utilize in future tax returns to reduce taxable income. Deferred income tax liabilities represent future taxable income the Company expects to recognize in future tax returns. Deferred tax assets and liabilities arise when there are temporary differences resulting from differing treatment of items for tax and accounting purposes. A deferred income tax asset or liability is determined based on the enacted tax rates that will be in effect when the temporary differences between the financial statement carrying amounts and tax basis of existing assets and liabilities are expected to be reported in the Company’s consolidated income tax returns. The effect on deferred income taxes from a change in tax rates is recognized in income in the period that includes the enactment date unless a regulatory order specifies deferral of the effect of the change in tax rates over a longer period of time. The Company establishes a valuation allowance when it is more likely than not that all, or a portion, of a deferred tax asset will not be realized. Deferred income tax assets and liabilities and regulatory assets and liabilities are established for income tax benefits flowed through to customers. The Company's largest deferred income tax item is the difference between the book and tax basis of utility plant. This item results from the temporary difference on depreciation expense. In early tax years, this item is recorded as a deferred income tax liability that will eventually reverse and become subject to income tax in later tax years. The Company did no t incur any penalties on income tax positions in 2021, 2020 or 2019. The Company would recognize interest accrued related to income tax positions as interest expense and any penalties incurred as other operating expense. Stock-Based Compensation The Company currently issues three types of stock-based compensation awards - restricted shares, market-based awards and performance-based awards. Historically, these stock compensation awards have not been material to the Company's overall financial results. Compensation cost relating to share-based payment transactions is recognized in the Company’s financial statements based on the fair value of the equity instruments issued and recorded over the requisite service period. The Company recorded stock-based compensation expense (included in other operating expenses) and income tax benefits in the Consolidated Statements of Income of the following amounts for the years ended December 31 (dollars in thousands): 2021 2020 2019 Stock-based compensation expense $ 4,713 $ 5,846 $ 11,353 Income tax benefits 990 1,228 2,384 Excess tax expenses on settled share-based employee ( 909 ) ( 165 ) ( 612 ) Restricted share awards vest in equal thirds each year over 3 years and are payable in Avista Corp. common stock at the end of each year if the service condition is met. Restricted stock is valued at the close of market of the Company’s common stock on the grant date. Total Shareholder Return (TSR) awards are market-based awards and Cumulative Earnings Per Share (CEPS) awards are performance awards. Both types of awards vest after a period of 3 years and are payable in cash or Avista Corp. common stock at the end of the three-year period. The method of settlement is at the discretion of the Company and historically the Company has settled these awards through issuance of Avista Corp. common stock and intends to continue this practice. Both types of awards entitle the recipients to dividend equivalent rights, are subject to forfeiture under certain circumstances, and are subject to meeting specific market or performance conditions. Based on the level of attainment of the market or performance conditions, the amount of cash paid or common stock issued will range from 0 to 200 percent of the initial awards granted. Dividend equivalent rights are accumulated and paid out only on shares that eventually vest and have met the market and performance conditions. The Company accounts for both the TSR awards and CEPS awards as equity awards and compensation cost for these awards is recognized over the requisite service period, provided that the requisite service period is rendered. For TSR awards, if the market condition is not met at the end of the three-year service period, there will be no change in the cumulative amount of compensation cost recognized, since the awards are still considered vested even though the market metric was not met. For CEPS awards, at the end of the three-year service period, if the internal performance metric of cumulative earnings per share is not met, all compensation cost for these awards is reversed as these awards are not considered vested. The fair value of each TSR award is estimated on the date of grant using a statistical model that incorporates the probability of meeting the market targets based on historical returns relative to a peer group. The estimated fair value of the CEPS awards was estimated on the date of grant as the share price of Avista Corp. common stock on the date of grant. The following table summarizes the number of grants, vested and unvested shares, earned shares (based on market metrics), and other pertinent information related to the Company's stock compensation awards for the years ended December 31: 2021 2020 2019 Restricted Shares Shares granted during the year 62,594 45,540 50,061 Shares vested during the year 34,854 56,203 48,228 Unvested shares at end of year 96,127 71,706 93,351 Unrecognized compensation expense at end of year $ 2,215 $ 2,003 $ 2,054 TSR Awards TSR shares granted during the year 64,910 47,848 99,214 TSR shares vested during the year 77,174 71,299 106,858 TSR shares earned based on market metrics 58,652 — — Unvested TSR shares at end of year 107,854 122,133 178,035 Unrecognized compensation expense at end of year $ 2,653 $ 2,296 $ 3,377 CEPS Awards CEPS shares granted during the year 64,910 47,848 49,609 CEPS shares vested during the year 38,590 35,622 53,454 CEPS shares earned based on market metrics 26,627 63,763 106,908 Unvested CEPS shares at end of year 107,854 83,464 88,990 Unrecognized compensation expense at end of year $ 1,223 $ 1,090 $ 2,401 Outstanding restricted, TSR and CEPS share awards include a dividend component that is paid in cash. A liability for the dividends payable related to these awards is accrued as dividends are announced throughout the life of the award. As of December 31, 2021 and 2020, the Company had recognized a liability of $ 1.5 million an d $ 0.8 million, respectively, related to the dividend equivalents payable on the outstanding and unvested share grants. Other Income - Net Other income - net consisted of the following items for the years ended December 31 (dollars in thousands): 2021 2020 2019 Interest income $ ( 1,943 ) $ ( 1,952 ) $ ( 2,587 ) Interest on regulatory deferrals ( 1,206 ) ( 1,222 ) ( 1,460 ) Equity-related AFUDC ( 7,004 ) ( 6,970 ) ( 6,585 ) Non-service portion of pension and other postretirement benefit 1,386 6,433 8,899 Earnings on investments ( 21,402 ) ( 905 ) ( 14,299 ) Other expense (income) ( 3,129 ) ( 201 ) 1,104 Total $ ( 33,298 ) $ ( 4,817 ) $ ( 14,928 ) Earnings per Common Share Attributable to Avista Corporation Shareholders Basic earnings per common share attributable to Avista Corp. shareholders is computed by dividing net income attributable to Avista Corp. shareholders by the weighted-average number of common shares outstanding for the period. Diluted earnings per common share attributable to Avista Corp. shareholders is calculated by dividing net income attributable to Avista Corp. shareholders by diluted weighted-average common shares outstanding during the period, including common stock equivalent shares outstanding using the treasury stock method, unless such shares are anti-dilutive. Common stock equivalent shares include shares issuable under contingent stock awards. See Note 21 for earnings per common share calculations. Cash and Cash Equivalents For the purposes of the Consolidated Statements of Cash Flows, the Company considers all temporary investments with a maturity of three months or less when purchased to be cash equivalents. Allowance for Doubtful Accounts The Company maintains an allowance for doubtful accounts to provide for estimated and potential losses on accounts receivable. The Company determines the allowance for utility and other customer accounts receivable based on historical write-offs as compared to accounts receivable and operating revenues. Additionally, the Company establishes specific allowances for certain individual accounts. The following table presents the activity in the allowance for doubtful accounts during the years ended December 31 (dollars in thousands): 2021 2020 2019 Allowance as of the beginning of the year $ 11,387 $ 2,419 $ 5,233 Additions expensed during the year (1) 9,279 11,280 460 Net deductions (2) ( 10,201 ) ( 2,312 ) ( 3,274 ) Allowance as of the end of the year $ 10,465 $ 11,387 $ 2,419 (1) Increases in 2021 and 2020 related to COVID-19 bad debt expense in excess of the amount recovered through rates. (2) Increase in 2021 relates to COVID forgiveness program. Utility Plant in Service The cost of additions to utility plant in service, including an allowance for funds used during construction and replacements of units of property and improvements, is capitalized. The cost of depreciable units of property retired plus the cost of removal less salvage is charged to accumulated depreciation. Asset Retirement Obligations The Company records the fair value of a liability for an ARO in the period in which it is incurred. When the liability is initially recorded, the associated costs of the ARO are capitalized as part of the carrying amount of the related long-lived asset. The liability is accreted to its present value each period and the related capitalized costs are depreciated over the useful life of the related asset. In addition, if there are changes in the estimated timing or estimated costs of the AROs, adjustments are recorded during the period new information becomes available as an increase or decrease to the liability, with the offset recorded to the related long-lived asset. Upon retirement of the asset, the Company either settles the ARO for its recorded amount or recognizes a regulatory asset or liability for the difference, which will be surcharged/refunded to customers through the ratemaking process. The Company records regulatory assets and liabilities for the difference between asset retirement costs currently recovered in rates and AROs recorded since asset retirement costs are recovered through rates charged to customers (see Note 10 for further discussion of the Company's AROs). The Company recovers certain asset retirement costs through rates charged to customers as a portion of its depreciation expense for which the Company has not recorded asset retirement obligations. The Company has recorded the amount of estimated retirement costs collected from customers (that do not represent legal or contractual obligations) and included them as a non-current regulatory liability on the Consolidated Balance Sheets in the following amounts as of December 31 (dollars in thousands): 2021 2020 Regulatory liability for utility plant retirement costs $ 350,190 $ 325,832 Goodwill Goodwill arising from acquisitions represents the future economic benefit arising from other assets acquired in a business combination that are not individually identified and separately recognized. The Company evaluates goodwill for impairment using a fair value to carrying amount comparison (Step 1). The Company completed its annual evaluation of goodwill for potential impairment as of November 30, 2021 and determined that goodwill was not impaired at that time (carrying value was less than the determined fair value). There were no events or circumstances that changed between November 30, 2021 and December 31, 2021 that would more likely than not reduce the fair values of the reporting units below their carrying amounts. There were no changes in the carrying amount of goodwill during 2020 and 2021, and the balance was as follows (dollars in thousands): AEL&P Accumulated Impairment Losses Total Balance as of December 31, 2020 and 2021 $ 52,426 $ - $ 52,426 Derivative Assets and Liabilities Derivatives are recorded as either assets or liabilities on the Consolidated Balance Sheets measured at estimated fair value. The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and costs result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rates 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 regulatory asset or liability is amortized as a component of interest expense over the term of the associated debt. The Company records an offset of interest rate swap derivative assets and liabilities with regulatory assets and liabilities, based on the prior practice of the commissions to provide recovery through the ratemaking process. 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 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 swap derivatives and foreign currency exchange derivatives, are reported at estimated fair value on the Consolidated Balance Sheets. See Note 18 for the Company’s fair value disclosures. Regulatory Deferred Charges and Credits The Company prepares its consolidated financial statements in accordance with regulatory accounting practices because: • rates for regulated services are established by or subject to approval by independent third-party regulators, • the regulated rates are designed to recover the cost of providing the regulated services, and • in view of demand for the regulated services and the level of competition, it is reasonable to assume that rates can be charged to and collected from customers at levels that will recover costs. Regulatory accounting practices require that certain costs and/or obligations (such as incurred power and natural gas costs not currently reflected in rates, but expected to be recovered or refunded in the future), are reflected as deferred charges or credits on the Consolidated Balance Sheets. These costs and/or obligations are not reflected in the Consolidated Statements of Income until the period during which matching revenues are recognized. The Company also has decoupling revenue deferrals. See Note 4 for discussion on decoupling revenue deferrals. If at some point in the future the Company determines that it no longer meets the criteria for continued application of regulatory accounting practices for all or a portion of its regulated operations, the Company could be: • required to write off its regulatory assets, and • precluded from the future deferral of costs or decoupled revenues not recovered through rates at the time such amounts are incurred, even if the Company expected to recover these amounts from customers in the future. See Note 23 for further details of regulatory assets and liabilities. Unamortized Debt Expense Unamortized debt expense includes debt issuance costs that are amortized over the life of the related debt. These costs are recorded as an offset to Long-Term Debt on the Consolidated Balance Sheets. Unamortized Debt Repurchase Costs Premiums paid or discounts received to repurchase debt are amortized over the remaining life of the original debt that was repurchased or, if new debt is issued in connection with the repurchase, these costs are amortized over the life of the new debt. These costs are recovered through retail rates as a component of interest expense. Appropriated Retained Earnings In accordance with the hydroelectric licensing requirements of section 10(d) of the Federal Power Act (FPA), the Company maintains an appropriated retained earnings account for any earnings in excess of the specified rate of return on the Company's investment in the licenses for its various hydroelectric projects. Per section 10(d) of the FPA, the Company must maintain these excess earnings in an appropriated retained earnings account until the termination of the licensing agreements or apply them to reduce the net investment in the licenses of the hydroelectric projects at the discretion of the FERC. The Company calculates the earnings in excess of the specified rate of return on an annual basis, usually during the second quarter. The appropriated retained earnings amounts included in retained earnings were as follows as of December 31 (dollars in thousands): 2021 2020 Appropriated retained earnings $ 53,620 $ 47,473 Contingencies The Company has unresolved regulatory, legal and tax issues which have inherently uncertain outcomes. The Company accrues a loss contingency if it is probable that a liability has been incurred and the amount of the loss or impairment can be reasonably estimated. The Company also discloses loss contingencies that do not meet these conditions for accrual, if there is a reasonable possibility that a material loss may be incurred. As of December 31, 2021 , the Company has not recorded any significant amounts related to unresolved contingencies. See Note 22 for further discussion of the Company's commitments and contingencies. COVID-19 In 2020, the WUTC, IPUC, and OPUC approved accounting orders that allow the Company to defer certain net COVID-19 related costs and benefits. As such, as of December 31, 2021, the Company has deferred net costs of $ 1.1 million for all jurisdictions. The respective regulatory authorities will determine the appropriateness and prudency of any deferred expenses when the Company seeks recovery. See “Regulatory Deferred Charges and Credits”.

New Accounting Standards

New Accounting Standards	12 Months Ended
	Dec. 31, 2021
Accounting Standards Update and Change in Accounting Principle [Abstract]
New Accounting Standards	NOTE 2. NEW ACCO UNTING STANDARDS 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 no t have a material impact on the Company's fair value disclosures. See Note 18 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 became effective for periods ending after December 15, 2020 and the requirements of this ASU did no t have a material impact on the Company’s disclosures upon adoption.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	NOTE 3. 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 regulated operations and the lower of cost or market for non-regulated operations and consisted of the following as of December 31 (dollars in thousands): 2021 2020 Materials and supplies $ 62,003 $ 53,258 Fuel stock 5,126 4,658 Stored natural gas 17,604 9,535 Total $ 84,733 $ 67,451 Other Current Assets Other current assets consisted of the following as of December 31 (dollars in thousands): 2021 2020 Collateral posted for derivative instruments after netting with outstanding $ 21,477 $ 4,336 Prepayments 24,387 24,411 Income taxes receivable 29,615 49,814 Other 5,275 6,324 Total $ 80,754 $ 84,885 Other Property and Investments-Net and Other Non-Current Assets Other property and investments-net and other non-current assets consisted of the following as of December 31 (dollars in thousands): 2021 2020 Operating lease ROU assets $ 70,133 $ 71,891 Finance lease ROU assets 43,697 47,338 Non-utility property 20,033 19,508 Equity investments 91,057 59,318 Investment in affiliated trust 11,547 11,547 Notes receivable 14,949 14,454 Deferred compensation assets 9,513 9,174 Assets held for sale (1) — 3,462 Other 19,614 26,947 Total $ 280,543 $ 263,639 (1) The Company sold certain subsidiary assets associated with Steam Plant Square and Brew Pub during 2021. Other Current Liabilities Other current liabilities consisted of the following as of December 31 (dollars in thousands): 2021 2020 Accrued taxes other than income taxes $ 41,706 $ 45,099 Derivative liabilities 28,801 14,008 Employee paid time off accruals 27,741 26,495 Accrued interest 17,538 17,083 Pensions and other postretirement benefits 13,582 11,987 Other 39,493 35,159 Total $ 168,861 $ 149,831 Other Non-Current Liabilities and Deferred Credits Other non-current liabilities and deferred credits consisted of the following as of December 31 (dollars in thousands): 2021 2020 Operating lease liabilities $ 66,068 $ 67,716 Finance lease liabilities 45,730 48,815 Deferred investment tax credits 29,313 29,866 Asset retirement obligations 17,142 17,194 Derivative liabilities 4,525 37,427 Other 15,347 13,981 Total $ 178,125 $ 214,999

Revenue

Revenue	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Revenue	NOTE 4. 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. In addition, the sale of electricity and natural gas is governed by the various state utility commissions, which set rates, charges, terms and conditions of service, and prices. Collectively, these rates, charges, terms and conditions are included in a “tariff,” which governs all aspects of the provision of regulated services. Tariffs are only permitted to be changed through a rate-setting process involving an independent, third-party regulator empowered by statute to establish rates that bind customers. Thus, all regulated sales by the Company are conducted subject to the regulator-approved tariff. Tariff sales involve the current provision of commodity service (electricity and/or natural gas) to customers for a price that generally has a basic charge and a usage-based component. Tariff rates also include certain pass-through costs to customers such as natural gas costs, retail revenue credits and other miscellaneous regulatory items that do not impact net income, but can cause total revenue to fluctuate significantly up or down compared to previous periods. The commodity is sold and/or delivered to and consumed by the customer simultaneously, and the provisions of the relevant tariff determine the charges the Company may bill the customer, payment due date, and other pertinent rights and obligations of both parties. Generally, tariff sales do not involve a written contract. 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 Consolidated Statements of Income in the line item "Utility revenues, exclusive of alternative revenue programs." Unbilled Revenue from Contracts with Customers The determination of the volume of energy sales to individual customers is based on the reading of their meters, which occurs on a systematic basis throughout the month (once per month for each individual customer). At the end of each calendar month, the amount of energy delivered to customers since the date of the last meter reading is estimated and the corresponding unbilled revenue is estimated and recorded. The Company's estimate of unbilled revenue is based on: • the number of customers, • current rates, • meter reading dates, • actual native load for electricity, • actual throughput for natural gas, and • electric line losses and natural gas system losses. Any difference between actual and estimated revenue is automatically corrected in the following month when the actual meter reading and customer billing occurs. Accounts receivable includes unbilled energy revenues of the following amounts as of December 31 (dollars in thousands): 2021 2020 Unbilled accounts receivable $ 74,479 $ 71,258 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 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 Consolidated Statements of Income. The Company's decoupling mechanisms (also known as a FCA in Idaho) qualify as alternative revenue programs. Decoupling revenue deferrals are recognized in the Consolidated Statements of Income during the period they occur (i.e. during the period of revenue shortfall or excess due to fluctuations in customer usage), subject to certain limitations, and a regulatory asset or liability is established which will be surcharged or rebated to customers in future periods. GAAP requires that for 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 Consolidated Statements 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 which 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. The Company records alternative program revenues under the gross method, which is to amortize the decoupling regulatory asset/liability to the alternative revenue program line item on the Consolidated Statements of Income as it is collected from or refunded to customers. The cash passing between the Company and the customers is presented in revenue from contracts with customers since it is a portion of the overall tariff paid by customers. This method results in a gross-up to both revenue from contracts with customers and revenue from alternative revenue programs, but has a net zero impact on total revenue. Depending on whether the previous deferral balance being amortized was a regulatory asset or regulatory liability, and depending on the size and direction of the current year deferral of surcharges and/or rebates to customers, it could result in negative alternative revenue program revenue during the year. Derivative Revenue Most wholesale electric and natural gas transactions (including both physical and financial transactions), and the sale of fuel are considered derivatives, which are 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, sales of materials, late fees and other charges that do not represent contracts with customers. 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 years ended December 31 (dollars in thousands): 2021 2020 2019 Utility-related taxes $ 62,736 $ 59,319 $ 59,528 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 26 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. Other Revenue Other non-utility revenue primarily relates to rent revenue, which is scoped out of ASC 606; therefore, this revenue is presented separately from revenue from contracts with customers. 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. As of December 31, 2021, the Company estimates it had unsatisfied capacity performance obligations of $ 17.4 million, which will be recognized as revenue in future periods as the capacity is provided to the customers. These performance obligations are not reflected in the financial statements, as the Company has not received payment for these services. Disaggregation of Total Operating Revenue The following table disaggregates total operating revenue by segment and source for the years ended December 31 (dollars in thousands): 2021 2020 2019 Avista Utilities Revenue from contracts with customers $ 1,233,904 $ 1,157,746 $ 1,152,125 Derivative revenues 152,590 110,313 118,741 Alternative revenue programs ( 6,635 ) ( 3,814 ) 9,614 Deferrals and amortizations for rate refunds to customers 2,984 5,335 4,509 Other utility revenues 10,156 7,888 10,884 Total Avista Utilities 1,392,999 1,277,468 1,295,873 AEL&P Revenue from contracts with customers 45,051 42,624 36,779 Deferrals and amortizations for rate refunds to customers ( 190 ) ( 190 ) ( 190 ) Other utility revenues 505 375 676 Total AEL&P 45,366 42,809 37,265 Other Revenue from contracts with customers 2 564 11,286 Other revenues 569 1,050 1,198 Total Other 571 1,614 12,484 Total operating revenues $ 1,438,936 $ 1,321,891 $ 1,345,622 Utility Revenue from Contracts with Customers by Type and Service The following table disaggregates revenue from contracts with customers associated with the Company's electric operations for the years ended December 31 (dollars in thousands): 2021 2020 2019 Avista Utilities AEL&P Total Utility Avista Utilities AEL&P Total Utility Avista Utilities AEL&P Total Utility ELECTRIC OPERATIONS Revenue from Residential $ 394,717 $ 18,940 $ 413,657 $ 377,785 $ 18,618 $ 396,403 $ 369,102 $ 17,134 $ 386,236 Commercial and 326,173 25,861 352,034 303,972 23,754 327,726 317,589 19,391 336,980 Industrial 106,756 — 106,756 103,103 — 103,103 105,802 — 105,802 Public street and 7,472 250 7,722 7,303 252 7,555 7,448 254 7,702 Total retail 835,118 45,051 880,169 792,163 42,624 834,787 799,941 36,779 836,720 Transmission 21,005 — 21,005 18,236 — 18,236 18,180 — 18,180 Other revenue from 33,870 — 33,870 19,252 — 19,252 26,969 — 26,969 Total revenue $ 889,993 $ 45,051 $ 935,044 $ 829,651 $ 42,624 $ 872,275 $ 845,090 $ 36,779 $ 881,869 The following table disaggregates revenue from contracts with customers associated with the Company's natural gas operations for the years ended December 31 (dollars in thousands): 2021 2020 2019 Avista Utilities Avista Utilities Avista Utilities NATURAL GAS OPERATIONS Revenue from contracts with customers Residential $ 221,405 $ 213,612 $ 196,430 Commercial 100,819 94,937 92,168 Industrial and interruptible 7,796 7,128 5,263 Total retail revenue 330,020 315,677 293,861 Transportation 8,547 7,917 8,674 Other revenue from contracts with customers 5,344 4,501 4,500 Total revenue from contracts with customers $ 343,911 $ 328,095 $ 307,035

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	NOTE 5. LEASES ASC 842 , outlines a model for entities to use in accounting for leases. The core principle of the model is that an entity should recognize the ROU assets and liabilities that arise from leases on the balance sheet and depreciate or amortize the asset and liability over the term of the lease, as well as provide disclosure to enable users of the consolidated financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. Significant Judgments and Assumptions The Company determines if an arrangement is a lease, as well as its classification, at its inception. ROU assets represent the Company's right to use an underlying asset for the lease term, and lease liabilities represent the Company's obligation to make lease payments arising from the lease. Operating and finance lease ROU assets and lease liabilities are recognized at the commencement date of the agreement based on the present value of lease payments over the lease term. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date to determine the present value of lease payments. The implicit rate is used when it is readily determinable. The operating and finance lease ROU assets also include any lease payments made and exclude lease incentives, if any, that accrue to the benefit of the lessee. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Any difference between lease expense and cash paid for leased assets is recognized as a regulatory asset or regulatory liability. Description of Leases Operating Leases The Company's most significant operating lease is with the State of Montana associated with submerged land around the Company's hydroelectric facilities in the Clark Fork River basin, which expires in 2046 . The terms of this lease are subject to adjustment - depending on the outcome of ongoing litigation between the State of Montana and NorthWestern Energy. In addition, the State of Montana and Avista Corp. are engaged in litigation regarding lease terms, including how much money, if any, the State of Montana should return to Avista Corp. Amounts recorded for this lease are uncertain and amounts may change in the future depending on the outcome of the ongoing litigation. Any reduction in future lease payments or the return of previously paid amounts to Avista Corp. will be included in the future ratemaking process. In addition to the lease with the State of Montana, the Company also has other operating leases for land associated with its utility operations, as well as communication sites which support network and radio communications within its service territory. The Company's leases have remaining terms of 1 to 72 years . Most of the Company's leases include options to extend the lease term for periods of 5 to 50 years . Options are exercised at the Company's discretion. Certain of the Company's lease agreements include rental payments which are periodically adjusted over the term of the agreement based on the consumer price index. The Company's lease agreements do not include any material residual value guarantees or material restrictive covenants. Avista Corp. does not record leases with a term of 12 months or less in the Consolidated Balance Sheets. Total short-term lease costs for the year ended December 31, 2021 are immaterial. Finance Lease AEL&P has a PPA which is treated as a finance lease for accounting purposes related to the Snettisham hydroelectric project, which expires in 2034 . For ratemaking purposes, this lease is treated as an operating lease with a constant level of annual rental expense (straight line rent expense). Because of this regulatory treatment, any difference between the operating lease expense for ratemaking purposes and the expenses recognized under GAAP (interest expense and amortization of the finance lease ROU asset) is recorded as a regulatory asset and amortized during the later years of the lease when the finance lease expense is less than the operating lease expense included in base rates. The amortization of the ROU asset is included in depreciation and amortization and the interest associated with the lease liability is included in interest expense on the Consolidated Statements of Income. The components of lease expense were as follows for the year ended December 31 (dollars in thousands): 2021 2020 Operating lease cost: Fixed lease cost (Other operating expenses) $ 4,970 $ 4,746 Variable lease cost (Other operating expenses) 1,180 1,099 Total operating lease cost $ 6,150 $ 5,845 Finance lease cost: Amortization of ROU asset (Depreciation and amortization) $ 3,641 $ 3,641 Interest on lease liabilities (Interest expense) 2,522 2,662 Total finance lease cost $ 6,163 $ 6,303 Supplemental cash flow information related to leases was as follows for the year ended December 31 (dollars in thousands): 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflows: Operating lease payments $ 4,805 $ 4,612 Interest on finance lease 2,522 2,662 Total operating cash outflows $ 7,327 $ 7,274 Finance cash outflows: Principal payments on finance lease $ 2,935 $ 2,800 Supplemental balance sheet information related to leases was as follows for December 31 (dollars in thousands): December 31, December 31, 2021 2020 Operating Leases Operating lease ROU assets (Other property and investments-net $ 70,133 $ 71,891 Other current liabilities $ 4,301 $ 4,249 Other non-current liabilities and deferred credits 66,068 67,716 Total operating lease liabilities $ 70,369 $ 71,965 Finance Leases Finance lease ROU assets (Other property and investments-net $ 43,697 $ 47,338 Other current liabilities $ 3,085 $ 2,935 Other non-current liabilities and deferred credits 45,730 48,815 Total finance lease liabilities $ 48,815 $ 51,750 Weighted Average Remaining Lease Term Operating leases 24.22 years 25.20 years Finance leases 6.32 years 7.22 years Weighted Average Discount Rate Operating leases 4.28 % 4.28 % Finance leases 4.35 % 4.62 % Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2021 (dollars in thousands): Operating Leases Finance Leases 2022 $ 4,820 $ 5,460 2023 4,849 5,456 2024 4,875 5,459 2025 4,882 5,454 2026 4,867 5,456 Thereafter 91,845 38,204 Total lease payments $ 116,138 $ 65,489 Less: imputed interest ( 45,769 ) ( 16,674 ) Total $ 70,369 $ 48,815 Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2020 (dollars in thousands): Operating Leases Finance Leases 2021 $ 4,779 $ 5,457 2022 4,799 5,460 2023 4,827 5,456 2024 4,852 5,459 2025 4,865 5,454 Thereafter 96,734 43,661 Total lease payments $ 120,856 $ 70,947 Less: imputed interest ( 48,891 ) ( 19,197 ) Total $ 71,965 $ 51,750

Variable Interest Entities

Variable Interest Entities	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	NOTE 6. VARIABLE INTEREST ENTITIES Lancaster Power Purchase Agreement The Company has a PPA for the purchase of all the output of the Lancaster Plant, a 270 MW natural gas-fired combined cycle combustion turbine plant located in Kootenai County, Idaho, owned by an unrelated third-party (Rathdrum Power LLC), through 2026. Avista Corp. has a variable interest in the PPA. Accordingly, Avista Corp. made an evaluation of which interest holders have the power to direct the activities that most significantly impact the economic performance of the entity and which interest holders have the obligation to absorb losses or receive benefits that could be significant to the entity. Avista Corp. pays a fixed capacity and operations and maintenance payment and certain monthly variable costs under the PPA. Under the terms of the PPA, Avista Corp. makes the dispatch decisions, provides all natural gas fuel and receives all of the electric energy output from the Lancaster Plant. However, Rathdrum Power LLC (the owner) controls the daily operation of the Lancaster Plant and makes operating and maintenance decisions. Rathdrum Power LLC controls all of the rights and obligations of the Lancaster Plant after the expiration of the PPA in 2026 and Avista Corp. does not have any further obligations after the expiration. It is estimated that the plant will have 15 to 25 years of useful life after that time. Rathdrum Power LLC bears the maintenance risk of the plant and will receive the residual value of the Lancaster Plant. Avista Corp. has no debt or equity investments in the Lancaster Plant and does not provide financial support through liquidity arrangements or other commitments (other than the PPA). Based on its analysis, Avista Corp. does not consider itself to be the primary beneficiary of the Lancaster Plant. Accordingly, neither the Lancaster Plant nor Rathdrum Power LLC is included in Avista Corp.’s consolidated financial statements. The Company has a future contractual obligatio n of $ 143.4 million u nder the PPA (representing the fixed capacity and operations and maintenance payments through 2026) and believes this would be its maximum exposure to loss. However, the Company believes that such costs will be recovered through retail rates. Limited Partnerships and Similar Entities Under current GAAP, a limited partnership or similar legal entity that is the functional equivalent of a limited partnership is considered a VIE regardless of whether it otherwise qualifies as a voting interest entity unless a simple majority or lower threshold of the “unrelated” limited partners (i.e., parties other than the general partner, entities under common control with the general partner, and other parties acting on behalf of the general partner) have substantive kick-out rights (including liquidation rights) or participating rights. The Company has investments in limited partnerships (or the functional equivalent) where Avista Corp. is a limited partner investor in an investment fund where the general partner makes all of the investment and operating decisions with regards to the partnership and fund. To remove the general partner from any of the funds, approval from greater than a simple majority of the limited partners is required. As such, the limited partners do not have substantive kick-out rights and these investments are considered VIEs. Consolidation of these VIEs by Avista Corp. is not required because the Company does not have majority ownership in any of the funds, it does not have the power to direct any activities of the funds, and it does not have the power to appoint executive leadership, including the board of directors. Avista Corp. participates in profits and losses of the investment funds based on its ownership percentage and its losses are capped at its total initial investment in the funds. As of December 31, 2021 , Avista Corp. has invested $ 75.4 million in these investment funds, with an additional commitment of $ 27.0 million remaining to be invested. In addition, the Company is not allowed to withdraw any capital contributions from the investment funds until after the funds' expiration dates and all liabilities of the funds are settled. The expiration dates range from 2022 to 2040 , with three investments having no termination date (as they are perpetual). One of the funds is closed and expired and the Company is awaiting final distribution as soon as the underlying investments are liquidated. As of December 31, 2021 , the Company has a total carrying amount of $ 79.2 million in these investment funds.

Derivatives and Risk Management

Derivatives and Risk Management	12 Months Ended
	Dec. 31, 2021
Derivative Instruments and Hedges, Assets [Abstract]
Derivatives and Risk Management	NOTE 7. 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, the Company 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 mitigates the fixed costs. Avista Corp. also optimizes its natural gas storage capacity by purchasing and storing natural gas when prices are traditionally lower, typically in the summer, and withdrawing during higher priced months, typically during the winter. However, if market conditions and prices indicate that Avista Corp. should buy or sell natural gas at other times during the year, Avista Corp. engages in optimization transactions to capture value in the marketplace. Natural gas optimization activities include, but are not limited to, wholesale market sales of surplus natural gas supplies, purchases and sales of natural gas to optimize use of pipeline and storage capacity, and participation in the transportation capacity release market. The following table presents the underlying energy commodity derivative volumes as of December 31, 2021 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) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) 2022 129 — 7,114 61,405 234 452 3,933 31,485 2023 — — 378 23,218 — — 1,360 9,323 2024 — — 228 3,413 — — 1,370 228 2025 — — — — — — 1,115 — As of December 31, 2021 , there are no expected deliveries of energy commodity derivatives afte r 2 0 25. The following table presents the underlying energy commodity derivative volumes as of December 31, 2020 that were expected to be delivered in each respective year (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) 2021 1 224 10,353 65,188 17 451 5,448 39,273 2022 — — 450 25,525 — — 1,360 12,030 2023 — — — 4,950 — — 1,360 900 2024 — — — — — — 1,370 — 2025 — — — — — — 1,115 — As of December 31, 2020 , there were no expected deliveries of energy commodity derivatives after 2 0 25. (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 December 31 (dollars in thousands): 2021 2020 Number of contracts 25 22 Notional amount (in United States dollars) $ 8,571 $ 3,860 Notional amount (in Canadian dollars) 10,957 4,949 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 the balance sheet date indicated below (dollars in thousands): Balance Sheet Date Number of Contracts Notional Amount Mandatory Cash December 31, 2021 13 140,000 2022 2 20,000 2023 1 10,000 2024 December 31, 2020 4 45,000 2021 11 120,000 2022 1 10,000 2023 See Note 16 for discussion of the bond purchase agreement and the related settlement of interest rate swaps in connection with the pricing of the bonds in September 2021. The fair value of outstanding interest rate swap derivatives can vary significantly from period to period depending on the total notional amount of swap derivatives outstanding and fluctuations in market interest rates compared to the interest rates fixed by the swaps. Avista Corp. is required to make cash payments to settle the interest rate swap derivatives when the fixed rates are higher than prevailing market rates at the date of settlement. Conversely, Avista Corp. receives cash to settle its interest rate swap derivatives when prevailing market rates at the time of settlement exceed the fixed swap rates. Summary of Outstanding Derivative Instruments The amounts recorded on the Consolidated Balance Sheets as of December 31, 2021 and December 31, 2020 reflect the offsetting of derivative assets and liabilities where a legal right of offset exists. The following table presents the fair values and locations of derivative instruments recorded on the Consolidated Balance Sheets as of December 31, 2021 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Gross Collateral Net Asset Foreign currency exchange derivatives Other current liabilities $ — $ ( 19 ) $ — $ ( 19 ) Interest rate swap derivatives Other property and investments-net and other non-current assets 1,149 — — 1,149 Other current liabilities 1,170 ( 25,196 ) — ( 24,026 ) Other non-current liabilities and deferred credits — ( 78 ) — ( 78 ) Energy commodity derivatives Other current assets 1,506 ( 107 ) — 1,399 Other property and investments-net and other 6,844 ( 5,335 ) — 1,509 Other current liabilities 25,771 ( 39,616 ) 9,089 ( 4,756 ) Other non-current liabilities and deferred credits 141 ( 4,589 ) — ( 4,448 ) Total derivative instruments recorded on the $ 36,581 $ ( 74,940 ) $ 9,089 $ ( 29,270 ) The following table presents the fair values and locations of derivative instruments recorded on the Consolidated Balance Sheets as of December 31, 2020 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Gross Collateral Net Asset Foreign currency exchange derivatives Other current assets $ 30 $ — $ — $ 30 Interest rate swap derivatives Other current liabilities — ( 19,575 ) 8,050 ( 11,525 ) Other non-current liabilities and deferred credits 952 ( 32,190 ) — ( 31,238 ) Energy commodity derivatives Other current assets 9,203 ( 8,306 ) — 897 Other property and investments-net and other 1,755 ( 1,159 ) — 596 Other current liabilities 11,037 ( 14,007 ) 487 ( 2,483 ) Other non-current liabilities and deferred credits 1,725 ( 8,043 ) 129 ( 6,189 ) Total derivative instruments recorded on the $ 24,702 $ ( 83,280 ) $ 8,666 $ ( 49,912 ) 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 December 31 (in thousands): 2021 2020 Energy commodity derivatives Cash collateral posted $ 30,567 $ 4,953 Letters of credit outstanding 34,000 23,500 Balance sheet offsetting (cash collateral against net derivative positions) 9,089 616 Interest rate swap derivatives Cash collateral posted (offset by net derivative positions) — 8,050 There were no letters of credit outstanding related to interest rate swap derivatives as of December 31, 2021 and December 31, 2020. 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 December 31 (in thousands): 2021 2020 Interest rate swap derivatives Liabilities with credit-risk-related contingent features $ 25,274 $ 50,813 Additional collateral to post 25,274 42,763

Jointly Owned Electric Faciliti

Jointly Owned Electric Facilities	12 Months Ended
	Dec. 31, 2021
Jointly Owned Utility Plant, Net Ownership Amount [Abstract]
Jointly Owned Electric Facilities	NOTE 8. JOINTLY OWNED ELECTRIC FACILITIES The Company has a 15 percent ownership interest in Units 3 & 4 of the Colstrip generating station, a coal-fired plant located in southeastern Montana, and provides financing for its ownership interest in the project. Pursuant to the ownership and operating agreements among the co-owners, the Company’s share of related fuel costs as well as operating expenses for plant in service are included in the corresponding accounts in the Consolidated Statements of Income. The Company’s share of utility plant in service for Colstrip and accumulated depreciation (inclusive of the ARO assets and accumulated amortization) were as follows as of December 31 (dollars in thousands): 2021 2020 Utility plant in service $ 395,028 $ 391,922 Accumulated depreciation ( 302,220 ) ( 284,282 ) See Note 10 for further discussion of AROs. While the obligations and liabilities with respect to Colstrip are to be shared among the co-owners on a pro-rata basis, many of the environmental liabilities are joint and several under the law, so that if any co-owner failed to pay its share of such liability, the other co-owners (or any one of them) could be required to pay the defaulting co-owner‘s share (or the entire liability).

Property, Plant And Equipment

Property, Plant And Equipment	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	NOTE 9. PROPERTY, PLANT AND EQUIPMENT Net Utility Property Net utility property consisted of the following as of December 31 (dollars in thousands): 2021 2020 Utility plant in service $ 7,166,580 $ 6,809,797 Construction work in progress 205,405 175,767 Total 7,371,985 6,985,564 Less: Accumulated depreciation and amortization 2,146,470 1,993,952 Total net utility property $ 5,225,515 $ 4,991,612 Gross Property, Plant and Equipment The gross balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in thousands): 2021 2020 Avista Utilities: Electric production $ 1,494,371 $ 1,457,497 Electric transmission 945,624 862,987 Electric distribution 2,093,937 1,978,868 Electric construction work-in-progress (CWIP) and other 424,733 384,372 Electric total 4,958,665 4,683,724 Natural gas underground storage 55,684 53,351 Natural gas distribution 1,356,477 1,282,563 Natural gas CWIP and other 87,852 83,644 Natural gas total 1,500,013 1,419,558 Common plant (including CWIP) 740,339 712,609 Total Avista Utilities 7,199,017 6,815,891 AEL&P: Electric production 106,094 105,076 Electric transmission 22,691 22,419 Electric distribution 27,138 25,814 Electric CWIP and other 7,319 6,677 Electric total 163,242 159,986 Common plant 9,726 9,687 Total AEL&P 172,968 169,673 Total gross utility property 7,371,985 6,985,564 Other (1) 17,818 16,394 Total $ 7,389,803 $ 7,001,958 (1) Included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets. Accumulated depreciation was $ 2.3 million as of December 31, 2021 and $ 2.2 million as of December 31, 2020 for the other businesses.

Asset Retirement Obligations

Asset Retirement Obligations	12 Months Ended
	Dec. 31, 2021
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	NOTE 10. ASSET RETI REMENT OBLIGATIONS The Company has recorded liabilities for future AROs to: • restore coal ash containment ponds and coal holding areas at Colstrip, • cap a landfill at the Kettle Falls Plant, and • remove plant and restore the land at the Coyote Springs 2 site at the termination of the land lease. Due to an inability to estimate a range of settlement dates, the Company cannot estimate a liability for the: • removal and disposal of certain transmission and distribution assets, and • abandonment and decommissioning of certain hydroelectric generation and natural gas storage facilities. In 2015, the EPA issued a final rule regarding CCRs. Colstrip produces this byproduct. The CCR rule has been the subject of ongoing litigation. In August 2018, the D.C. Circuit struck down provisions of the rule. The rule includes technical requirements for CCR landfills and surface impoundments. The Colstrip owners developed a multi-year compliance plan to address the CCR requirements and existing state obligations. The actual asset retirement costs related to the CCR rule requirements may vary substantially from the estimates used to record the ARO due to the uncertainty and evolving nature of the compliance strategies that will be used and the availability of data used to estimate costs, such as the quantity of coal ash present at certain sites and the volume of fill that will be needed to cap and cover certain impoundments. The Company updates its estimates as new information becomes available. The Company expects to seek recovery of any increased costs related to complying with the CCR rule through the ratemaking process. In addition to the above, under a 2018 Administrative Order on Consent and ongoing negotiations with the Montana Department of Ecological Quality, the owners of Colstrip are required to provide financial assurance, primarily in the form of surety bonds, to secure each owner's pro-rata share of various anticipated closure and remediation of the ash ponds and coal holding areas. The amount of financial assurance required of each owner may, like the ARO, vary substantially due to the uncertainty and evolving nature of anticipated closure and remediation activities, and as those activities are completed over time. The following table documents the changes in the Company’s asset retirement obligation during the years ended December 31 (dollars in thousands): 2021 2020 2019 Asset retirement obligation at beginning of year $ 17,194 $ 20,338 $ 18,266 Liabilities incurred 825 ( 2,315 ) 2,699 Liabilities settled ( 1,541 ) ( 1,645 ) ( 1,503 ) Accretion expense 664 816 876 Asset retirement obligation at end of year $ 17,142 $ 17,194 $ 20,338

Pension Plans and Other Postret

Pension Plans and Other Postretirement Benefit Plans	12 Months Ended
	Dec. 31, 2021
Retirement Benefits, Description [Abstract]
Pension Plans and Other Postretirement Benefit Plans	NOTE 11. PENSION PLANS AND OTHE R POSTRETIREMENT BENEFIT PLANS The pension and other postretirement benefit plans described below only relate to Avista Utilities. AEL&P (not discussed below) participates in a defined contribution multiemployer plan for its union workers and a defined contribution money purchase pension plan for its nonunion workers. None of the subsidiary retirement plans, individually or in the aggregate, are significant to Avista Corp. Avista Utilities The Company has a defined benefit pension plan covering the majority of all regular full-time employees at Avista Utilities that were hired prior to January 1, 2014. Employees eligible for the plan continue to accrue benefits. Individual benefits under this plan are based upon the employee’s years of service, date of hire and average compensation as specified in the plan. Non-union employees hired on or after January 1, 2014 participate in a defined contribution 401(k) plan in lieu of a defined benefit pension plan. Union employees hired on or after January 1, 2014 are still covered under the defined benefit pension plan. 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 $ 42.0 million in cash to the pension plan in 2021 , and $ 22.0 million in 2020 and 2019 . The Company expects to contribute $ 42.0 million in cash to the pension plan in 2022. The Company also has a SERP that provides additional pension benefits to certain executive officers and certain key employees of the Company. The SERP is intended to provide benefits to individuals whose benefits under the defined benefit pension plan are reduced due to the application of Section 415 of the Internal Revenue Code of 1986 and the deferral of salary under deferred compensation plans. The liability and expense for this plan are included as pension benefits in the tables included in this Note. The Company expects that benefit payments under the pension plan and the SERP will total (dollars in thousands): 2022 2023 2024 2025 2026 Total 2027- Expected benefit payments $ 43,282 $ 43,218 $ 43,675 $ 44,319 $ 43,810 $ 228,585 The expected long-term rate of return on plan assets is based on past performance and economic forecasts for the types of investments held by the plan. In selecting a discount rate, the Company considers yield rates for highly rated corporate bond portfolios with maturities similar to that of the expected term of pension benefits. The Company provides certain health care and life insurance benefits for eligible retired employees that were hired prior to January 1, 2014. The Company accrues the estimated cost of postretirement benefit obligations during the years that employees provide services. The liability and expense of this plan are included as other postretirement benefits. Non-union employees hired on or after January 1, 2014, will have access to the retiree medical plan upon retirement; however, Avista Corp. will no longer provide a contribution toward their medical premium. The Company has a Health Reimbursement Arrangement (HRA) to provide employees with tax-advantaged funds to pay for allowable medical expenses upon retirement. The amount earned by the employee is fixed on the retirement date based on the employee’s years of service and the ending salary. The liability and expense of the HRA are included as other postretirement benefits. The Company provides death benefits to beneficiaries of executive officers who die during their term of office or after retirement. Under the plan, an executive officer’s designated beneficiary will receive a payment equal to twice the executive officer’s annual base salary at the time of death (or if death occurs after retirement, a payment equal to twice the executive officer’s total annual pension benefit). The liability and expense for this plan are included as other postretirement benefits. The Company expects that benefit payments under other postretirement benefit plans will total (dollars in thousands): 2022 2023 2024 2025 2026 Total 2027- Expected benefit payments $ 6,960 $ 7,140 $ 7,291 $ 7,453 $ 7,560 $ 39,646 The Company expects to contri bute $ 7.2 million t o other postretirement benefit plans in 2022, representing expected benefit payments to be paid during the year excluding the Medicare Part D subsidy. The Company uses a December 31 measurement date for its pension and other postretirement benefit plans. The following table sets forth the pension and other postretirement benefit plan disclosures as of December 31, 2021 and 2020 and the components of net periodic benefit costs for the years ended December 31, 2021, 2020 and 2019 (dollars in thousands): Pension Benefits Other Post- 2021 2020 2021 2020 Change in benefit obligation: Benefit obligation as of beginning of year $ 826,915 $ 742,382 $ 161,233 $ 159,296 Service cost 25,306 22,392 4,114 3,902 Interest cost 26,160 27,853 5,139 6,042 Actuarial (gain)/loss ( 13,997 ) 74,688 2,808 ( 2,589 ) Benefits paid ( 65,342 ) ( 40,400 ) ( 5,696 ) ( 5,418 ) Benefit obligation as of end of year $ 799,042 $ 826,915 $ 167,598 $ 161,233 Change in plan assets: Fair value of plan assets as of beginning of year $ 722,024 $ 642,063 $ 52,173 $ 44,853 Actual return on plan assets 50,370 96,591 7,371 7,320 Employer contributions 42,000 22,000 — — Benefits paid ( 63,431 ) ( 38,630 ) — — Fair value of plan assets as of end of year $ 750,963 $ 722,024 $ 59,544 $ 52,173 Funded status $ ( 48,079 ) $ ( 104,891 ) $ ( 108,054 ) $ ( 109,060 ) Amounts recognized in the Consolidated Balance Sheets: Other current liabilities $ ( 1,951 ) $ ( 1,943 ) $ ( 684 ) $ ( 669 ) Non-current liabilities ( 46,128 ) ( 102,948 ) ( 107,370 ) ( 108,391 ) Net amount recognized $ ( 48,079 ) $ ( 104,891 ) $ ( 108,054 ) $ ( 109,060 ) Accumulated pension benefit obligation $ 685,493 $ 710,023 Accumulated postretirement benefit obligation: For retirees $ 78,347 $ 75,876 For fully eligible employees $ 32,144 $ 32,097 For other participants $ 57,107 $ 53,260 Included in accumulated other comprehensive loss (income) (net of tax): Unrecognized prior service cost (credit) $ 1,699 $ 1,902 $ ( 2,741 ) $ ( 3,570 ) Unrecognized net actuarial loss 94,109 119,318 48,872 53,737 Total 95,808 121,220 46,131 50,167 Less regulatory asset ( 85,550 ) ( 108,301 ) ( 45,350 ) ( 48,708 ) Accumulated other comprehensive loss for unfunded benefit $ 10,258 $ 12,919 $ 781 $ 1,459 Pension Benefits Other Post- 2021 2020 2021 2020 Weighted-average assumptions as of December 31: Discount rate for benefit obligation 3.39 % 3.25 % 3.40 % 3.27 % Discount rate for annual expense 3.25 % 3.85 % 3.27 % 3.89 % Expected long-term return on plan assets 5.40 % 5.50 % 4.60 % 5.30 % Rate of compensation increase 4.66 % 4.74 % Medical cost trend pre-age 65 – initial 6.00 % 6.25 % Medical cost trend pre-age 65 – ultimate 5.00 % 5.00 % Ultimate medical cost trend year pre-age 65 2026 2026 Medical cost trend post-age 65 – initial 6.00 % 6.25 % Medical cost trend post-age 65 – ultimate 5.00 % 5.00 % Ultimate medical cost trend year post-age 65 2026 2026 Pension Benefits Other Post-retirement Benefits 2021 2020 2019 2021 2020 2019 Components of net periodic benefit cost: Service cost (a) $ 25,306 $ 22,392 $ 19,755 $ 4,114 $ 3,902 $ 3,006 Interest cost 26,160 27,853 28,417 5,139 6,042 5,598 Expected return on plan assets ( 39,088 ) ( 34,886 ) ( 31,763 ) ( 2,400 ) ( 2,377 ) ( 2,101 ) Amortization of prior service cost (credit) 257 257 257 ( 921 ) ( 958 ) ( 981 ) Net loss recognition 6,645 6,717 10,216 3,865 4,871 4,013 Net periodic benefit cost $ 19,280 $ 22,333 $ 26,882 $ 9,797 $ 11,480 $ 9,535 (a) 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. Plan Assets The Finance Committee of the Company’s Board of Directors approves investment policies, objectives and strategies that seek an appropriate return for the pension plan and other postretirement benefit plans and reviews and approves changes to the investment and funding policies. The Company has contracted with investment consultants who are responsible for monitoring the individual investment managers. The investment managers’ performance and related individual fund performance is periodically reviewed by an internal benefits committee and by the Finance Committee to monitor compliance with investment policy objectives and strategies. Pension plan assets are invested in mutual funds, trusts and partnerships that hold marketable debt and equity securities, real estate, and absolute return. In seeking to obtain a return that aligns with the funded status of the pension plan, the investment consultant recommends allocation percentages by asset classes. These recommendations are reviewed by the internal benefits committee, which then recommends their adoption by the Finance Committee. The Finance Committee has established target investment allocation percentages by asset classes and also investment ranges for each asset class. The target investment allocation percentages are typically the midpoint of the established range. The target investment allocation percentages by asset classes are indicated in the table below: 2021 2020 Equity securities 55 % 35 % Debt securities 40 % 49 % Real estate 5 % 7 % Absolute return 0 % 9 % The target investment allocation percentages were revised in the first quarter of 2021 and the pension plan assets were reinvested to move toward the new target investment allocation percentages. The target asset allocation percentages were modified to better align the asset allocations with the funded status of the pension plan. The fair value of pension plan assets invested in debt and equity securities was based primarily on fair value (market prices). The fair value of investment securities traded on a national securities exchange is determined based on the reported last sales price; securities traded in the over-the-counter market are valued at the last reported bid price. Investment securities for which market prices are not readily available or for which market prices do not represent the value at the time of pricing, the investment manager estimates fair value based upon other inputs (including valuations of securities that are comparable in coupon, rating, maturity and industry). Pension plan and other postretirement plan assets whose fair values are measured using net asset value (NAV) are excluded from the fair value hierarchy and are included as reconciling items in the tables below. The Company's investments in common/collective trusts have redemption limitations that permit quarterly redemptions following notice requirements of 45 to 60 days. Most of the Company's investments in closely held investments and partnership interests have redemption limitations that range from bi-monthly to semi-annually following redemption notice requirements of 60 to 90 days. One investment in a partnership has a lock-up for redemption currently expiring in 2022 and is subject to extension. The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of the pension plan’s assets measured and reported as of December 31, 2021 at fair value (dollars in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ — $ 6,259 $ — $ 6,259 Fixed income securities: U.S. government issues — 19,310 — 19,310 Corporate issues — 233,496 — 233,496 International issues — 34,270 — 34,270 Municipal issues — 18,558 — 18,558 Mutual funds: U.S. equity securities 236,552 — — 236,552 International equity securities 112,873 — — 112,873 Plan assets measured at NAV (not subject to hierarchy Common/collective trusts: Real estate — — — 31,040 Partnership/closely held investments: Absolute return (1) — — — 363 International equity securities — — — 50,427 Real estate — — — 7,815 Total $ 349,425 $ 311,893 $ — $ 750,963 The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of the pension plan’s assets measured and reported as of December 31, 2020 at fair value (dollars in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ — $ 3,309 $ — $ 3,309 Fixed income securities: U.S. government issues — 10,990 — 10,990 Corporate issues — 279,857 — 279,857 International issues — 39,634 — 39,634 Municipal issues — 22,431 — 22,431 Mutual funds: U.S. equity securities 146,375 — — 146,375 International equity securities 96,311 — — 96,311 Absolute return (1) 11,640 — — 11,640 Plan assets measured at NAV (not subject to hierarchy Common/collective trusts: Real estate — — — 29,532 Partnership/closely held investments: Absolute return (1) — — — 47,188 International equity securities — — — 26,760 Real estate — — — 7,997 Total $ 254,326 $ 356,221 $ — $ 722,024 (1) This category invests in multiple strategies to diversify risk and reduce volatility. The strategies include: (a) event driven, relative value, convertible, and fixed income arbitrage, (b) distressed investments, (c) long/short equity and fixed income and (d) market neutral strategies. The fair value of other postretirement plan assets invested in debt and equity securities was based primarily on market prices. The fair value of investment securities traded on a national securities exchange is determined based on the last reported sales price; securities traded in the over-the-counter market are valued at the last reported bid price. For investment securities for which market prices are not readily available, the investment manager will determine fair value based upon other inputs (including valuations of securities that are comparable in coupon, rating, maturity and industry). The target asset allocation was 60 percent equity securities and 40 percent debt securities in both 2021 and 2020. The fair value of other postretirement plan assets was determined as of December 31, 2021 and 2020. The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of other postretirement plan assets measured and reported as of December 31, 2021 at fair value (dollars in thousands): Level 1 Level 2 Level 3 Total Balanced index mutual fund (1) $ 59,545 $ — $ — $ 59,545 The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of other postretirement plan assets measured and reported as of December 31, 2020 at fair value (dollars in thousands): Level 1 Level 2 Level 3 Total Balanced index mutual fund (1) $ 52,173 $ — $ — $ 52,173 (1) The balanced index fund for 2021 and 2020 is a single mutual fund that includes a percentage of U.S. equity and fixed income securities and International equity and fixed income securities. 401(k) Plans and Executive Deferral Plan Avista Utilities has a salary deferral 401(k) plan that is a defined contribution plan and covers substantially all employees. Employees can make contributions to their respective accounts in the plans on a pre-tax basis up to the maximum amount permitted by law. The Company matches a portion of the salary deferred by each participant according to the schedule in the respective plan. Employer matching contributions were as follows for the years ended December 31 (dollars in thousands): 2021 2020 2019 Employer 401(k) matching contributions $ 11,671 $ 11,742 $ 10,412 The Company has an Executive Deferral Plan. This plan allows executive officers and other key employees the opportunity to defer until the earlier of their retirement, termination, disability or death, up to 75 percent of their base salary and/or up to 100 percent of their incentive payments. Deferred compensation funds are held by the Company in a Rabbi Trust. There were deferred compensation assets included in other property and investments-net and corresponding deferred compensation liabilities included in other non-current liabilities and deferred credits on the Consolidated Balance Sheets of the following amounts as of December 31 (dollars in thousands): 2021 2020 Deferred compensation assets and liabilities $ 9,513 $ 9,174

Accounting For Income Taxes

Accounting For Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Accounting for Income Taxes	NOTE 12. ACCOUNTIN G FOR INCOME TAXES Income Tax Expense Income tax expense consisted of the following for the years ended December 31 (dollars in thousands): 2021 2020 2019 Current income tax expense (benefit) $ 807 $ ( 37,913 ) $ 16,276 Deferred income tax expense 11,224 44,964 15,098 Total income tax expense $ 12,031 $ 7,051 $ 31,374 State income taxes do not represent a significant portion of total income tax expense on the Consolidated Statements of Income for any periods presented. A reconciliation of federal income taxes derived from the statutory federal tax rate of 21 percent applied to income before income taxes as set forth in the accompanying Consolidated Statements of Income is as follows for the years ended December 31 (dollars in thousands): 2021 2020 2019 Federal income taxes at statutory rates $ 33,467 21.0 % $ 28,673 21.0 % $ 47,909 21.0 % Increase (decrease) in tax resulting from: Tax effect of regulatory treatment of utility ( 13,820 ) ( 8.7 ) ( 12,893 ) ( 9.4 ) ( 9,967 ) ( 4.3 ) State income tax expense 1,385 0.8 814 0.6 1,465 0.6 Acquisition costs — — — — ( 1,712 ) ( 0.7 ) Flow through related to deduction of meters ( 8,678 ) ( 5.4 ) — — — — Non-plant excess deferred turnaround (2) — — ( 8,476 ) ( 6.2 ) ( 5,690 ) ( 2.5 ) Tax loss on sale of METALfx — — — — ( 1,272 ) ( 0.6 ) Customer refunds related to prior years at 35 percent — — ( 1,189 ) ( 0.9 ) — — Other ( 323 ) ( 0.2 ) 122 0.1 641 0.3 Total income tax expense $ 12,031 7.5 % $ 7,051 5.2 % $ 31,374 13.8 % (1) With the approval of the Idaho and Washington general rate cases in 2021, a change in tax methodology resulted in recognizing a flow through benefit related to meters and mixed service costs. (2) In March 2020, the WUTC approved an all-party settlement agreement related to electric tax benefits that were set aside for Colstrip in the 2020 general rate case order. In the approved settlement agreement, the parties agreed to utilize $ 10.9 million ($ 8.4 million when tax-effected) of the electric benefits to offset costs associated with accelerating the depreciation of Colstrip Units, to reflect a remaining useful life through December 31, 2025. In the second quarter of 2020, the Company recorded a one-time increase to depreciation expense with an offsetting decrease to income tax expense. In March 2019, the IPUC approved an all-party settlement agreement related to electric tax benefits that were set aside for Colstrip in the 2020 general rate case order. In the approved settlement agreement, the parties agreed to utilize $ 6.4 million ($ 5.1 million when tax-effected) of the electric benefits to offset costs associated with accelerating the depreciation of Colstrip, to reflect a remaining useful life through December 31, 2027. In the second quarter of 2019, the Company recorded a one-time increase to depreciation expense with an offsetting decrease to income tax expense. Deferred Income Taxes Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and tax credit carryforwards. The total net deferred income tax liability consisted of the following as of December 31 (dollars in thousands): 2021 2020 Deferred income tax assets: Regulatory liabilities $ 200,513 $ 179,871 Tax credits and NOL carryforwards 64,994 57,516 Provisions for pensions 25,650 37,501 Other 38,181 42,641 Total gross deferred income tax assets 329,338 317,529 Valuation allowances for deferred tax assets ( 9,626 ) ( 10,021 ) Total deferred income tax assets after valuation allowances 319,712 307,508 Deferred income tax liabilities: Utility property, plant, and equipment 688,856 666,639 Regulatory assets 264,978 232,697 Other 8,587 2,884 Total deferred income tax liabilities 962,421 902,220 Net long-term deferred income tax liability $ 642,709 $ 594,712 The realization of deferred income tax assets is dependent upon the ability to generate taxable income in future periods. The Company evaluated available evidence supporting the realization of its deferred income tax assets and determined it is more likely than not that deferred income tax assets will be realized. As of December 31, 2021 , the Company had $ 17.1 million of state tax credit carryforwards. Of the total amount, the Company believes that it is more likely than not that it will only be able to utilize $ 7.5 million of the state tax credits. As such, the Company has recorded a valuation allowance of $ 9.6 million against the state tax credit carryforwards and reflected the net amount of $ 7.5 million as an asset as of December 31, 2021. State tax credits expire from 2022 to 2035 . Status of Internal Revenue Service (IRS) and State Examinations The Company and its eligible subsidiaries file consolidated federal income tax returns. All tax years after 2017 are open for an IRS tax examination. The Company also files state income tax returns in certain jurisdictions, including Idaho, Oregon, Montana and Alaska. Subsidiaries are charged or credited with the tax effects of their operations on a stand-alone basis. The Idaho State Tax Commission is currently reviewing tax years 2014 through 2017. All tax years after 2017 are open for examination in Idaho, Oregon, Montana and Alaska. The Company believes that any open tax years for federal or state income taxes will not result in adjustments that would be significant to the consolidated financial statements.

Energy Purchase Contracts

Energy Purchase Contracts	12 Months Ended
	Dec. 31, 2021
Energy Purchase Contracts [Abstract]
Energy Purchase Contracts	NOTE 13. ENERGY P URCHASE CONTRACTS The below discussion only relates to Avista Utilities. The sole energy purchase contract at AEL&P is a PPA for the Snettisham hydroelectric project and it is accounted for as a lease. AEL&P does not have any other significant operating agreements or contractual obligations. See Note 5 for further discussion of the Snettisham PPA. Avista Utilities has contracts for the purchase of fuel for thermal generation, natural gas for resale and various agreements for the purchase or exchange of electric energy with other entities. The remaining term of the contracts range from one month to twenty-five years . Total expenses for power purchased, natural gas purchased, fuel for generation and other fuel costs, which are included in utility resource costs in the Consolidated Statements of Income, were as follows for the years ended December 31 (dollars in thousands): 2021 2020 2019 Utility power resources $ 431,199 $ 324,297 $ 376,769 The following table details Avista Utilities’ future contractual commitments for power resources (including transmission contracts) and natural gas resources (including transportation contracts) (dollars in thousands): 2022 2023 2024 2025 2026 Thereafter Total Power resources $ 198,052 $ 187,552 $ 200,693 $ 193,877 $ 184,230 $ 1,888,038 $ 2,852,442 Natural gas resources 87,228 66,508 42,581 36,423 32,094 382,981 647,815 Total $ 285,280 $ 254,060 $ 243,274 $ 230,300 $ 216,324 $ 2,271,019 $ 3,500,257 These energy purchase contracts were entered into as part of Avista Utilities’ obligation to serve its retail electric and natural gas customers’ energy requirements, including contracts entered into for resource optimization. As a result, these costs are recovered either through base retail rates or adjustments to retail rates as part of the power and natural gas cost deferral and recovery mechanisms. The above future contractual commitments for power resources include fixed contractual amounts related to the Company's contracts with certain PUDs to purchase portions of the output of certain generating facilities. Although Avista Utilities has no investment in the PUD generating facilities, the fixed contracts obligate Avista Utilities to pay certain minimum amounts whether or not the facilities are operating. The cost of power obtained under the contracts, including payments made when a facility is not operating, is included in utility resource costs in the Consolidated Statements of Income. The contractual amounts included above consist of Avista Utilities’ share of existing debt service cost and its proportionate share of the variable operating expenses of these projects. The minimum amounts payable under these contracts are based in part on the proportionate share of the debt service requirements of the PUD's revenue bonds for which the Company is indirectly responsible. The Company's total future debt service obligation associated with the revenue bonds outstanding at December 31, 2021 (principal and interest) w as $ 278.3 million. In addition, Avista Utilities has operating agreements, settlements and other contractual obligations related to its generating facilities and transmission and distribution services. The expenses associated with these agreements are reflected as other operating expenses in the Consolidated Statements of Income. The following table details future contractual commitments under these agreements (dollars in thousands): 2022 2023 2024 2025 2026 Thereafter Total Contractual obligations $ 28,912 $ 29,680 $ 30,471 $ 31,287 $ 32,127 $ 212,852 $ 365,329

Committed Lines of Credit

Committed Lines of Credit	12 Months Ended
	Dec. 31, 2021
Short-term Debt [Abstract]
Committed Lines of Credit	NOTE 14. COMMITTE D 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. In June 2021, the Company entered into an amendment to its committed line of credit that extends the expiration date to June 2026 , with the option to extend for an additional one year period (subject to customary conditions). 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. The committed line of credit agreement contains customary covenants and default provisions. The credit agreement has a covenant which does not permit the ratio of “consolidated total debt” to “consolidated total capitalization” of Avista Corp. to be greater than 65 percent at any time. As of December 31, 2021, the Company was in compliance with this covenant. Balances outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed lines of credit were as follows as of December 31 (dollars in thousands): 2021 2020 Balance outstanding at end of period $ 284,000 $ 102,000 Letters of credit outstanding at end of period $ 34,000 $ 27,618 Average interest rate at end of period 1.11 % 1.22 % As of December 31, 2021 and 2020, the borrowings outstanding under Avista Corp.'s committed line of credit were classified as short-term borrowings on the Consolidated Balance Sheets. AEL&P AEL&P has a committed line of credit in the amount of $ 25.0 million that expires in November 2024 . The committed line of credit is secured by non-transferable first mortgage bonds of AEL&P issued to the agent bank that would only become due and payable in the event, and then only to the extent, that AEL&P defaults on its obligations under the committed line of credit. The committed line of credit agreement contains customary covenants and default provisions. The credit agreement has a covenant which does not permit the ratio of “consolidated total debt at AEL&P” to “consolidated total capitalization at AEL&P,” including the impact of the Snettisham bonds to be greater than 67.5 percent at any time. As of December 31, 2021, AEL&P was in compliance with this covenant. As of December 31, 2021 , there were no borrowings under the AEL&P committed line of credit. As of December 31, 2020 , there was $ 1.0 million outstanding with an average interest rate of 1.65 percent.

Credit Agreement

Credit Agreement	12 Months Ended
	Dec. 31, 2021
Credit Agreement [Abstract]
Credit Agreement	NOTE 15. CREDI T AGREEMENT In April 2020, the Company entered into a Credit Agreement with various financial institutions, in the amount of $ 100 million. The Company borrowed the entire $ 100 million available under this agreement in April 2020 and repaid the outstanding balance in April 2021 .

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Long-Term Debt	NOTE 16. LON G-TERM DEBT The following details long-term debt outstanding as of December 31 (dollars in thousands): Maturity Description Interest 2021 2020 Avista Corp. Secured Long-Term Debt 2022 First Mortgage Bonds 5.13 % 250,000 250,000 2023 Secured Medium-Term Notes 7.18 %- 7.54 % 13,500 13,500 2028 Secured Medium-Term Notes 6.37 % 25,000 25,000 2032 Secured Pollution Control Bonds (1) (1) 66,700 66,700 2034 Secured Pollution Control Bonds (1) (1) 17,000 17,000 2035 First Mortgage Bonds 6.25 % 150,000 150,000 2037 First Mortgage Bonds 5.70 % 150,000 150,000 2040 First Mortgage Bonds 5.55 % 35,000 35,000 2041 First Mortgage Bonds 4.45 % 85,000 85,000 2044 First Mortgage Bonds 4.11 % 60,000 60,000 2045 First Mortgage Bonds 4.37 % 100,000 100,000 2047 First Mortgage Bonds 4.23 % 80,000 80,000 2047 First Mortgage Bonds 3.91 % 90,000 90,000 2048 First Mortgage Bonds 4.35 % 375,000 375,000 2049 First Mortgage Bonds 3.43 % 180,000 180,000 2050 First Mortgage Bonds 3.07 % 165,000 165,000 2051 First Mortgage Bonds 3.54 % 175,000 175,000 2051 First Mortgage Bonds (2) 2.90 % 140,000 — Total Avista Corp. secured long-term debt 2,157,200 2,017,200 Alaska Electric Light and Power Company Secured Long-Term Debt 2044 First Mortgage Bonds 4.54 % 75,000 75,000 Total secured long-term debt 2,232,200 2,092,200 Alaska Energy and Resources Company Unsecured Long-Term Debt 2024 Unsecured Term Loan 3.44 % 15,000 15,000 Total secured and unsecured long-term debt 2,247,200 2,107,200 Other Long-Term Debt Components Unamortized debt discount ( 632 ) ( 710 ) Unamortized long-term debt issuance costs ( 14,498 ) ( 14,256 ) Total 2,232,070 2,092,234 Secured Pollution Control Bonds held by Avista ( 83,700 ) ( 83,700 ) Current portion of long-term debt ( 250,000 ) — Total long-term debt $ 1,898,370 $ 2,008,534 (1) In December 2010, $ 66.7 million and $ 17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new variable rate bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Consolidated Balance Sheets. (2) In September 2021, the Company issued and sold $ 70.0 million of 2.90 percent first mortgage bonds due in 2051 pursuant to a bond purchase agreement with institutional investors in the private placement market. In December 2021, the Company issued and sold the remaining $ 70.0 million of bonds pursuant to the same agreement. The total net proceeds from the sale of the bonds were used to repay a portion of the outstanding balance under Avista Corp.'s $ 400.0 million committed line of credit. In connection with the pricing of the first mortgage bonds in September 2021, the Company cash settled four interest rate swap derivatives (notional aggregate amount of $ 45.0 million) and paid a net amount of $ 17.2 million. See Note 7 for a discussion of interest rate swap derivatives. The following table details future long-term debt maturities including long-term debt to affiliated trusts (see Note 17) (dollars in thousands): 2022 2023 2024 2025 2026 Thereafter Total Debt maturities $ 250,000 $ 13,500 $ 15,000 $ — $ — $ 1,936,547 $ 2,215,047 Substantially all of Avista Utilities' and AEL&P's owned properties are subject to the lien of their respective mortgage indentures. Under the Mortgages and Deeds of Trust (Mortgages) securing their first mortgage bonds (including secured medium-term notes), Avista Utilities and AEL&P may each issue additional first mortgage bonds under their specific mortgage in an aggregate principal amount equal to the sum of: • 66-2/3 percent of the cost or fair value (whichever is lower) of property additions of that entity which have not previously been made the basis of any application under that entity's Mortgage, or • an equal principal amount of retired first mortgage bonds of that entity which have not previously been made the basis of any application under that entity's Mortgage, or • deposit of cash. Avista Utilities and AEL&P may not individually issue any additional first mortgage bonds (with certain exceptions in the case of bonds issued on the basis of retired bonds) unless the particular entity issuing the bonds has “net earnings” (as defined in that entity's Mortgage) for any period of 12 consecutive calendar months out of the preceding 18 calendar months that were at least twice the annual interest requirements on all mortgage securities at the time outstanding, including the first mortgage bonds to be issued, and on all indebtedness of prior rank. As of December 31, 2021, property additions and retired bonds would have allowed, and the net earnings test would not have prohibited, the issuance of $ 1.8 billion in a n aggregate principal amount of additional first mortgage bonds at Avista Utilitie s and $ 38.2 million b y AEL&P, at an assumed interest rate of 8 percent in each case.

Long- Term Debt to Affiliated T

Long- Term Debt to Affiliated Trust	12 Months Ended
	Dec. 31, 2021
Long Term Debt To Affiliated Trust [Abstract]
Long- Term Debt To Affiliated Trusts	NOTE 17. LONG-TERM DEB T 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 years ended December 31: 2021 2020 2019 Low distribution rate 0.99 % 1.10 % 2.79 % High distribution rate 1.10 % 2.79 % 3.61 % Distribution rate at the end of the year 1.05 % 1.10 % 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. These Preferred Trust Securities may be redeemed at the option of Avista Capital II at any time and mature on June 1, 2037. In December 2000, the Company purchased $ 10.0 million of these Preferred Trust Securities. The Company owns 100 percent of Avista Capital II and has solely and unconditionally guaranteed the payment of distributions on, and redemption price and liquidation amount for, the Preferred Trust Securities to the extent 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 Consolidated Balance Sheets. Interest expense to affiliated trusts in the Consolidated Statements of Income represents interest expense on these debentures.

Fair Value

Fair Value	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value	NOTE 18. F AIR VALUE The carrying values of cash and cash equivalents, accounts and notes receivable, accounts payable and short-term borrowings are reasonable estimates of their fair values. Long-term debt (including current portion), finance leases, and long-term debt to affiliated trusts are reported at carrying value on the Consolidated Balance Sheets. The fair value hierarchy prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to fair values derived from unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are defined as follows: Level 1 – Quoted prices are available in active markets for identical assets or liabilities. Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 – Pricing inputs are other than quoted prices in active markets included in Level 1, but which are either directly or indirectly observable as of the reporting date. Level 2 includes 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 Consolidated Balance Sheets as of December 31 (dollars in thousands): 2021 2020 Carrying Estimated Carrying Estimated Long-term debt (Level 2) $ 963,500 $ 1,157,651 $ 963,500 $ 1,189,824 Long-term debt (Level 3) 1,200,000 1,366,619 1,060,000 1,235,248 Snettisham finance lease obligation (Level 3) 48,815 54,000 51,750 58,700 Long-term debt to affiliated trusts (Level 3) 51,547 43,299 51,547 43,815 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 84.0 to 140.27 , where a par value of 100.00 represents the carrying value recorded on the Consolidated Balance Sheets. Level 2 long-term debt represents publicly issued bonds with quoted market prices; however, due to their limited trading activity, they are classified as Level 2 because brokers must generate quotes and make estimates using comparable debt with similar risk and terms if there is no trading activity near a period end. Level 3 long-term debt consists of private placement bonds and debt to affiliated trusts, which typically have no secondary trading activity. Fair values in Level 3 are estimated based on market prices from third party brokers using secondary market quotes for debt with similar risk and terms to generate quotes for Avista Corp. bonds. Due to the unique nature of the Snettisham finance lease obligation, the estimated fair value of these items was determined based on a discounted cash flow model using available market information. The Snettisham finance lease obligation was discounted to present value using the Morgan Markets A Ex-Fin discount rate as published on December 31, 2021. The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Consolidated Balance Sheets as of December 31, 2021 at fair value on a recurring basis (dollars in thousands): Level 1 Level 2 Level 3 Counterparty Total December 31, 2021 Assets: Energy commodity derivatives $ — $ 34,119 $ — $ ( 31,211 ) $ 2,908 Level 3 energy commodity derivatives: Natural gas exchange agreements — — 143 ( 143 ) — Interest rate swap derivatives — 2,319 — ( 1,170 ) 1,149 Deferred compensation assets: Mutual Funds: Fixed income securities (2) 1,809 — — — 1,809 Equity securities (2) 7,594 — — — 7,594 Total $ 9,403 $ 36,438 $ 143 $ ( 32,524 ) $ 13,460 Liabilities: Energy commodity derivatives $ — $ 41,733 $ — $ ( 40,300 ) $ 1,433 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 7,914 ( 143 ) 7,771 Foreign currency exchange derivatives — 19 — — 19 Interest rate swap derivatives — 25,274 — ( 1,170 ) 24,104 Total $ — $ 67,026 $ 7,914 $ ( 41,613 ) $ 33,327 The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Consolidated Balance Sheets as of December 31, 2020 at fair value on a recurring basis (dollars in thousands): Level 1 Level 2 Level 3 Counterparty Total December 31, 2020 Assets: Energy commodity derivatives $ — $ 23,645 $ — $ ( 22,152 ) $ 1,493 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 75 ( 75 ) — Foreign currency exchange derivatives — 30 — — 30 Interest rate swap derivatives — 952 — ( 952 ) — Deferred compensation assets: Mutual Funds: Fixed income securities (2) 2,471 — — — 2,471 Equity securities (2) 6,228 — — — 6,228 Total $ 8,699 $ 24,627 $ 75 $ ( 23,179 ) $ 10,222 Liabilities: Energy commodity derivatives $ — $ 23,030 $ — $ ( 22,768 ) $ 262 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 8,485 ( 75 ) 8,410 Interest rate swap derivatives — 51,765 — ( 9,002 ) 42,763 Total $ — $ 74,795 $ 8,485 $ ( 31,845 ) $ 51,435 (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 Consolidated Balance Sheets . The difference between the amount of derivative assets and liabilities disclosed in respective levels in the table above and the amount of derivative assets and liabilities disclosed on the Consolidated Balance Sheets is due to netting arrangements with certain counterparties. See Note 7 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 $ 0.1 million as of December 31, 2021 and $ 0.5 million as of December 31, 2020. Level 3 Fair Value For the natural gas commodity exchange agreement, the Company uses the same Level 2 brokered quotes described above; however, the Company also estimates the purchase and sales volumes (within contractual limits) as well as the timing of those transactions. Changing the timing of volume estimates changes the timing of purchases and sales, impacting which brokered quote is used. Because the brokered quotes can vary significantly from period to period, the unobservable estimates of the timing and volume of transactions can have a significant impact on the calculated fair value. The Company currently estimates volumes and timing of transactions based on a most likely scenario using historical data. Historically, the timing and volume of transactions have not been highly correlated with market prices and market volatility. The following table presents the quantitative information which was used to estimate the fair values of the Level 3 assets and liabilities above as of December 31, 2021 (dollars in thousands): Fair Value (Net) at December 31, 2021 Valuation Technique Unobservable Input Range Natural gas exchange ( 7,771 ) Internally derived Forward purchase prices $ 2.35 - $ 4.08 /mmBTU 2.96 Weighted Average Forward sales prices $ 2.38 - $ 9.50 /mmBTU 4.51 Weighted Average Purchase volumes 130,000 - 310,000 mmBTUs Sales volumes 25,000 - 310,000 mmBTUs The valuation methods, significant inputs and resulting fair values described above were developed by the Company's management and are reviewed on at least a quarterly basis to ensure they provide a reasonable estimate of fair value each reporting period. The following table presents activity for energy commodity derivative assets (liabilities) measured at fair value using significant unobservable inputs (Level 3) for the years ended December 31 (dollars in thousands): Natural Gas Power Total Year ended December 31, 2021: Balance as of January 1, 2021 $ ( 8,410 ) $ — $ ( 8,410 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets (1) 4,292 — 4,292 Settlements ( 3,653 ) — ( 3,653 ) Ending balance as of December 31, 2021 (2) $ ( 7,771 ) $ — $ ( 7,771 ) Year ended December 31, 2020: Balance as of January 1, 2020 $ ( 2,976 ) $ — $ ( 2,976 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets (1) ( 4,311 ) — ( 4,311 ) Settlements ( 1,123 ) — ( 1,123 ) Ending balance as of December 31, 2020 (2) $ ( 8,410 ) $ — $ ( 8,410 ) Year ended December 31, 2019: Balance as of January 1, 2019 $ ( 2,774 ) $ ( 2,488 ) $ ( 5,262 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets (1) 8,175 435 8,610 Settlements ( 8,377 ) 2,053 ( 6,324 ) Ending balance as of December 31, 2019 (2) $ ( 2,976 ) $ — $ ( 2,976 ) (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. Nonrecurring Fair Value Measurements The Company holds equity investments without a readily determinable fair value, and these assets are recorded at fair value and adjusted on a nonrecurring basis as a result of observable changes in fair value using the measurement alternative. Amounts recognized in the consolidated financial statements related to equity investments without readily determinable fair value include the following (dollars in thousands): December 31, 2021 December 31, 2020 Carrying Value (1) $ 24,161 $ 15,110 Gains (losses) 8,761 925 (1) Carrying value is adjusted to fair value as of the measurement date when observable changes in fair value occur, such as a transaction involving the underlying asset. These assets are measured using a market approach and are level 2 assets.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2021
Stockholders' Equity Note [Abstract]
Common Stock	NOTE 19. C OMMON STOCK The payment of dividends on common stock could be limited by: • certain covenants applicable to preferred stock (when outstanding) contained in the Company’s Restated Articles of Incorporation, as amended (currently there are no preferred shares outstanding), • certain covenants applicable to the Company's outstanding long-term debt and committed line of credit agreements, • the hydroelectric licensing requirements of section 10(d) of the FPA (see Note 1), and • certain requirements under the OPUC approval of the AERC acquisition in 2014. The OPUC's AERC acquisition order requires Avista Utilities to maintain a capital structure of no less than 35 percent common equity (inclusive of short-term debt). This limitation may be revised upon request by the Company with approval from the OPUC. The requirements of the OPUC approval of the AERC acquisition are the most restrictive. Under the OPUC restriction, the amount available for dividends at December 31, 2021 wa s $ 322.3 million . See the Consolidated Statements of Equity for dividends declared in the years 2019 through 2021. The Company has 10 million authorized shares of preferred stock. The Company did no t have any preferred stock outstanding as of December 31, 2021 and 2020. Common Stock Issuances The Company issued common stock in 2021 for total net proceeds of $ 90.0 million. Most of these issuances came through the Company's sales agency agreements under which the sales agents may offer and sell new shares of common stock from time to time. The Company has board and regulatory authority to issue a maximum of 4.3 million shares under these agreements, of which 2.1 million remain unissued as of December 31, 2021. In 2021, 2.2 million shares were issued under these agreements resulting in total net proceeds of $ 88.5 million.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2021
Accumulated Other Comprehensive Loss [Abstract]
Accumulated Other Comprehensive Loss	NOTE 20. ACCUMULATED O THER COMPREHENSIVE LOSS Accumulated Other Comprehensive Loss Accumulated other comprehensive loss, net of tax, consisted of the following as of December 31 (dollars in thousands): 2021 2020 Unfunded benefit obligation for pensions and other postretirement benefit 2,934 and $ 3,822 , respectively $ 11,039 $ 14,378 The following table details the reclassifications out of accumulated other comprehensive loss by component for the years ended December 31 (dollars in thousands): Amounts Reclassified from Accumulated Other Details about Accumulated Other Comprehensive Loss Components 2021 2020 2019 Amortization of defined benefit pension items Amortization of net prior service cost (a) $ ( 793 ) $ ( 794 ) $ ( 794 ) Amortization of net loss (a) 38,070 5,586 17,074 Adjustment due to effects of regulation (a) ( 33,050 ) ( 10,006 ) ( 19,309 ) Total before tax (b) 4,227 ( 5,214 ) ( 3,029 ) Tax expense (b) ( 888 ) 1,095 636 Net of tax (b) $ 3,339 $ ( 4,119 ) $ ( 2,393 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 11 for additional details). (b) Description is also the affected line item on the Consolidated Statements of Income

Earnings Per Common Share Attri

Earnings Per Common Share Attributable to Avista Corporation Shareholders	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Earnings Per Common Share Attributable to Avista Corporation Shareholders	NOTE 21. EARNINGS PER COMMON SHARE ATTRIB UTABLE TO AVISTA CORPORATION SHAREHOLDERS The following table presents the computation of basic and diluted earnings per common share attributable to Avista Corp. shareholders for the years ended December 31 (in thousands, except per share amounts): 2021 2020 2019 Numerator: Net income attributable to Avista Corp. shareholders $ 147,334 $ 129,488 $ 196,979 Denominator: Weighted-average number of common shares outstanding-basic 69,951 67,962 66,205 Effect of dilutive securities: Performance and restricted stock awards 134 140 124 Weighted-average number of common shares outstanding-diluted 70,085 68,102 66,329 Earnings per common share attributable to Avista Basic $ 2.11 $ 1.91 $ 2.98 Diluted $ 2.10 $ 1.90 $ 2.97 There were no shares excluded from the calculation because they were antidilutive.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 22. COMMITMENT S 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. Collective Bargaining Agreements The Company’s collective bargaining agreement with the IBEW represents approximately 40 percent of all of Avista Utilities’ employees. The Company’s largest represented group, representing approximately 90 percent of Avista Utilities' bargaining unit employees in Washington and Idaho, were covered under a three-year agreement which expired in March 2021. The Company is in the process of negotiating a new agreement with the IBEW. However, there is a risk that if a new agreement is not reached, employees subject to that agreement could strike. Given the number of employees that are covered by the collective bargaining agreement, a strike could result in disruptions to the Company's operations. However, the Company believes that the possibility of this occurring is remote. Boyds Fire (State of Washington Department of Natural Resources v. Avista) In August 2019, the Company was served with a complaint, captioned “State of Washington Department of Natural Resources v. Avista Corporation,” seeking recovery up to $ 4.4 million for fire suppression and investigation costs and related expenses incurred in connection with a wildfire that occurred in Ferry County, Washington in August 2018. Specifically, the complaint alleges 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 the tree before it 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. Additional lawsuits have subsequently been filed by private landowners seeking property damages, and holders of insurance subrogation claims seeking recovery of insurance proceeds paid. The lawsuits were filed in the Superior Court of Ferry County, Washington. The Company continues to vigorously defend itself in the litigation. However, the Company cannot predict the outcome of these matters. Labor Day Windstorm General In September 2020, a severe windstorm occurred in eastern Washington and northern Idaho. The extreme weather event resulted in customer outages and multiple wildfires in the region. The Company has become aware of instances where, during the course of the storm, otherwise healthy trees and limbs, located in areas outside its maintenance right-of-way, broke under the extraordinary wind conditions and caused damage to its energy delivery system at or near what is believed to be the potential area of origin of a wildfire. Those instances include what has been referred to as: the Babb Road fire (near Malden and Pine City, Washington); the Christensen Road fire (near Airway Heights, Washington); and the Mile Marker 49 fire (near Orofino, Idaho). These wildfires covered, in total, approximately 22,000 acres. The Company currently estimates approximately 230 residential, commercial and other structures were impacted. With respect to the Christensen Road Fire and the Mile Marker 49 Fire, the Company’s investigation determined that the primary cause of the fires was extreme high winds. To date, the Company has not found any evidence that the fires were caused by any deficiencies in its equipment, maintenance activities or vegetation management practices. See further discussion below regarding the Babb Road Fire. In addition to the instances identified above, the Company is aware of a 5-acre fire that occurred in Colfax, Washington, which damaged several residential structures. The Company’s investigation determined that the Company’s facilities were not involved in the ignition of this fire. The Company’s investigation has found no evidence of negligence with respect to any of the fires, and the Company intends to vigorously defend any claims for damages that may be asserted against it with respect to the wildfires arising out of the extreme wind event. Babb Road Fire On May 14, 2021 the Company learned that the Washington Department of Natural Resources (DNR) had completed its investigation and issued a report on the Babb Road Fire. The Babb Road fire covered approximately 15,000 acres and destroyed approximately 220 structures. There are no reports of personal injury or death resulting from the fire. The DNR report concluded, among other things, that • the fire was ignited when a branch of a multi-dominant Ponderosa Pine tree was broken off by the wind and fell on an Avista Corp. distribution line; • the tree was located approximately 30 feet from the center of Avista Corp.’s distribution line and approximately 20 feet beyond Avista Corp.’s right-of-way; • the tree showed some evidence of insect damage, damage at the top of the tree from porcupines, a small area of scarring where a lateral branch/leader (LBL) had broken off in the past, and some past signs of Gall Rust disease. The DNR report concluded as follows: “It is my opinion that because of the unusual configuration of the tree, and its proximity to the powerline, a closer inspection was warranted. A nearer inspection of the tree should have revealed the cut LBL ends and its previous failure, and necessitated determination of the failure potential of the adjacent LBL, implicated in starting the Babb Road Fire.” The DNR report acknowledged that, other than the multi-dominant nature of the tree, the conditions mentioned above would not have been easily visible without close-up inspection of, or cutting into, the tree. The report also acknowledged that, while the presence of multiple tops would have been visible from the nearby roadway, the tree did not fail at a v-fork due to the presence of multiple tops. The Company contends that applicable inspection standards did not require a closer inspection of the otherwise healthy tree, nor was the Company negligent with respect to its maintenance, inspection or vegetation management practices. The Company intends to vigorously defend any such assertion, if made. At this time, no material claims have been asserted against Avista Corp. for damages resulting from the Babb Road Fire. Colstrip Colstrip Owners Arbitration and Litigation Colstrip Units 3 & 4 are jointly owned by the Company, PSE, Pacificorp, PGE (collectively, the "Western Co-Owners"), as well as NorthWestern and Talen, and are operated pursuant to an Ownership and Operating Agreement dated May 6, 1981, as amended (O&O Agreement). Avista Corp. is a 15 percent owner in Units 3 & 4. No single owner owns more than 30 percent of either generating unit. The Washington CETA imposes deadlines by which coal-fired resources, such as Colstrip, must be excluded from the rate base of Washington utilities and by which electricity from such resources may no longer be delivered to Washington retail customers. The co-owners of Colstrip have differing needs for the generating capacity of these units. Accordingly, business disagreements have arisen among the co-owners, including, but not limited to, disagreements as to the shut-down date or dates of these units. These business disagreements, in turn, have led to disagreements as to the interpretation of the O&O Agreement, including, but not limited to, what percentage voting requirement under the O&O Agreement (55 percent vs. 100 percent) is needed to remove one or more of the Colstrip units from service or to make a determination that the project can no longer be operated consistent with prudent utility practice or the requirements of governmental agencies having jurisdiction. These disagreements are the subject of pending litigation in Montana Federal District Court in which the Western Co-Owners are plaintiffs and NorthWestern and Talen are defendants, as well as in the Montana District for Yellowstone County, in which Talen is the plaintiff and the Western Co-Owners and NorthWestern are defendants. In addition, there are legal proceedings pending in Montana Federal District Court with respect to the validity and constitutionality of changes to Montana law enacted in 2021 after the foregoing disputes arose. The Western Co-Owners are plaintiffs in those proceedings and NorthWestern and Talen are defendants. The changes to Montana law at issue purport to (a) dictate the location of any arbitration under the O&O Agreement, overriding the express provisions of that agreement; and (b) define actions relating to closing or not operating Colstrip as violations of Montana’s Consumer Protection Act. These legal proceedings remain pending. The Company is not able to predict the outcome, nor an amount or range of potential impact in the event of an outcome that is adverse to the Company’s interests. However, the Company will continue to vigorously defend and protect its interests (and those of its stakeholders) in all legal proceedings relating to Colstrip. Burnett et al. v. Talen et al. Multiple property owners have initiated a legal proceeding (titled Burnett et al. v. Talen et al. ) in the Montana District Court for Rosebud County against Talen, PSE, Pacificorp, PGE, Avista Corp., NorthWestern, and Westmoreland Rosebud Mining. The plaintiffs allege a failure to contain coal dust in connection with the operation of Colstrip, and seek unspecified damages. The Company will vigorously defend itself in the litigation, but at this time is unable to predict the outcome, nor an amount or range of potential impact in the event of an outcome that is adverse to the Company’s interests. Westmoreland Mine Permits Two lawsuits have been commenced by the Montana Environmental Information Center, challenging certain permits relating to the operation of the Westmoreland Rosebud Mine, which provides coal to Colstrip. The first, filed in the Montana District Court for Rosebud County, challenges the approval, by the Montana Board of Environmental Review, of a permit for mining what is designated as the “AM4” area of the mine, alleging procedural flaws in the approval process and substantive errors in its assessment of environmental impacts. On January 28, 2022, the Montana District Court for Rosebud County issued an order vacating the AM4 permit but deferring the annulment until April 1, 2022. The second proceeding, filed in the Montana Federal District Court, challenged the Office of Surface Mining Reclamation and Enforcement’s decision approving Westmoreland’s expansion of the mine into what is designated as “Area F” on the grounds that it violated the National Environmental Protection Act and the Endangered Species Act. On February 11, 2022, a Magistrate Judge issued findings and recommended that approval decision be vacated but that the annulment be delayed for 365 days from the date of a final order. Avista Corp. is not a party to either of these proceedings. Avista Corp. is continuing to monitor the progress of both lawsuits and assess the impact, if any, of the proceedings on Westmoreland’s ability to meet its contractual coal supply obligations. National Park Service (NPS) - Natural and Cultural Damage Claim In March 2017, the Company accessed property managed by the National Park Service (NPS) to prevent the imminent failure of a power pole that was surrounded by flood water in the Spokane River. The Company voluntarily reported its actions to the NPS several days later. Thereafter, in March 2018, the NPS notified the Company that it might seek recovery for unspecified costs and damages allegedly caused during the incident pursuant to the System Unit Resource Protection Act (SURPA), 54 U.S.C. 100721 et seq. In January 2021, the United States Department of Justice (DOJ) requested that the Company and the DOJ renew discussions relating to the matter. In July 2021, the DOJ communicated that it may seek damages of approximately $ 2 million in connection with the incident for alleged damage to "natural and cultural resources". In addition, the DOJ indicated that it may seek treble damages under the SURPA and state law, bringing its total potential claim to approximately $ 6 million. The Company disputes the position taken by the DOJ with respect to the incident, as well as the nature and extent of the DOJ’s alleged damages, and will vigorously defend itself in any litigation that may arise with respect to the matter. The Company and the DOJ have agreed to engage in discussions to understand their respective positions and determine whether a resolution of the dispute may be possible. However, the Company cannot predict the outcome of the matter. Rathdrum, Idaho Natural Gas Incident In October 2021, there was an incident in Rathdrum, Idaho involving the Company’s natural gas infrastructure. The incident occurred after a third party damaged those facilities during the course of excavation work. The incident resulted in a fire which destroyed one residence and resulted in minor injuries to the occupants. At this time, the Company is unable to predict the likelihood of a claim arising out of the matter, nor an amount or range of a potential loss, if any, in the event of such a claim. 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. The Company routinely assesses, based on studies, expert analysis and legal reviews, its contingencies, obligations and commitments for remediation of contaminated sites, including assessments of ranges and probabilities of recoveries from other responsible parties who either have or have not agreed to a settlement as well as recoveries from insurance carriers. The Company’s policy is to accrue and charge to current expense identified exposures related to environmental remediation sites based on estimates of investigation, cleanup and monitoring costs to be incurred. The Company has potential liabilities under the Endangered Species Act and similar state statutes for species of fish, plants and wildlife that have either already been added to the endangered species list, listed as “threatened” or petitioned for listing. Thus far, measures adopted and implemented have had minimal impact on the Company. However, the Company will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to these issues. Under the federal licenses for its hydroelectric projects, the Company is obligated to protect its property rights, including water rights. In addition, the Company holds additional non-hydro water rights. The State of Montana is examining the status of all water right claims within state boundaries through a general adjudication. Claims within the Clark Fork River basin could adversely affect the energy production of the Company’s Cabinet Gorge and Noxon Rapids hydroelectric facilities. The state of Idaho has initiated adjudication in northern Idaho, which will ultimately include the lower Clark Fork River, the Spokane River and the Coeur d’Alene basin. The Company is and will continue to be a participant in these and any other relevant adjudication processes. The complexity of such adjudications makes each unlikely to be concluded in the foreseeable future. As such, it is not possible for the Company to estimate the impact of any outcome at this time. The Company will continue to seek recovery, through the ratemaking process, of all costs related to this issue.

Regulatory Matters

Regulatory Matters	12 Months Ended
	Dec. 31, 2021
Regulated Operations [Abstract]
Regulatory Matters	NOTE 23. REGUL ATORY MATTERS Regulatory Assets and Liabilities The following table presents the Company’s regulatory assets and liabilities as of December 31, 2021 (dollars in thousands): Receiving 2021 2020 Remaining (1) Not (2) Current Non- Current Non- Regulatory Assets: Deferred income tax (3 ) $ 244,154 $ — $ — $ — $ 244,154 $ — $ 108,517 Pensions and other (4 ) — 165,696 — — 165,696 — 198,746 Energy commodity (5 ) — 15,385 — 12,447 2,938 2,073 5,722 Unamortized debt repurchase (6 ) 6,768 — — — 6,768 — 7,512 Settlement with 2059 38,926 — — — 38,926 — 40,043 Demand side management (3 ) — 3,974 — — 3,974 — 3,814 Decoupling surcharge 2023 24,532 — — 9,907 14,625 7,123 17,123 Utility plant to be abandoned (7 ) 26,771 — — — 26,771 — 28,916 Interest rate swaps (8 ) 158,082 — 41,672 — 199,754 — 214,851 Deferred power costs (3 ) 10,835 — — 7,334 3,501 1,775 1,562 Deferred natural gas costs (3 ) 21,027 — — 14,095 6,932 2,308 — AFUDC above FERC (11 ) 48,455 — — — 48,455 — 47,393 COVID-19 deferrals (12 ) — — 13,591 — 13,591 — 8,166 Advanced meter infrastructure (13 ) 36,008 — — — 36,008 — 26,379 Other regulatory assets (3 ) 37,045 8,563 2,925 — 48,533 394 41,699 Total regulatory assets $ 652,603 $ 193,618 $ 58,188 $ 43,783 $ 860,626 $ 13,673 $ 750,443 Regulatory Liabilities: Deferred natural gas costs (3 ) $ — $ — $ — $ — $ — $ 874 $ — Deferred power costs (3 ) 11,891 — — 6,457 5,434 20,299 17,570 Utility plant retirement costs (9 ) 350,190 — — — 350,190 — 325,832 Income tax related liabilities (3) (10) 346,847 24,411 143,862 56,331 458,789 14,952 399,677 Interest rate swaps (8 ) 13,589 — 1,473 — 15,062 — 15,046 Decoupling rebate 2022 9,308 — — 3,049 6,259 1,447 1,519 COVID-19 deferrals (12 ) — — 12,500 — 12,500 — 10,949 Other regulatory liabilities (3 ) 6,905 17,688 — 11,312 13,281 8,863 14,227 Total regulatory liabilities $ 738,730 $ 42,099 $ 157,835 $ 77,149 $ 861,515 $ 46,435 $ 784,820 (1) Earning a return includes either interest on the regulatory asset/liability or a return on the investment as a component of rate base at the allowed rate of return. (2) Expected recovery is pending regulatory treatment including regulatory assets and liabilities with prior regulatory precedence. (3) Remaining amortization period varies depending on timing of underlying transactions. (4) As the Company has historically recovered and currently recovers its pension and other postretirement benefit costs related to its regulated operations in retail rates, the Company records a regulatory asset for that portion of its pension and other postretirement benefit funding deficiency. (5) The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and losses result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho and periodic general rates cases. The resulting regulatory assets associated with energy commodity derivative instruments have been concluded to be probable of recovery through future rates. (6) Premiums paid or discounts received to repurchase debt are amortized over the remaining life of the original debt that was repurchased or, if new debt is issued in connection with the repurchase, these costs are amortized over the life of the new debt. These costs are recovered through retail rates as a component of interest expense. (7) The WUTC approved recovery of AMI project costs through the 2020 general rate case settlements, including amortization of retired meters replaced through the project through 2033. There are additional smaller projects included in the balance that the Company expects to fully recover, which have not yet been through the regulatory process. (8) For interest rate swap derivatives, Avista Corp. records all mark-to-market gains and losses in each accounting period as assets and liabilities, as well as offsetting regulatory assets and liabilities, such that there is no income statement impact. The interest rate swap derivatives are risk management tools similar to energy commodity derivatives. Upon settlement of interest rate swap derivatives, the regulatory asset or liability is amortized as a component of interest expense over the term of the associated debt. The Company records an offset of interest rate swap derivative assets and liabilities with regulatory assets and liabilities, based on the prior practice of the commissions to provide recovery through the ratemaking process. Settled interest rate swap derivatives which have been through a general rate case proceeding are classified as earning a return in the table above, whereas all unsettled interest rate swap derivatives and settled interest rate swap derivatives which have not been included in a general rate case are classified as expected recovery. (9) This amount is dependent upon the cost of removal of underlying utility plant assets and the life of utility plant. (10) The majority of this balance represents amounts due back to customers and resulted from the Tax Cuts and Jobs Act signed into law in December 2017, which changed the federal income tax rate from 35 percent to 21 percent. The Company revalued all deferred income taxes as of December 31, 2017. The Company expects the amounts for utility plant items for Avista Utilities to be returned to customers over a period of approximately 32 years . The Company expects the AEL&P amounts to be returned to customers over a period of approximately 40 years. A significant portion of the regulatory liability attributable to non-plant excess deferred taxes was used to offset a portion of the costs associated with accelerating the depreciation of Colstrip based on settlements in Washington and Idaho. (11) This amount is being amortized based on the underlying utility plant assets and the life of utility plant. (12) The WUTC, IPUC and OPUC issued accounting orders allowing the Company to defer certain costs, net of any benefits, related to the COVID-19 pandemic. The Company has recorded all benefits on a gross basis as a regulatory liability to customers and all additional allowed costs are a regulatory asset. The ratemaking treatment will be determined in future general rate cases in each jurisdiction. (13) This amount represents the deferral of the depreciation expense of the Company’s AMI project in Washington state. Recovery of these amounts was approved by WUTC in the 2021 general rate case order. Power Cost Deferrals and Recovery Mechanisms Deferred power supply costs are recorded as a deferred charge or liability on the Consolidated Balance Sheets for future prudence review and recovery or rebate through retail rates. The power supply costs deferred include certain differences between actual net power supply costs incurred by Avista Utilities and the costs included in base retail rates. This difference in net power supply costs primarily results from changes in: • short-term wholesale market prices and sales and purchase volumes, • the level, availability and optimization of hydroelectric generation, • the level and availability of thermal generation (including changes in fuel prices), • retail loads, and • sales of surplus transmission capacity. In Washington, the ERM allows Avista Utilities to periodically increase or decrease electric rates with WUTC approval to reflect changes in power supply costs. The ERM is an accounting method used to track certain differences between actual power supply costs, net of wholesale sales and sales of fuel, and the amount included in base retail rates for Washington customers and defer these differences (over the $ 4.0 million deadband and sharing bands) for future surcharge or rebate to customers. For 2021, the Company recognized a pre-tax expense o f $ 7.7 million under the ERM in Washington compared to a benefit of $ 6.2 million for 2020. Total net deferred power costs under the ERM were a liabil ity of $ 11.9 million as of December 31, 2021 and a liability of $ 37.9 million as of December 31, 2020 . These deferred power cost balances represent amounts due to customers. Pursuant to WUTC requirements, should the cumulative deferral balance exceed $ 30 million in the rebate or surcharge direction, the Company must make a filing with the WUTC to adjust customer rates to either return the balance to customers or recover the balance from customers. As the cumulative rebate balance exceeded $ 30 million, the Company’s 2019 filing contained a proposed rate refund. The ERM proceeding was considered with the Company’s 2019 general rate case proceeding and a refund was approved and is being returned to customers over a two-year period that began on April 1, 2020. Avista Utilities makes an annual filing on, or before, April 1 of each year to provide the opportunity for the WUTC staff and other interested parties to review the prudence of, and audit, the ERM deferred power cost transactions for the prior calendar year. Avista Utilities has a PCA mechanism in Idaho that allows it to modify electric rates on October 1 of each year with IPUC approval. Under the PCA mechanism, Avista Utilities defers 90 percent of the difference between certain actual net power supply expenses and the amount included in base retail rates for its Idaho customers. The October 1 rate adjustments recover or rebate power costs deferred during the preceding July-June twelve-month period. Total net power supply costs deferred under the PCA mechanism were an asset of $ 10.8 million as of December 31, 2021 and $ 2.5 million as of December 31, 2020. Deferred power cost assets represent amounts due from customers and liabilities represent amounts due to customers. Natural Gas Cost Deferrals and Recovery Mechanisms Avista Utilities files a PGA in all three states it serves to adjust natural gas rates for: 1) estimated commodity and pipeline transportation costs to serve natural gas customers for the coming year, and 2) the difference between actual and estimated commodity and transportation costs for the prior year. Total net deferred natural gas costs were an asset of $ 21.0 million as of December 31, 2021 and $ 1.4 million as of December 31, 2020. Asset balances represent amounts due from customers and liabilities represent amounts due to customers. Decoupling and Earnings Sharing Mechanisms Decoupling (also known as an FCA in Idaho) is a mechanism designed to sever the link between a utility's revenues and consumers' energy usage. In each of Avista Utilities' jurisdictions, Avista Utilities' electric and natural gas revenues are adjusted so as to be based on the number of customers in certain customer rate classes and assumed "normal" kilowatt hour and therm sales, rather than being based on actual kilowatt hour and therm sales. The difference between revenues based on the number of customers and "normal" sales and revenues based on actual usage is deferred and either surcharged or rebated to customers beginning in the following year. Only residential and certain commercial customer classes are included in decoupling mechanisms. Washington Decoupling and Earnings Sharing In Washington, the WUTC approved the Company's decoupling mechanisms for electric and natural gas for a five-year period beginning January 1, 2015. In 2019, the WUTC approved an extension of the mechanisms for an additional five-year term through March 31, 2025, with one modification in that new customers added after any test period would not be decoupled until included in a future test period. Electric and natural gas decoupling surcharge rate adjustments to customers are limited to a 3 percent increase on an annual basis, with any remaining surcharge balance carried forward for recovery in a future period. There is no limit on the level of rebate rate adjustments. The decoupling mechanisms each include an after-the-fact earnings test. At the end of each calendar year, separate electric and natural gas earnings calculations are made for the calendar year just ended. These earnings tests reflect actual decoupled revenues, normalized power supply costs and other normalizing adjustments. If the Company earns more than its authorized ROR in Washington, 50 percent of excess earnings are rebated to customers through adjustments to decoupling surcharge or rebate balances. See below for a summary of cumulative balances under the decoupling and earnings sharing mechanisms. The Company has proposed to modify this earnings test in its 2022 general rate case, so that if the Company earns more than 0.5 percent higher than the ROR authorized by the WUTC in the multi-year rate plan, the Company would defer these excess revenues and later return them to customers. Idaho FCA and Earnings Sharing Mechanisms In Idaho, the IPUC approved the implementation of FCAs for electric and natural gas through March 31, 2025. Oregon Decoupling Mechanism In Oregon, the Company has a decoupling mechanism for natural gas. An earnings review is conducted on an annual basis. In the annual earnings review, if the Company earns more than 100 basis points above its allowed ROE, one-third of the earnings above the 100 basis points would be deferred and later returned to customers. The earnings review is separate from the decoupling mechanism and was in place prior to decoupling. Cumulative Decoupling and Earnings Sharing Mechanism Balances As of December 31, 2021 and December 31, 2020, the Company had the following cumulative balances outstanding related to decoupling and earnings sharing mechanisms in its various jurisdictions (dollars in thousands): December 31, December 31, 2021 2020 Washington Decoupling surcharge $ 13,522 $ 21,340 Idaho Decoupling (rebate) surcharge $ ( 1,450 ) $ 1,202 Provision for earnings sharing rebate ( 686 ) ( 686 ) Oregon Decoupling surcharge (rebate) $ 3,152 $ ( 1,262 ) There were no earnings sharing rebates associated with Washington and Oregon as of December 31, 2021 and December 31, 2020 .

Information by Business Segment

Information by Business Segments	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Information by Business Segments	NOTE 24. INFORMATION BY BUSINESS SEGMENTS The business segment presentation reflects the basis used by the Company's management to analyze performance and determine the allocation of resources. The Company's management evaluates performance based on income (loss) from operations before income taxes as well as net income (loss) 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 Alaska Total Utility Other Intersegment Total For the year ended Operating revenues $ 1,392,999 $ 45,366 $ 1,438,365 $ 571 $ — $ 1,438,936 Resource costs 493,289 3,834 497,123 — — 497,123 Other operating expenses 352,241 13,884 366,125 5,927 — 372,052 Depreciation and amortization 221,552 10,363 231,915 261 — 232,176 Income (loss) from operations 217,663 16,186 233,849 ( 5,617 ) — 228,232 Interest expense (2) 99,629 6,096 105,725 522 ( 95 ) 106,152 Income taxes 6,029 2,763 8,792 3,239 — 12,031 Net income from continuing 125,558 7,224 132,782 14,552 — 147,334 Capital expenditures (3) 435,887 4,052 439,939 1,270 — 441,209 For the year ended Operating revenues $ 1,277,468 $ 42,809 $ 1,320,277 $ 1,614 $ — $ 1,321,891 Resource costs 396,543 1,966 398,509 — — 398,509 Other operating expenses 341,709 12,905 354,614 5,344 — 359,958 Depreciation and amortization 213,701 9,806 223,507 716 — 224,223 Income (loss) from operations 220,058 17,088 237,146 ( 4,446 ) — 232,700 Interest expense (2) 98,451 6,272 104,723 524 ( 186 ) 105,061 Income taxes 4,921 3,011 7,932 ( 881 ) — 7,051 Net income (loss) from 124,810 8,095 132,905 ( 3,417 ) — 129,488 Capital expenditures (3) 397,292 7,014 404,306 1,368 — 405,674 For the year ended Operating revenues $ 1,295,873 $ 37,265 $ 1,333,138 $ 12,484 $ — $ 1,345,622 Resource costs 442,471 ( 2,654 ) 439,817 — — 439,817 Other operating expenses (4) 352,170 12,717 364,887 18,883 — 383,770 Depreciation and amortization 195,697 9,668 205,365 629 — 205,994 Income (loss) from operations 200,994 16,423 217,417 ( 7,028 ) — 210,389 Interest expense (2) 97,866 6,385 104,251 1,032 ( 929 ) 104,354 Income taxes 28,363 2,816 31,179 195 — 31,374 Net income from continuing 183,977 7,458 191,435 5,544 — 196,979 Capital expenditures (3) 434,077 8,433 442,510 835 — 443,345 Total Assets: As of December 31, 2021 $ 6,458,244 $ 265,422 $ 6,723,666 $ 132,158 $ ( 2,241 ) $ 6,853,583 As of December 31, 2020 $ 6,035,340 $ 268,971 $ 6,304,311 $ 109,658 $ ( 11,872 ) $ 6,402,097 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. Intersegment eliminations reported as assets represent intersegment accounts receivable. (2) Including interest expense to affiliated trusts. (3) The capital expenditures for the other businesses are included in other investing activities on the Consolidated Statements of Cash Flows. (4) Other operating expenses for Avista Utilities for 2019 include merger transaction costs which are separately disclosed on the Consolidated Statements of Income.

Termination of Proposed Acquisi

Termination of Proposed Acquisition by Hydro One	12 Months Ended
	Dec. 31, 2021
Business Combinations [Abstract]
Termination of Proposed Acquisition by Hydro One	NOTE 25. TERMINATION OF PROP OSED ACQUISITION BY HYDRO ONE In July 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. Termination of the Merger Agreement Due to the denial of the proposed merger by certain of the Company's regulatory commissions, in January 2019, Avista Corp., Hydro One and certain subsidiaries thereof, entered into a Termination Agreement indicating their mutual agreement to terminate the Merger Agreement. Pursuant to the terms of the Termination Agreement, Hydro One paid Avista Corp. a $ 103 million termination fee in January 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 were $ 19.7 million pre-tax and included financial advisers' fees, legal fees, consulting fees and employee time.

Sale of METALfx

Sale of METALfx	12 Months Ended
	Dec. 31, 2021
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Sale of METALfx	NOTE 26. SAL E 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 in April 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). The sales transaction provided cash proceeds to Avista Corp., net of payments to the minority holder, contractually obligated compensation payments and other transaction expenses, of $ 16.5 million and resulted in a net gain after-tax of $ 3.3 million. 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 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 24. 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 Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
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 24 for business segment information. See Note 26 for discussion of the sale of METALfx, which was an unregulated subsidiary of the Company.
Basis of Reporting	Basis of Reporting The consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants (see Note 8).
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported for assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates include: • determining the market value of energy commodity derivative assets and liabilities, • pension and other postretirement benefit plan obligations, • contingent liabilities, • goodwill impairment testing, • recoverability of regulatory assets, and • unbilled revenues. Changes in these estimates and assumptions are considered reasonably possible and may have a material effect on the consolidated financial statements and thus actual results could differ from the amounts reported and disclosed herein.
Regulation	Regulation The Company is subject to state regulation in Washington, Idaho, Montana, Oregon and Alaska. The Company is also subject to federal regulation primarily by the FERC, as well as various other federal agencies with regulatory oversight of particular aspects of its operations. Regulatory Deferred Charges and Credits The Company prepares its consolidated financial statements in accordance with regulatory accounting practices because: • rates for regulated services are established by or subject to approval by independent third-party regulators, • the regulated rates are designed to recover the cost of providing the regulated services, and • in view of demand for the regulated services and the level of competition, it is reasonable to assume that rates can be charged to and collected from customers at levels that will recover costs. Regulatory accounting practices require that certain costs and/or obligations (such as incurred power and natural gas costs not currently reflected in rates, but expected to be recovered or refunded in the future), are reflected as deferred charges or credits on the Consolidated Balance Sheets. These costs and/or obligations are not reflected in the Consolidated Statements of Income until the period during which matching revenues are recognized. The Company also has decoupling revenue deferrals. See Note 4 for discussion on decoupling revenue deferrals. If at some point in the future the Company determines that it no longer meets the criteria for continued application of regulatory accounting practices for all or a portion of its regulated operations, the Company could be: • required to write off its regulatory assets, and • precluded from the future deferral of costs or decoupled revenues not recovered through rates at the time such amounts are incurred, even if the Company expected to recover these amounts from customers in the future. See Note 23 for further details of regulatory assets and liabilities.
Depreciation	Depreciation For utility operations, depreciation expense is estimated by a method of depreciation accounting utilizing composite rates for utility plant. Such rates are designed to provide for retirements of properties at the expiration of their service lives. For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31: 2021 2020 2019 Avista Utilities Ratio of depreciation to average depreciable property 3.54 % 3.43 % 3.28 % Alaska Electric Light and Power Company Ratio of depreciation to average depreciable property 2.77 % 2.77 % 2.48 % The average service lives for the following broad categories of utility plant in service are (in years): Avista Utilities Alaska Electric Light Electric thermal/other production 26 42 Hydroelectric production 81 42 Electric transmission 50 43 Electric distribution 39 40 Natural gas distribution property 44 N/A Other shorter-lived general plant 8 18
Allowance for Funds Used During Construction	Allowance for Funds Used During Construction AFUDC represents the cost of both the debt and equity funds used to finance utility plant additions during the construction period. As prescribed by regulatory authorities, AFUDC is capitalized as a part of the cost of utility plant. The debt component of AFUDC is credited against total interest expense in the Consolidated Statements of Income in the line item “capitalized interest.” The equity component of AFUDC is included in the Consolidated Statements of Income in the line item “other income-net.” The Company is permitted, under established regulatory rate practices, to recover the capitalized AFUDC, and a reasonable return thereon, through its inclusion in rate base and the provision for depreciation after the related utility plant is placed in service. Cash inflow related to AFUDC does not occur until the related utility plant is placed in service and included in rate base. The WUTC and IPUC have authorized Avista Utilities to calculate AFUDC using its allowed rate of return. To the extent amounts calculated using this rate exceed the AFUDC amounts calculated using the FERC formula, Avista Utilities capitalizes the excess as a regulatory asset. The regulatory asset associated with plant in service is amortized over the average useful life of Avista Utilities' utility plant which is approximately 30 years. The regulatory asset associated with construction work in progress is not amortized until the plant is placed in service. The effective AFUDC rate was the following for the years ended December 31: 2021 2020 2019 Avista Utilities 7.19 % 7.25 % 7.39 % Alaska Electric Light and Power Company 8.90 % 8.04 % 8.96 %
Income Taxes	Income Taxes Deferred income tax assets represent future income tax deductions the Company expects to utilize in future tax returns to reduce taxable income. Deferred income tax liabilities represent future taxable income the Company expects to recognize in future tax returns. Deferred tax assets and liabilities arise when there are temporary differences resulting from differing treatment of items for tax and accounting purposes. A deferred income tax asset or liability is determined based on the enacted tax rates that will be in effect when the temporary differences between the financial statement carrying amounts and tax basis of existing assets and liabilities are expected to be reported in the Company’s consolidated income tax returns. The effect on deferred income taxes from a change in tax rates is recognized in income in the period that includes the enactment date unless a regulatory order specifies deferral of the effect of the change in tax rates over a longer period of time. The Company establishes a valuation allowance when it is more likely than not that all, or a portion, of a deferred tax asset will not be realized. Deferred income tax assets and liabilities and regulatory assets and liabilities are established for income tax benefits flowed through to customers. The Company's largest deferred income tax item is the difference between the book and tax basis of utility plant. This item results from the temporary difference on depreciation expense. In early tax years, this item is recorded as a deferred income tax liability that will eventually reverse and become subject to income tax in later tax years. The Company did no t incur any penalties on income tax positions in 2021, 2020 or 2019. The Company would recognize interest accrued related to income tax positions as interest expense and any penalties incurred as other operating expense.
Stock-Based Compensation	Stock-Based Compensation The Company currently issues three types of stock-based compensation awards - restricted shares, market-based awards and performance-based awards. Historically, these stock compensation awards have not been material to the Company's overall financial results. Compensation cost relating to share-based payment transactions is recognized in the Company’s financial statements based on the fair value of the equity instruments issued and recorded over the requisite service period. The Company recorded stock-based compensation expense (included in other operating expenses) and income tax benefits in the Consolidated Statements of Income of the following amounts for the years ended December 31 (dollars in thousands): 2021 2020 2019 Stock-based compensation expense $ 4,713 $ 5,846 $ 11,353 Income tax benefits 990 1,228 2,384 Excess tax expenses on settled share-based employee ( 909 ) ( 165 ) ( 612 ) Restricted share awards vest in equal thirds each year over 3 years and are payable in Avista Corp. common stock at the end of each year if the service condition is met. Restricted stock is valued at the close of market of the Company’s common stock on the grant date. Total Shareholder Return (TSR) awards are market-based awards and Cumulative Earnings Per Share (CEPS) awards are performance awards. Both types of awards vest after a period of 3 years and are payable in cash or Avista Corp. common stock at the end of the three-year period. The method of settlement is at the discretion of the Company and historically the Company has settled these awards through issuance of Avista Corp. common stock and intends to continue this practice. Both types of awards entitle the recipients to dividend equivalent rights, are subject to forfeiture under certain circumstances, and are subject to meeting specific market or performance conditions. Based on the level of attainment of the market or performance conditions, the amount of cash paid or common stock issued will range from 0 to 200 percent of the initial awards granted. Dividend equivalent rights are accumulated and paid out only on shares that eventually vest and have met the market and performance conditions. The Company accounts for both the TSR awards and CEPS awards as equity awards and compensation cost for these awards is recognized over the requisite service period, provided that the requisite service period is rendered. For TSR awards, if the market condition is not met at the end of the three-year service period, there will be no change in the cumulative amount of compensation cost recognized, since the awards are still considered vested even though the market metric was not met. For CEPS awards, at the end of the three-year service period, if the internal performance metric of cumulative earnings per share is not met, all compensation cost for these awards is reversed as these awards are not considered vested. The fair value of each TSR award is estimated on the date of grant using a statistical model that incorporates the probability of meeting the market targets based on historical returns relative to a peer group. The estimated fair value of the CEPS awards was estimated on the date of grant as the share price of Avista Corp. common stock on the date of grant. The following table summarizes the number of grants, vested and unvested shares, earned shares (based on market metrics), and other pertinent information related to the Company's stock compensation awards for the years ended December 31: 2021 2020 2019 Restricted Shares Shares granted during the year 62,594 45,540 50,061 Shares vested during the year 34,854 56,203 48,228 Unvested shares at end of year 96,127 71,706 93,351 Unrecognized compensation expense at end of year $ 2,215 $ 2,003 $ 2,054 TSR Awards TSR shares granted during the year 64,910 47,848 99,214 TSR shares vested during the year 77,174 71,299 106,858 TSR shares earned based on market metrics 58,652 — — Unvested TSR shares at end of year 107,854 122,133 178,035 Unrecognized compensation expense at end of year $ 2,653 $ 2,296 $ 3,377 CEPS Awards CEPS shares granted during the year 64,910 47,848 49,609 CEPS shares vested during the year 38,590 35,622 53,454 CEPS shares earned based on market metrics 26,627 63,763 106,908 Unvested CEPS shares at end of year 107,854 83,464 88,990 Unrecognized compensation expense at end of year $ 1,223 $ 1,090 $ 2,401 Outstanding restricted, TSR and CEPS share awards include a dividend component that is paid in cash. A liability for the dividends payable related to these awards is accrued as dividends are announced throughout the life of the award. As of December 31, 2021 and 2020, the Company had recognized a liability of $ 1.5 million an d $ 0.8 million, respectively, related to the dividend equivalents payable on the outstanding and unvested share grants.
Other Expense (Income) - Net	Other Income - Net Other income - net consisted of the following items for the years ended December 31 (dollars in thousands): 2021 2020 2019 Interest income $ ( 1,943 ) $ ( 1,952 ) $ ( 2,587 ) Interest on regulatory deferrals ( 1,206 ) ( 1,222 ) ( 1,460 ) Equity-related AFUDC ( 7,004 ) ( 6,970 ) ( 6,585 ) Non-service portion of pension and other postretirement benefit 1,386 6,433 8,899 Earnings on investments ( 21,402 ) ( 905 ) ( 14,299 ) Other expense (income) ( 3,129 ) ( 201 ) 1,104 Total $ ( 33,298 ) $ ( 4,817 ) $ ( 14,928 )
Earnings per Common Share Attributable to Avista Corporation Shareholders	Earnings per Common Share Attributable to Avista Corporation Shareholders Basic earnings per common share attributable to Avista Corp. shareholders is computed by dividing net income attributable to Avista Corp. shareholders by the weighted-average number of common shares outstanding for the period. Diluted earnings per common share attributable to Avista Corp. shareholders is calculated by dividing net income attributable to Avista Corp. shareholders by diluted weighted-average common shares outstanding during the period, including common stock equivalent shares outstanding using the treasury stock method, unless such shares are anti-dilutive. Common stock equivalent shares include shares issuable under contingent stock awards. See Note 21 for earnings per common share calculations.
Cash and Cash Equivalents	Cash and Cash Equivalents For the purposes of the Consolidated Statements of Cash Flows, the Company considers all temporary investments with a maturity of three months or less when purchased to be cash equivalents.
Allowance For Doubtful Accounts	Allowance for Doubtful Accounts The Company maintains an allowance for doubtful accounts to provide for estimated and potential losses on accounts receivable. The Company determines the allowance for utility and other customer accounts receivable based on historical write-offs as compared to accounts receivable and operating revenues. Additionally, the Company establishes specific allowances for certain individual accounts. The following table presents the activity in the allowance for doubtful accounts during the years ended December 31 (dollars in thousands): 2021 2020 2019 Allowance as of the beginning of the year $ 11,387 $ 2,419 $ 5,233 Additions expensed during the year (1) 9,279 11,280 460 Net deductions (2) ( 10,201 ) ( 2,312 ) ( 3,274 ) Allowance as of the end of the year $ 10,465 $ 11,387 $ 2,419 (1) Increases in 2021 and 2020 related to COVID-19 bad debt expense in excess of the amount recovered through rates. (2) Increase in 2021 relates to COVID forgiveness program.
Utility Plant in Service	Utility Plant in Service The cost of additions to utility plant in service, including an allowance for funds used during construction and replacements of units of property and improvements, is capitalized. The cost of depreciable units of property retired plus the cost of removal less salvage is charged to accumulated depreciation.
Asset Retirement Obligations	Asset Retirement Obligations The Company records the fair value of a liability for an ARO in the period in which it is incurred. When the liability is initially recorded, the associated costs of the ARO are capitalized as part of the carrying amount of the related long-lived asset. The liability is accreted to its present value each period and the related capitalized costs are depreciated over the useful life of the related asset. In addition, if there are changes in the estimated timing or estimated costs of the AROs, adjustments are recorded during the period new information becomes available as an increase or decrease to the liability, with the offset recorded to the related long-lived asset. Upon retirement of the asset, the Company either settles the ARO for its recorded amount or recognizes a regulatory asset or liability for the difference, which will be surcharged/refunded to customers through the ratemaking process. The Company records regulatory assets and liabilities for the difference between asset retirement costs currently recovered in rates and AROs recorded since asset retirement costs are recovered through rates charged to customers (see Note 10 for further discussion of the Company's AROs). The Company recovers certain asset retirement costs through rates charged to customers as a portion of its depreciation expense for which the Company has not recorded asset retirement obligations. The Company has recorded the amount of estimated retirement costs collected from customers (that do not represent legal or contractual obligations) and included them as a non-current regulatory liability on the Consolidated Balance Sheets in the following amounts as of December 31 (dollars in thousands): 2021 2020 Regulatory liability for utility plant retirement costs $ 350,190 $ 325,832
Goodwill	Goodwill Goodwill arising from acquisitions represents the future economic benefit arising from other assets acquired in a business combination that are not individually identified and separately recognized. The Company evaluates goodwill for impairment using a fair value to carrying amount comparison (Step 1). The Company completed its annual evaluation of goodwill for potential impairment as of November 30, 2021 and determined that goodwill was not impaired at that time (carrying value was less than the determined fair value). There were no events or circumstances that changed between November 30, 2021 and December 31, 2021 that would more likely than not reduce the fair values of the reporting units below their carrying amounts. There were no changes in the carrying amount of goodwill during 2020 and 2021, and the balance was as follows (dollars in thousands): AEL&P Accumulated Impairment Losses Total Balance as of December 31, 2020 and 2021 $ 52,426 $ - $ 52,426
Derivative Assets and Liabilities	Derivative Assets and Liabilities Derivatives are recorded as either assets or liabilities on the Consolidated Balance Sheets measured at estimated fair value. The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and costs result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rates 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 regulatory asset or liability is amortized as a component of interest expense over the term of the associated debt. The Company records an offset of interest rate swap derivative assets and liabilities with regulatory assets and liabilities, based on the prior practice of the commissions to provide recovery through the ratemaking process. 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 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 swap derivatives and foreign currency exchange derivatives, are reported at estimated fair value on the Consolidated Balance Sheets. See Note 18 for the Company’s fair value disclosures.
Unamortized Debt Expense	Unamortized Debt Expense Unamortized debt expense includes debt issuance costs that are amortized over the life of the related debt. These costs are recorded as an offset to Long-Term Debt on the Consolidated Balance Sheets. Unamortized Debt Repurchase Costs Premiums paid or discounts received to repurchase debt are amortized over the remaining life of the original debt that was repurchased or, if new debt is issued in connection with the repurchase, these costs are amortized over the life of the new debt. These costs are recovered through retail rates as a component of interest expense.
Appropriated Retained Earnings	Appropriated Retained Earnings In accordance with the hydroelectric licensing requirements of section 10(d) of the Federal Power Act (FPA), the Company maintains an appropriated retained earnings account for any earnings in excess of the specified rate of return on the Company's investment in the licenses for its various hydroelectric projects. Per section 10(d) of the FPA, the Company must maintain these excess earnings in an appropriated retained earnings account until the termination of the licensing agreements or apply them to reduce the net investment in the licenses of the hydroelectric projects at the discretion of the FERC. The Company calculates the earnings in excess of the specified rate of return on an annual basis, usually during the second quarter. The appropriated retained earnings amounts included in retained earnings were as follows as of December 31 (dollars in thousands): 2021 2020 Appropriated retained earnings $ 53,620 $ 47,473
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. As of December 31, 2021 , the Company has not recorded any significant amounts related to unresolved contingencies. See Note 22 for further discussion of the Company's commitments and contingencies.
Inventory	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 regulated operations and the lower of cost or market for non-regulated operations and consisted of the following as of December 31 (dollars in thousands): 2021 2020 Materials and supplies $ 62,003 $ 53,258 Fuel stock 5,126 4,658 Stored natural gas 17,604 9,535 Total $ 84,733 $ 67,451

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Ratio of Depreciation to Average Depreciable Property and Average Service Lives for Utility Plan in Service	For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31: 2021 2020 2019 Avista Utilities Ratio of depreciation to average depreciable property 3.54 % 3.43 % 3.28 % Alaska Electric Light and Power Company Ratio of depreciation to average depreciable property 2.77 % 2.77 % 2.48 % The average service lives for the following broad categories of utility plant in service are (in years): Avista Utilities Alaska Electric Light Electric thermal/other production 26 42 Hydroelectric production 81 42 Electric transmission 50 43 Electric distribution 39 40 Natural gas distribution property 44 N/A Other shorter-lived general plant 8 18 The gross balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in thousands): 2021 2020 Avista Utilities: Electric production $ 1,494,371 $ 1,457,497 Electric transmission 945,624 862,987 Electric distribution 2,093,937 1,978,868 Electric construction work-in-progress (CWIP) and other 424,733 384,372 Electric total 4,958,665 4,683,724 Natural gas underground storage 55,684 53,351 Natural gas distribution 1,356,477 1,282,563 Natural gas CWIP and other 87,852 83,644 Natural gas total 1,500,013 1,419,558 Common plant (including CWIP) 740,339 712,609 Total Avista Utilities 7,199,017 6,815,891 AEL&P: Electric production 106,094 105,076 Electric transmission 22,691 22,419 Electric distribution 27,138 25,814 Electric CWIP and other 7,319 6,677 Electric total 163,242 159,986 Common plant 9,726 9,687 Total AEL&P 172,968 169,673 Total gross utility property 7,371,985 6,985,564 Other (1) 17,818 16,394 Total $ 7,389,803 $ 7,001,958 (1) Included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets. Accumulated depreciation was $ 2.3 million as of December 31, 2021 and $ 2.2 million as of December 31, 2020 for the other businesses.
Summary of Effective AFUDC Rate	The effective AFUDC rate was the following for the years ended December 31: 2021 2020 2019 Avista Utilities 7.19 % 7.25 % 7.39 % Alaska Electric Light and Power Company 8.90 % 8.04 % 8.96 %
Stock-Based Compensation	The Company recorded stock-based compensation expense (included in other operating expenses) and income tax benefits in the Consolidated Statements of Income of the following amounts for the years ended December 31 (dollars in thousands): 2021 2020 2019 Stock-based compensation expense $ 4,713 $ 5,846 $ 11,353 Income tax benefits 990 1,228 2,384 Excess tax expenses on settled share-based employee ( 909 ) ( 165 ) ( 612 ) The following table summarizes the number of grants, vested and unvested shares, earned shares (based on market metrics), and other pertinent information related to the Company's stock compensation awards for the years ended December 31: 2021 2020 2019 Restricted Shares Shares granted during the year 62,594 45,540 50,061 Shares vested during the year 34,854 56,203 48,228 Unvested shares at end of year 96,127 71,706 93,351 Unrecognized compensation expense at end of year $ 2,215 $ 2,003 $ 2,054 TSR Awards TSR shares granted during the year 64,910 47,848 99,214 TSR shares vested during the year 77,174 71,299 106,858 TSR shares earned based on market metrics 58,652 — — Unvested TSR shares at end of year 107,854 122,133 178,035 Unrecognized compensation expense at end of year $ 2,653 $ 2,296 $ 3,377 CEPS Awards CEPS shares granted during the year 64,910 47,848 49,609 CEPS shares vested during the year 38,590 35,622 53,454 CEPS shares earned based on market metrics 26,627 63,763 106,908 Unvested CEPS shares at end of year 107,854 83,464 88,990 Unrecognized compensation expense at end of year $ 1,223 $ 1,090 $ 2,401
Other Expense (Income) - Net	Other income - net consisted of the following items for the years ended December 31 (dollars in thousands): 2021 2020 2019 Interest income $ ( 1,943 ) $ ( 1,952 ) $ ( 2,587 ) Interest on regulatory deferrals ( 1,206 ) ( 1,222 ) ( 1,460 ) Equity-related AFUDC ( 7,004 ) ( 6,970 ) ( 6,585 ) Non-service portion of pension and other postretirement benefit 1,386 6,433 8,899 Earnings on investments ( 21,402 ) ( 905 ) ( 14,299 ) Other expense (income) ( 3,129 ) ( 201 ) 1,104 Total $ ( 33,298 ) $ ( 4,817 ) $ ( 14,928 )
Allowance for Doubtful Accounts	The following table presents the activity in the allowance for doubtful accounts during the years ended December 31 (dollars in thousands): 2021 2020 2019 Allowance as of the beginning of the year $ 11,387 $ 2,419 $ 5,233 Additions expensed during the year (1) 9,279 11,280 460 Net deductions (2) ( 10,201 ) ( 2,312 ) ( 3,274 ) Allowance as of the end of the year $ 10,465 $ 11,387 $ 2,419 (1) Increases in 2021 and 2020 related to COVID-19 bad debt expense in excess of the amount recovered through rates. (2) Increase in 2021 relates to COVID forgiveness program.
Estimated Retirement Costs Collected from Customers	The Company has recorded the amount of estimated retirement costs collected from customers (that do not represent legal or contractual obligations) and included them as a non-current regulatory liability on the Consolidated Balance Sheets in the following amounts as of December 31 (dollars in thousands): 2021 2020 Regulatory liability for utility plant retirement costs $ 350,190 $ 325,832
Summary of Changes in Carrying Amount of Goodwill	There were no changes in the carrying amount of goodwill during 2020 and 2021, and the balance was as follows (dollars in thousands): AEL&P Accumulated Impairment Losses Total Balance as of December 31, 2020 and 2021 $ 52,426 $ - $ 52,426
Summary of Appropriated Retained Earnings Amount Included in Retained Earnings	The appropriated retained earnings amounts included in retained earnings were as follows as of December 31 (dollars in thousands): 2021 2020 Appropriated retained earnings $ 53,620 $ 47,473

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
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 regulated operations and the lower of cost or market for non-regulated operations and consisted of the following as of December 31 (dollars in thousands): 2021 2020 Materials and supplies $ 62,003 $ 53,258 Fuel stock 5,126 4,658 Stored natural gas 17,604 9,535 Total $ 84,733 $ 67,451
Schedule of Other Current Assets	Other current assets consisted of the following as of December 31 (dollars in thousands): 2021 2020 Collateral posted for derivative instruments after netting with outstanding $ 21,477 $ 4,336 Prepayments 24,387 24,411 Income taxes receivable 29,615 49,814 Other 5,275 6,324 Total $ 80,754 $ 84,885
Other Property and Investments-Net and Other Non-Current Assets	Other property and investments-net and other non-current assets consisted of the following as of December 31 (dollars in thousands): 2021 2020 Operating lease ROU assets $ 70,133 $ 71,891 Finance lease ROU assets 43,697 47,338 Non-utility property 20,033 19,508 Equity investments 91,057 59,318 Investment in affiliated trust 11,547 11,547 Notes receivable 14,949 14,454 Deferred compensation assets 9,513 9,174 Assets held for sale (1) — 3,462 Other 19,614 26,947 Total $ 280,543 $ 263,639 (1) The Company sold certain subsidiary assets associated with Steam Plant Square and Brew Pub during 2021.
Other Current Liabilities	Other current liabilities consisted of the following as of December 31 (dollars in thousands): 2021 2020 Accrued taxes other than income taxes $ 41,706 $ 45,099 Derivative liabilities 28,801 14,008 Employee paid time off accruals 27,741 26,495 Accrued interest 17,538 17,083 Pensions and other postretirement benefits 13,582 11,987 Other 39,493 35,159 Total $ 168,861 $ 149,831
Schedule of Other Non-Current Liabilities and Deferred Credits	Other non-current liabilities and deferred credits consisted of the following as of December 31 (dollars in thousands): 2021 2020 Operating lease liabilities $ 66,068 $ 67,716 Finance lease liabilities 45,730 48,815 Deferred investment tax credits 29,313 29,866 Asset retirement obligations 17,142 17,194 Derivative liabilities 4,525 37,427 Other 15,347 13,981 Total $ 178,125 $ 214,999

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Unbilled Accounts Receivable	Accounts receivable includes unbilled energy revenues of the following amounts as of December 31 (dollars in thousands): 2021 2020 Unbilled accounts receivable $ 74,479 $ 71,258
Schedule of Utilities Operating Revenue Expense Taxes	Utility-related taxes that were included in revenue from contracts with customers were as follows for the years ended December 31 (dollars in thousands): 2021 2020 2019 Utility-related taxes $ 62,736 $ 59,319 $ 59,528
Disaggregation of Revenue	Disaggregation of Total Operating Revenue The following table disaggregates total operating revenue by segment and source for the years ended December 31 (dollars in thousands): 2021 2020 2019 Avista Utilities Revenue from contracts with customers $ 1,233,904 $ 1,157,746 $ 1,152,125 Derivative revenues 152,590 110,313 118,741 Alternative revenue programs ( 6,635 ) ( 3,814 ) 9,614 Deferrals and amortizations for rate refunds to customers 2,984 5,335 4,509 Other utility revenues 10,156 7,888 10,884 Total Avista Utilities 1,392,999 1,277,468 1,295,873 AEL&P Revenue from contracts with customers 45,051 42,624 36,779 Deferrals and amortizations for rate refunds to customers ( 190 ) ( 190 ) ( 190 ) Other utility revenues 505 375 676 Total AEL&P 45,366 42,809 37,265 Other Revenue from contracts with customers 2 564 11,286 Other revenues 569 1,050 1,198 Total Other 571 1,614 12,484 Total operating revenues $ 1,438,936 $ 1,321,891 $ 1,345,622 Utility Revenue from Contracts with Customers by Type and Service The following table disaggregates revenue from contracts with customers associated with the Company's electric operations for the years ended December 31 (dollars in thousands): 2021 2020 2019 Avista Utilities AEL&P Total Utility Avista Utilities AEL&P Total Utility Avista Utilities AEL&P Total Utility ELECTRIC OPERATIONS Revenue from Residential $ 394,717 $ 18,940 $ 413,657 $ 377,785 $ 18,618 $ 396,403 $ 369,102 $ 17,134 $ 386,236 Commercial and 326,173 25,861 352,034 303,972 23,754 327,726 317,589 19,391 336,980 Industrial 106,756 — 106,756 103,103 — 103,103 105,802 — 105,802 Public street and 7,472 250 7,722 7,303 252 7,555 7,448 254 7,702 Total retail 835,118 45,051 880,169 792,163 42,624 834,787 799,941 36,779 836,720 Transmission 21,005 — 21,005 18,236 — 18,236 18,180 — 18,180 Other revenue from 33,870 — 33,870 19,252 — 19,252 26,969 — 26,969 Total revenue $ 889,993 $ 45,051 $ 935,044 $ 829,651 $ 42,624 $ 872,275 $ 845,090 $ 36,779 $ 881,869 The following table disaggregates revenue from contracts with customers associated with the Company's natural gas operations for the years ended December 31 (dollars in thousands): 2021 2020 2019 Avista Utilities Avista Utilities Avista Utilities NATURAL GAS OPERATIONS Revenue from contracts with customers Residential $ 221,405 $ 213,612 $ 196,430 Commercial 100,819 94,937 92,168 Industrial and interruptible 7,796 7,128 5,263 Total retail revenue 330,020 315,677 293,861 Transportation 8,547 7,917 8,674 Other revenue from contracts with customers 5,344 4,501 4,500 Total revenue from contracts with customers $ 343,911 $ 328,095 $ 307,035

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Components of Lease Expense	The components of lease expense were as follows for the year ended December 31 (dollars in thousands): 2021 2020 Operating lease cost: Fixed lease cost (Other operating expenses) $ 4,970 $ 4,746 Variable lease cost (Other operating expenses) 1,180 1,099 Total operating lease cost $ 6,150 $ 5,845 Finance lease cost: Amortization of ROU asset (Depreciation and amortization) $ 3,641 $ 3,641 Interest on lease liabilities (Interest expense) 2,522 2,662 Total finance lease cost $ 6,163 $ 6,303
Summary of Supplemental Cash Flow Information related to Leases	Supplemental cash flow information related to leases was as follows for the year ended December 31 (dollars in thousands): 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflows: Operating lease payments $ 4,805 $ 4,612 Interest on finance lease 2,522 2,662 Total operating cash outflows $ 7,327 $ 7,274 Finance cash outflows: Principal payments on finance lease $ 2,935 $ 2,800
Summary of Supplemental Balance Sheet Information Related to Leases	Supplemental balance sheet information related to leases was as follows for December 31 (dollars in thousands): December 31, December 31, 2021 2020 Operating Leases Operating lease ROU assets (Other property and investments-net $ 70,133 $ 71,891 Other current liabilities $ 4,301 $ 4,249 Other non-current liabilities and deferred credits 66,068 67,716 Total operating lease liabilities $ 70,369 $ 71,965 Finance Leases Finance lease ROU assets (Other property and investments-net $ 43,697 $ 47,338 Other current liabilities $ 3,085 $ 2,935 Other non-current liabilities and deferred credits 45,730 48,815 Total finance lease liabilities $ 48,815 $ 51,750 Weighted Average Remaining Lease Term Operating leases 24.22 years 25.20 years Finance leases 6.32 years 7.22 years Weighted Average Discount Rate Operating leases 4.28 % 4.28 % Finance leases 4.35 % 4.62 %
Summary of Maturities of Lease Liabilities	Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2021 (dollars in thousands): Operating Leases Finance Leases 2022 $ 4,820 $ 5,460 2023 4,849 5,456 2024 4,875 5,459 2025 4,882 5,454 2026 4,867 5,456 Thereafter 91,845 38,204 Total lease payments $ 116,138 $ 65,489 Less: imputed interest ( 45,769 ) ( 16,674 ) Total $ 70,369 $ 48,815 Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2020 (dollars in thousands): Operating Leases Finance Leases 2021 $ 4,779 $ 5,457 2022 4,799 5,460 2023 4,827 5,456 2024 4,852 5,459 2025 4,865 5,454 Thereafter 96,734 43,661 Total lease payments $ 120,856 $ 70,947 Less: imputed interest ( 48,891 ) ( 19,197 ) Total $ 71,965 $ 51,750
Summary of Maturities of Lease Liabilities	Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2021 (dollars in thousands): Operating Leases Finance Leases 2022 $ 4,820 $ 5,460 2023 4,849 5,456 2024 4,875 5,459 2025 4,882 5,454 2026 4,867 5,456 Thereafter 91,845 38,204 Total lease payments $ 116,138 $ 65,489 Less: imputed interest ( 45,769 ) ( 16,674 ) Total $ 70,369 $ 48,815 Maturities of lease liabilities (including principal and interest) were as follows as of December 31, 2020 (dollars in thousands): Operating Leases Finance Leases 2021 $ 4,779 $ 5,457 2022 4,799 5,460 2023 4,827 5,456 2024 4,852 5,459 2025 4,865 5,454 Thereafter 96,734 43,661 Total lease payments $ 120,856 $ 70,947 Less: imputed interest ( 48,891 ) ( 19,197 ) Total $ 71,965 $ 51,750

Derivatives and Risk Manageme_2

Derivatives and Risk Management (Tables)	12 Months Ended
	Dec. 31, 2021
Derivative Instruments and Hedges, Assets [Abstract]
Schedule of Energy Commodity Derivative Volumes	The following table presents the underlying energy commodity derivative volumes as of December 31, 2021 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) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) 2022 129 — 7,114 61,405 234 452 3,933 31,485 2023 — — 378 23,218 — — 1,360 9,323 2024 — — 228 3,413 — — 1,370 228 2025 — — — — — — 1,115 — As of December 31, 2021 , there are no expected deliveries of energy commodity derivatives afte r 2 0 25. The following table presents the underlying energy commodity derivative volumes as of December 31, 2020 that were expected to be delivered in each respective year (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) 2021 1 224 10,353 65,188 17 451 5,448 39,273 2022 — — 450 25,525 — — 1,360 12,030 2023 — — — 4,950 — — 1,360 900 2024 — — — — — — 1,370 — 2025 — — — — — — 1,115 — As of December 31, 2020 , there were no expected deliveries of energy commodity derivatives after 2 0 25. (1) Physical transactions represent commodity transactions in which Avista Corp. will take or make delivery of either electricity or natural gas; financial transactions represent derivative instruments with delivery of cash in the amount of the benefit or cost but with no physical delivery of the commodity, such as futures, swap derivatives, options, or forward contracts.
Summary of Foreign Currency Exchange Derivatives	The following table summarizes the foreign currency exchange derivatives that Avista Corp. has outstanding as of December 31 (dollars in thousands): 2021 2020 Number of contracts 25 22 Notional amount (in United States dollars) $ 8,571 $ 3,860 Notional amount (in Canadian dollars) 10,957 4,949
Summary of Unsettled Interest Rate Swap Derivatives	The following table summarizes the unsettled interest rate swap derivatives that Avista Corp. has outstanding as of the balance sheet date indicated below (dollars in thousands): Balance Sheet Date Number of Contracts Notional Amount Mandatory Cash December 31, 2021 13 140,000 2022 2 20,000 2023 1 10,000 2024 December 31, 2020 4 45,000 2021 11 120,000 2022 1 10,000 2023
Schedules of Fair Values and Locations of Derivative Instruments	The following table presents the fair values and locations of derivative instruments recorded on the Consolidated Balance Sheets as of December 31, 2021 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Gross Collateral Net Asset Foreign currency exchange derivatives Other current liabilities $ — $ ( 19 ) $ — $ ( 19 ) Interest rate swap derivatives Other property and investments-net and other non-current assets 1,149 — — 1,149 Other current liabilities 1,170 ( 25,196 ) — ( 24,026 ) Other non-current liabilities and deferred credits — ( 78 ) — ( 78 ) Energy commodity derivatives Other current assets 1,506 ( 107 ) — 1,399 Other property and investments-net and other 6,844 ( 5,335 ) — 1,509 Other current liabilities 25,771 ( 39,616 ) 9,089 ( 4,756 ) Other non-current liabilities and deferred credits 141 ( 4,589 ) — ( 4,448 ) Total derivative instruments recorded on the $ 36,581 $ ( 74,940 ) $ 9,089 $ ( 29,270 ) The following table presents the fair values and locations of derivative instruments recorded on the Consolidated Balance Sheets as of December 31, 2020 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Gross Collateral Net Asset Foreign currency exchange derivatives Other current assets $ 30 $ — $ — $ 30 Interest rate swap derivatives Other current liabilities — ( 19,575 ) 8,050 ( 11,525 ) Other non-current liabilities and deferred credits 952 ( 32,190 ) — ( 31,238 ) Energy commodity derivatives Other current assets 9,203 ( 8,306 ) — 897 Other property and investments-net and other 1,755 ( 1,159 ) — 596 Other current liabilities 11,037 ( 14,007 ) 487 ( 2,483 ) Other non-current liabilities and deferred credits 1,725 ( 8,043 ) 129 ( 6,189 ) Total derivative instruments recorded on the $ 24,702 $ ( 83,280 ) $ 8,666 $ ( 49,912 )
Schedule of Collateral Outstanding Related to Derivative Instruments	The following table presents Avista Corp.'s collateral outstanding related to its derivative instruments as of December 31 (in thousands): 2021 2020 Energy commodity derivatives Cash collateral posted $ 30,567 $ 4,953 Letters of credit outstanding 34,000 23,500 Balance sheet offsetting (cash collateral against net derivative positions) 9,089 616 Interest rate swap derivatives Cash collateral posted (offset by net derivative positions) — 8,050 There were no letters of credit outstanding related to interest rate swap derivatives as of December 31, 2021 and December 31, 2020. 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 December 31 (in thousands): 2021 2020 Interest rate swap derivatives Liabilities with credit-risk-related contingent features $ 25,274 $ 50,813 Additional collateral to post 25,274 42,763

Jointly Owned Electric Facili_2

Jointly Owned Electric Facilities (Tables)	12 Months Ended
	Dec. 31, 2021
Jointly Owned Utility Plant, Net Ownership Amount [Abstract]
Schedule of Utility Plant in Service for Colstrip And Accumulated Depreciation	The Company’s share of utility plant in service for Colstrip and accumulated depreciation (inclusive of the ARO assets and accumulated amortization) were as follows as of December 31 (dollars in thousands): 2021 2020 Utility plant in service $ 395,028 $ 391,922 Accumulated depreciation ( 302,220 ) ( 284,282 )

Property, Plant And Equipment (

Property, Plant And Equipment (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Schedule of Net Utility Property	Net utility property consisted of the following as of December 31 (dollars in thousands): 2021 2020 Utility plant in service $ 7,166,580 $ 6,809,797 Construction work in progress 205,405 175,767 Total 7,371,985 6,985,564 Less: Accumulated depreciation and amortization 2,146,470 1,993,952 Total net utility property $ 5,225,515 $ 4,991,612
Summary of Ratio of Depreciation to Average Depreciable Property and Average Service Lives for Utility Plan in Service	For utility operations, the ratio of depreciation provisions to average depreciable property was as follows for the years ended December 31: 2021 2020 2019 Avista Utilities Ratio of depreciation to average depreciable property 3.54 % 3.43 % 3.28 % Alaska Electric Light and Power Company Ratio of depreciation to average depreciable property 2.77 % 2.77 % 2.48 % The average service lives for the following broad categories of utility plant in service are (in years): Avista Utilities Alaska Electric Light Electric thermal/other production 26 42 Hydroelectric production 81 42 Electric transmission 50 43 Electric distribution 39 40 Natural gas distribution property 44 N/A Other shorter-lived general plant 8 18 The gross balances of the major classifications of property, plant and equipment are detailed in the following table as of December 31 (dollars in thousands): 2021 2020 Avista Utilities: Electric production $ 1,494,371 $ 1,457,497 Electric transmission 945,624 862,987 Electric distribution 2,093,937 1,978,868 Electric construction work-in-progress (CWIP) and other 424,733 384,372 Electric total 4,958,665 4,683,724 Natural gas underground storage 55,684 53,351 Natural gas distribution 1,356,477 1,282,563 Natural gas CWIP and other 87,852 83,644 Natural gas total 1,500,013 1,419,558 Common plant (including CWIP) 740,339 712,609 Total Avista Utilities 7,199,017 6,815,891 AEL&P: Electric production 106,094 105,076 Electric transmission 22,691 22,419 Electric distribution 27,138 25,814 Electric CWIP and other 7,319 6,677 Electric total 163,242 159,986 Common plant 9,726 9,687 Total AEL&P 172,968 169,673 Total gross utility property 7,371,985 6,985,564 Other (1) 17,818 16,394 Total $ 7,389,803 $ 7,001,958 (1) Included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets. Accumulated depreciation was $ 2.3 million as of December 31, 2021 and $ 2.2 million as of December 31, 2020 for the other businesses.

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2021
Asset Retirement Obligation Disclosure [Abstract]
Schedule of Changes in Asset Retirement Obligation	The following table documents the changes in the Company’s asset retirement obligation during the years ended December 31 (dollars in thousands): 2021 2020 2019 Asset retirement obligation at beginning of year $ 17,194 $ 20,338 $ 18,266 Liabilities incurred 825 ( 2,315 ) 2,699 Liabilities settled ( 1,541 ) ( 1,645 ) ( 1,503 ) Accretion expense 664 816 876 Asset retirement obligation at end of year $ 17,142 $ 17,194 $ 20,338

Pension Plans and Other Postr_2

Pension Plans and Other Postretirement Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2021
Change in Benefit Obligation and Plan Assets	The following table sets forth the pension and other postretirement benefit plan disclosures as of December 31, 2021 and 2020 and the components of net periodic benefit costs for the years ended December 31, 2021, 2020 and 2019 (dollars in thousands): Pension Benefits Other Post- 2021 2020 2021 2020 Change in benefit obligation: Benefit obligation as of beginning of year $ 826,915 $ 742,382 $ 161,233 $ 159,296 Service cost 25,306 22,392 4,114 3,902 Interest cost 26,160 27,853 5,139 6,042 Actuarial (gain)/loss ( 13,997 ) 74,688 2,808 ( 2,589 ) Benefits paid ( 65,342 ) ( 40,400 ) ( 5,696 ) ( 5,418 ) Benefit obligation as of end of year $ 799,042 $ 826,915 $ 167,598 $ 161,233 Change in plan assets: Fair value of plan assets as of beginning of year $ 722,024 $ 642,063 $ 52,173 $ 44,853 Actual return on plan assets 50,370 96,591 7,371 7,320 Employer contributions 42,000 22,000 — — Benefits paid ( 63,431 ) ( 38,630 ) — — Fair value of plan assets as of end of year $ 750,963 $ 722,024 $ 59,544 $ 52,173 Funded status $ ( 48,079 ) $ ( 104,891 ) $ ( 108,054 ) $ ( 109,060 ) Amounts recognized in the Consolidated Balance Sheets: Other current liabilities $ ( 1,951 ) $ ( 1,943 ) $ ( 684 ) $ ( 669 ) Non-current liabilities ( 46,128 ) ( 102,948 ) ( 107,370 ) ( 108,391 ) Net amount recognized $ ( 48,079 ) $ ( 104,891 ) $ ( 108,054 ) $ ( 109,060 ) Accumulated pension benefit obligation $ 685,493 $ 710,023 Accumulated postretirement benefit obligation: For retirees $ 78,347 $ 75,876 For fully eligible employees $ 32,144 $ 32,097 For other participants $ 57,107 $ 53,260 Included in accumulated other comprehensive loss (income) (net of tax): Unrecognized prior service cost (credit) $ 1,699 $ 1,902 $ ( 2,741 ) $ ( 3,570 ) Unrecognized net actuarial loss 94,109 119,318 48,872 53,737 Total 95,808 121,220 46,131 50,167 Less regulatory asset ( 85,550 ) ( 108,301 ) ( 45,350 ) ( 48,708 ) Accumulated other comprehensive loss for unfunded benefit $ 10,258 $ 12,919 $ 781 $ 1,459 Pension Benefits Other Post- 2021 2020 2021 2020 Weighted-average assumptions as of December 31: Discount rate for benefit obligation 3.39 % 3.25 % 3.40 % 3.27 % Discount rate for annual expense 3.25 % 3.85 % 3.27 % 3.89 % Expected long-term return on plan assets 5.40 % 5.50 % 4.60 % 5.30 % Rate of compensation increase 4.66 % 4.74 % Medical cost trend pre-age 65 – initial 6.00 % 6.25 % Medical cost trend pre-age 65 – ultimate 5.00 % 5.00 % Ultimate medical cost trend year pre-age 65 2026 2026 Medical cost trend post-age 65 – initial 6.00 % 6.25 % Medical cost trend post-age 65 – ultimate 5.00 % 5.00 % Ultimate medical cost trend year post-age 65 2026 2026
Components of Net Periodic Benefit Cost	Pension Benefits Other Post-retirement Benefits 2021 2020 2019 2021 2020 2019 Components of net periodic benefit cost: Service cost (a) $ 25,306 $ 22,392 $ 19,755 $ 4,114 $ 3,902 $ 3,006 Interest cost 26,160 27,853 28,417 5,139 6,042 5,598 Expected return on plan assets ( 39,088 ) ( 34,886 ) ( 31,763 ) ( 2,400 ) ( 2,377 ) ( 2,101 ) Amortization of prior service cost (credit) 257 257 257 ( 921 ) ( 958 ) ( 981 ) Net loss recognition 6,645 6,717 10,216 3,865 4,871 4,013 Net periodic benefit cost $ 19,280 $ 22,333 $ 26,882 $ 9,797 $ 11,480 $ 9,535 (a) 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.
Schedule of Allocation of Plan Assets	The target investment allocation percentages by asset classes are indicated in the table below: 2021 2020 Equity securities 55 % 35 % Debt securities 40 % 49 % Real estate 5 % 7 % Absolute return 0 % 9 %
Employer Matching Contributions	Employer matching contributions were as follows for the years ended December 31 (dollars in thousands): 2021 2020 2019 Employer 401(k) matching contributions $ 11,671 $ 11,742 $ 10,412
Deferred Compensation Assets and Liabilities	There were deferred compensation assets included in other property and investments-net and corresponding deferred compensation liabilities included in other non-current liabilities and deferred credits on the Consolidated Balance Sheets of the following amounts as of December 31 (dollars in thousands): 2021 2020 Deferred compensation assets and liabilities $ 9,513 $ 9,174
Pension Plan And SERP [Member]
Schedule of Expected Benefit Payments	The Company expects that benefit payments under the pension plan and the SERP will total (dollars in thousands): 2022 2023 2024 2025 2026 Total 2027- Expected benefit payments $ 43,282 $ 43,218 $ 43,675 $ 44,319 $ 43,810 $ 228,585
Schedule of Allocation of Plan Assets	The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of the pension plan’s assets measured and reported as of December 31, 2021 at fair value (dollars in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ — $ 6,259 $ — $ 6,259 Fixed income securities: U.S. government issues — 19,310 — 19,310 Corporate issues — 233,496 — 233,496 International issues — 34,270 — 34,270 Municipal issues — 18,558 — 18,558 Mutual funds: U.S. equity securities 236,552 — — 236,552 International equity securities 112,873 — — 112,873 Plan assets measured at NAV (not subject to hierarchy Common/collective trusts: Real estate — — — 31,040 Partnership/closely held investments: Absolute return (1) — — — 363 International equity securities — — — 50,427 Real estate — — — 7,815 Total $ 349,425 $ 311,893 $ — $ 750,963 The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of the pension plan’s assets measured and reported as of December 31, 2020 at fair value (dollars in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ — $ 3,309 $ — $ 3,309 Fixed income securities: U.S. government issues — 10,990 — 10,990 Corporate issues — 279,857 — 279,857 International issues — 39,634 — 39,634 Municipal issues — 22,431 — 22,431 Mutual funds: U.S. equity securities 146,375 — — 146,375 International equity securities 96,311 — — 96,311 Absolute return (1) 11,640 — — 11,640 Plan assets measured at NAV (not subject to hierarchy Common/collective trusts: Real estate — — — 29,532 Partnership/closely held investments: Absolute return (1) — — — 47,188 International equity securities — — — 26,760 Real estate — — — 7,997 Total $ 254,326 $ 356,221 $ — $ 722,024 (1) This category invests in multiple strategies to diversify risk and reduce volatility. The strategies include: (a) event driven, relative value, convertible, and fixed income arbitrage, (b) distressed investments, (c) long/short equity and fixed income and (d) market neutral strategies.
Other Postretirement Benefits [Member]
Schedule of Expected Benefit Payments	The Company expects that benefit payments under other postretirement benefit plans will total (dollars in thousands): 2022 2023 2024 2025 2026 Total 2027- Expected benefit payments $ 6,960 $ 7,140 $ 7,291 $ 7,453 $ 7,560 $ 39,646
Schedule of Allocation of Plan Assets	The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of other postretirement plan assets measured and reported as of December 31, 2021 at fair value (dollars in thousands): Level 1 Level 2 Level 3 Total Balanced index mutual fund (1) $ 59,545 $ — $ — $ 59,545 The following table discloses by level within the fair value hierarchy (see Note 18 for a description of the fair value hierarchy) of other postretirement plan assets measured and reported as of December 31, 2020 at fair value (dollars in thousands): Level 1 Level 2 Level 3 Total Balanced index mutual fund (1) $ 52,173 $ — $ — $ 52,173 (1) The balanced index fund for 2021 and 2020 is a single mutual fund that includes a percentage of U.S. equity and fixed income securities and International equity and fixed income securities.

Accounting For Income Taxes (Ta

Accounting For Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense	2021 2020 2019 Current income tax expense (benefit) $ 807 $ ( 37,913 ) $ 16,276 Deferred income tax expense 11,224 44,964 15,098 Total income tax expense $ 12,031 $ 7,051 $ 31,374
Schedule of Effective Income Tax Rate Reconciliation	2021 2020 2019 Federal income taxes at statutory rates $ 33,467 21.0 % $ 28,673 21.0 % $ 47,909 21.0 % Increase (decrease) in tax resulting from: Tax effect of regulatory treatment of utility ( 13,820 ) ( 8.7 ) ( 12,893 ) ( 9.4 ) ( 9,967 ) ( 4.3 ) State income tax expense 1,385 0.8 814 0.6 1,465 0.6 Acquisition costs — — — — ( 1,712 ) ( 0.7 ) Flow through related to deduction of meters ( 8,678 ) ( 5.4 ) — — — — Non-plant excess deferred turnaround (2) — — ( 8,476 ) ( 6.2 ) ( 5,690 ) ( 2.5 ) Tax loss on sale of METALfx — — — — ( 1,272 ) ( 0.6 ) Customer refunds related to prior years at 35 percent — — ( 1,189 ) ( 0.9 ) — — Other ( 323 ) ( 0.2 ) 122 0.1 641 0.3 Total income tax expense $ 12,031 7.5 % $ 7,051 5.2 % $ 31,374 13.8 % (1) With the approval of the Idaho and Washington general rate cases in 2021, a change in tax methodology resulted in recognizing a flow through benefit related to meters and mixed service costs. (2) In March 2020, the WUTC approved an all-party settlement agreement related to electric tax benefits that were set aside for Colstrip in the 2020 general rate case order. In the approved settlement agreement, the parties agreed to utilize $ 10.9 million ($ 8.4 million when tax-effected) of the electric benefits to offset costs associated with accelerating the depreciation of Colstrip Units, to reflect a remaining useful life through December 31, 2025. In the second quarter of 2020, the Company recorded a one-time increase to depreciation expense with an offsetting decrease to income tax expense. In March 2019, the IPUC approved an all-party settlement agreement related to electric tax benefits that were set aside for Colstrip in the 2020 general rate case order. In the approved settlement agreement, the parties agreed to utilize $ 6.4 million ($ 5.1 million when tax-effected) of the electric benefits to offset costs associated with accelerating the depreciation of Colstrip, to reflect a remaining useful life through December 31, 2027. In the second quarter of 2019, the Company recorded a one-time increase to depreciation expense with an offsetting decrease to income tax expense.
Schedule of Deferred Income Tax Assets and Liabilities	The total net deferred income tax liability consisted of the following as of December 31 (dollars in thousands): 2021 2020 Deferred income tax assets: Regulatory liabilities $ 200,513 $ 179,871 Tax credits and NOL carryforwards 64,994 57,516 Provisions for pensions 25,650 37,501 Other 38,181 42,641 Total gross deferred income tax assets 329,338 317,529 Valuation allowances for deferred tax assets ( 9,626 ) ( 10,021 ) Total deferred income tax assets after valuation allowances 319,712 307,508 Deferred income tax liabilities: Utility property, plant, and equipment 688,856 666,639 Regulatory assets 264,978 232,697 Other 8,587 2,884 Total deferred income tax liabilities 962,421 902,220 Net long-term deferred income tax liability $ 642,709 $ 594,712

Energy Purchase Contracts (Tabl

Energy Purchase Contracts (Tables)	12 Months Ended
	Dec. 31, 2021
Energy Purchase Contracts [Line Items]
Schedule of Utility Total Expenses	Total expenses for power purchased, natural gas purchased, fuel for generation and other fuel costs, which are included in utility resource costs in the Consolidated Statements of Income, were as follows for the years ended December 31 (dollars in thousands): 2021 2020 2019 Utility power resources $ 431,199 $ 324,297 $ 376,769
Future Contractual Commitments for Power Resources and Natural Gas Resources	The following table details Avista Utilities’ future contractual commitments for power resources (including transmission contracts) and natural gas resources (including transportation contracts) (dollars in thousands): 2022 2023 2024 2025 2026 Thereafter Total Power resources $ 198,052 $ 187,552 $ 200,693 $ 193,877 $ 184,230 $ 1,888,038 $ 2,852,442 Natural gas resources 87,228 66,508 42,581 36,423 32,094 382,981 647,815 Total $ 285,280 $ 254,060 $ 243,274 $ 230,300 $ 216,324 $ 2,271,019 $ 3,500,257
Contractual Obligations [Member]
Energy Purchase Contracts [Line Items]
Future Contractual Commitments for Power Resources and Natural Gas Resources	The following table details future contractual commitments under these agreements (dollars in thousands): 2022 2023 2024 2025 2026 Thereafter Total Contractual obligations $ 28,912 $ 29,680 $ 30,471 $ 31,287 $ 32,127 $ 212,852 $ 365,329

Committed Lines of Credit (Tabl

Committed Lines of Credit (Tables)	12 Months Ended
	Dec. 31, 2021
Avista Utilities [Member]
Line of Credit Facility [Line Items]
Schedule of Balances Outstanding and Interest Rates of Borrowings	Balances outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed lines of credit were as follows as of December 31 (dollars in thousands): 2021 2020 Balance outstanding at end of period $ 284,000 $ 102,000 Letters of credit outstanding at end of period $ 34,000 $ 27,618 Average interest rate at end of period 1.11 % 1.22 %

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2021
Long-term Debt, Unclassified [Abstract]
Schedule of Long-term Debt Instruments	Maturity Description Interest 2021 2020 Avista Corp. Secured Long-Term Debt 2022 First Mortgage Bonds 5.13 % 250,000 250,000 2023 Secured Medium-Term Notes 7.18 %- 7.54 % 13,500 13,500 2028 Secured Medium-Term Notes 6.37 % 25,000 25,000 2032 Secured Pollution Control Bonds (1) (1) 66,700 66,700 2034 Secured Pollution Control Bonds (1) (1) 17,000 17,000 2035 First Mortgage Bonds 6.25 % 150,000 150,000 2037 First Mortgage Bonds 5.70 % 150,000 150,000 2040 First Mortgage Bonds 5.55 % 35,000 35,000 2041 First Mortgage Bonds 4.45 % 85,000 85,000 2044 First Mortgage Bonds 4.11 % 60,000 60,000 2045 First Mortgage Bonds 4.37 % 100,000 100,000 2047 First Mortgage Bonds 4.23 % 80,000 80,000 2047 First Mortgage Bonds 3.91 % 90,000 90,000 2048 First Mortgage Bonds 4.35 % 375,000 375,000 2049 First Mortgage Bonds 3.43 % 180,000 180,000 2050 First Mortgage Bonds 3.07 % 165,000 165,000 2051 First Mortgage Bonds 3.54 % 175,000 175,000 2051 First Mortgage Bonds (2) 2.90 % 140,000 — Total Avista Corp. secured long-term debt 2,157,200 2,017,200 Alaska Electric Light and Power Company Secured Long-Term Debt 2044 First Mortgage Bonds 4.54 % 75,000 75,000 Total secured long-term debt 2,232,200 2,092,200 Alaska Energy and Resources Company Unsecured Long-Term Debt 2024 Unsecured Term Loan 3.44 % 15,000 15,000 Total secured and unsecured long-term debt 2,247,200 2,107,200 Other Long-Term Debt Components Unamortized debt discount ( 632 ) ( 710 ) Unamortized long-term debt issuance costs ( 14,498 ) ( 14,256 ) Total 2,232,070 2,092,234 Secured Pollution Control Bonds held by Avista ( 83,700 ) ( 83,700 ) Current portion of long-term debt ( 250,000 ) — Total long-term debt $ 1,898,370 $ 2,008,534 (1) In December 2010, $ 66.7 million and $ 17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new variable rate bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Consolidated Balance Sheets. (2) In September 2021, the Company issued and sold $ 70.0 million of 2.90 percent first mortgage bonds due in 2051 pursuant to a bond purchase agreement with institutional investors in the private placement market. In December 2021, the Company issued and sold the remaining $ 70.0 million of bonds pursuant to the same agreement. The total net proceeds from the sale of the bonds were used to repay a portion of the outstanding balance under Avista Corp.'s $ 400.0 million committed line of credit. In connection with the pricing of the first mortgage bonds in September 2021, the Company cash settled four interest rate swap derivatives (notional aggregate amount of $ 45.0 million) and paid a net amount of $ 17.2 million. See Note 7 for a discussion of interest rate swap derivatives.
Schedule of Maturities of Long-term Debt	2022 2023 2024 2025 2026 Thereafter Total Debt maturities $ 250,000 $ 13,500 $ 15,000 $ — $ — $ 1,936,547 $ 2,215,047

Long- Term Debt to Affiliated_2

Long- Term Debt to Affiliated Trust (Tables)	12 Months Ended
	Dec. 31, 2021
Long Term Debt To Affiliated Trust [Abstract]
Schedule Of Distribution Rates Paid	The distribution rates paid were as follows during the years ended December 31: 2021 2020 2019 Low distribution rate 0.99 % 1.10 % 2.79 % High distribution rate 1.10 % 2.79 % 3.61 % Distribution rate at the end of the year 1.05 % 1.10 % 2.79 %

Fair Value (Tables)

Fair Value (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Carrying Value and Estimated Fair Value of Financial Instruments	The following table sets forth the carrying value and estimated fair value of the Company’s financial instruments not reported at estimated fair value on the Consolidated Balance Sheets as of December 31 (dollars in thousands): 2021 2020 Carrying Estimated Carrying Estimated Long-term debt (Level 2) $ 963,500 $ 1,157,651 $ 963,500 $ 1,189,824 Long-term debt (Level 3) 1,200,000 1,366,619 1,060,000 1,235,248 Snettisham finance lease obligation (Level 3) 48,815 54,000 51,750 58,700 Long-term debt to affiliated trusts (Level 3) 51,547 43,299 51,547 43,815
Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis	The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Consolidated Balance Sheets as of December 31, 2021 at fair value on a recurring basis (dollars in thousands): Level 1 Level 2 Level 3 Counterparty Total December 31, 2021 Assets: Energy commodity derivatives $ — $ 34,119 $ — $ ( 31,211 ) $ 2,908 Level 3 energy commodity derivatives: Natural gas exchange agreements — — 143 ( 143 ) — Interest rate swap derivatives — 2,319 — ( 1,170 ) 1,149 Deferred compensation assets: Mutual Funds: Fixed income securities (2) 1,809 — — — 1,809 Equity securities (2) 7,594 — — — 7,594 Total $ 9,403 $ 36,438 $ 143 $ ( 32,524 ) $ 13,460 Liabilities: Energy commodity derivatives $ — $ 41,733 $ — $ ( 40,300 ) $ 1,433 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 7,914 ( 143 ) 7,771 Foreign currency exchange derivatives — 19 — — 19 Interest rate swap derivatives — 25,274 — ( 1,170 ) 24,104 Total $ — $ 67,026 $ 7,914 $ ( 41,613 ) $ 33,327 The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Consolidated Balance Sheets as of December 31, 2020 at fair value on a recurring basis (dollars in thousands): Level 1 Level 2 Level 3 Counterparty Total December 31, 2020 Assets: Energy commodity derivatives $ — $ 23,645 $ — $ ( 22,152 ) $ 1,493 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 75 ( 75 ) — Foreign currency exchange derivatives — 30 — — 30 Interest rate swap derivatives — 952 — ( 952 ) — Deferred compensation assets: Mutual Funds: Fixed income securities (2) 2,471 — — — 2,471 Equity securities (2) 6,228 — — — 6,228 Total $ 8,699 $ 24,627 $ 75 $ ( 23,179 ) $ 10,222 Liabilities: Energy commodity derivatives $ — $ 23,030 $ — $ ( 22,768 ) $ 262 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 8,485 ( 75 ) 8,410 Interest rate swap derivatives — 51,765 — ( 9,002 ) 42,763 Total $ — $ 74,795 $ 8,485 $ ( 31,845 ) $ 51,435 (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 Consolidated Balance Sheets .
Schedule of Quantitative Information	The following table presents the quantitative information which was used to estimate the fair values of the Level 3 assets and liabilities above as of December 31, 2021 (dollars in thousands): Fair Value (Net) at December 31, 2021 Valuation Technique Unobservable Input Range Natural gas exchange ( 7,771 ) Internally derived Forward purchase prices $ 2.35 - $ 4.08 /mmBTU 2.96 Weighted Average Forward sales prices $ 2.38 - $ 9.50 /mmBTU 4.51 Weighted Average Purchase volumes 130,000 - 310,000 mmBTUs Sales volumes 25,000 - 310,000 mmBTUs
Schedule of Activity For Energy Commodity Derivative Assets (Liabilities) Measured At Fair Value Using Significant Unobservable Inputs (Level 3)	The following table presents activity for energy commodity derivative assets (liabilities) measured at fair value using significant unobservable inputs (Level 3) for the years ended December 31 (dollars in thousands): Natural Gas Power Total Year ended December 31, 2021: Balance as of January 1, 2021 $ ( 8,410 ) $ — $ ( 8,410 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets (1) 4,292 — 4,292 Settlements ( 3,653 ) — ( 3,653 ) Ending balance as of December 31, 2021 (2) $ ( 7,771 ) $ — $ ( 7,771 ) Year ended December 31, 2020: Balance as of January 1, 2020 $ ( 2,976 ) $ — $ ( 2,976 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets (1) ( 4,311 ) — ( 4,311 ) Settlements ( 1,123 ) — ( 1,123 ) Ending balance as of December 31, 2020 (2) $ ( 8,410 ) $ — $ ( 8,410 ) Year ended December 31, 2019: Balance as of January 1, 2019 $ ( 2,774 ) $ ( 2,488 ) $ ( 5,262 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets (1) 8,175 435 8,610 Settlements ( 8,377 ) 2,053 ( 6,324 ) Ending balance as of December 31, 2019 (2) $ ( 2,976 ) $ — $ ( 2,976 ) (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.
Schedule of Nonrecurring Fair Value Measurements	Nonrecurring Fair Value Measurements The Company holds equity investments without a readily determinable fair value, and these assets are recorded at fair value and adjusted on a nonrecurring basis as a result of observable changes in fair value using the measurement alternative. Amounts recognized in the consolidated financial statements related to equity investments without readily determinable fair value include the following (dollars in thousands): December 31, 2021 December 31, 2020 Carrying Value (1) $ 24,161 $ 15,110 Gains (losses) 8,761 925 (1) Carrying value is adjusted to fair value as of the measurement date when observable changes in fair value occur, such as a transaction involving the underlying asset. These assets are measured using a market approach and are level 2 assets.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2021
Accumulated Other Comprehensive Loss [Abstract]
Schedule of Accumulated Other Comprehensive Loss, Net of Tax	Accumulated other comprehensive loss, net of tax, consisted of the following as of December 31 (dollars in thousands): 2021 2020 Unfunded benefit obligation for pensions and other postretirement benefit 2,934 and $ 3,822 , respectively $ 11,039 $ 14,378
Reclassification out of Accumulated Other Comprehensive Income	The following table details the reclassifications out of accumulated other comprehensive loss by component for the years ended December 31 (dollars in thousands): Amounts Reclassified from Accumulated Other Details about Accumulated Other Comprehensive Loss Components 2021 2020 2019 Amortization of defined benefit pension items Amortization of net prior service cost (a) $ ( 793 ) $ ( 794 ) $ ( 794 ) Amortization of net loss (a) 38,070 5,586 17,074 Adjustment due to effects of regulation (a) ( 33,050 ) ( 10,006 ) ( 19,309 ) Total before tax (b) 4,227 ( 5,214 ) ( 3,029 ) Tax expense (b) ( 888 ) 1,095 636 Net of tax (b) $ 3,339 $ ( 4,119 ) $ ( 2,393 ) (a) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 11 for additional details). (b) Description is also the affected line item on the Consolidated Statements of Income

Earnings Per Common Share Att_2

Earnings Per Common Share Attributable to Avista Corporation Shareholders (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Earnings Per Common Share	The following table presents the computation of basic and diluted earnings per common share attributable to Avista Corp. shareholders for the years ended December 31 (in thousands, except per share amounts): 2021 2020 2019 Numerator: Net income attributable to Avista Corp. shareholders $ 147,334 $ 129,488 $ 196,979 Denominator: Weighted-average number of common shares outstanding-basic 69,951 67,962 66,205 Effect of dilutive securities: Performance and restricted stock awards 134 140 124 Weighted-average number of common shares outstanding-diluted 70,085 68,102 66,329 Earnings per common share attributable to Avista Basic $ 2.11 $ 1.91 $ 2.98 Diluted $ 2.10 $ 1.90 $ 2.97

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2021
Regulated Operations [Abstract]
Schedule of Regulatory Assets and Liabilities	The following table presents the Company’s regulatory assets and liabilities as of December 31, 2021 (dollars in thousands): Receiving 2021 2020 Remaining (1) Not (2) Current Non- Current Non- Regulatory Assets: Deferred income tax (3 ) $ 244,154 $ — $ — $ — $ 244,154 $ — $ 108,517 Pensions and other (4 ) — 165,696 — — 165,696 — 198,746 Energy commodity (5 ) — 15,385 — 12,447 2,938 2,073 5,722 Unamortized debt repurchase (6 ) 6,768 — — — 6,768 — 7,512 Settlement with 2059 38,926 — — — 38,926 — 40,043 Demand side management (3 ) — 3,974 — — 3,974 — 3,814 Decoupling surcharge 2023 24,532 — — 9,907 14,625 7,123 17,123 Utility plant to be abandoned (7 ) 26,771 — — — 26,771 — 28,916 Interest rate swaps (8 ) 158,082 — 41,672 — 199,754 — 214,851 Deferred power costs (3 ) 10,835 — — 7,334 3,501 1,775 1,562 Deferred natural gas costs (3 ) 21,027 — — 14,095 6,932 2,308 — AFUDC above FERC (11 ) 48,455 — — — 48,455 — 47,393 COVID-19 deferrals (12 ) — — 13,591 — 13,591 — 8,166 Advanced meter infrastructure (13 ) 36,008 — — — 36,008 — 26,379 Other regulatory assets (3 ) 37,045 8,563 2,925 — 48,533 394 41,699 Total regulatory assets $ 652,603 $ 193,618 $ 58,188 $ 43,783 $ 860,626 $ 13,673 $ 750,443 Regulatory Liabilities: Deferred natural gas costs (3 ) $ — $ — $ — $ — $ — $ 874 $ — Deferred power costs (3 ) 11,891 — — 6,457 5,434 20,299 17,570 Utility plant retirement costs (9 ) 350,190 — — — 350,190 — 325,832 Income tax related liabilities (3) (10) 346,847 24,411 143,862 56,331 458,789 14,952 399,677 Interest rate swaps (8 ) 13,589 — 1,473 — 15,062 — 15,046 Decoupling rebate 2022 9,308 — — 3,049 6,259 1,447 1,519 COVID-19 deferrals (12 ) — — 12,500 — 12,500 — 10,949 Other regulatory liabilities (3 ) 6,905 17,688 — 11,312 13,281 8,863 14,227 Total regulatory liabilities $ 738,730 $ 42,099 $ 157,835 $ 77,149 $ 861,515 $ 46,435 $ 784,820 (1) Earning a return includes either interest on the regulatory asset/liability or a return on the investment as a component of rate base at the allowed rate of return. (2) Expected recovery is pending regulatory treatment including regulatory assets and liabilities with prior regulatory precedence. (3) Remaining amortization period varies depending on timing of underlying transactions. (4) As the Company has historically recovered and currently recovers its pension and other postretirement benefit costs related to its regulated operations in retail rates, the Company records a regulatory asset for that portion of its pension and other postretirement benefit funding deficiency. (5) The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and losses result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho and periodic general rates cases. The resulting regulatory assets associated with energy commodity derivative instruments have been concluded to be probable of recovery through future rates. (6) Premiums paid or discounts received to repurchase debt are amortized over the remaining life of the original debt that was repurchased or, if new debt is issued in connection with the repurchase, these costs are amortized over the life of the new debt. These costs are recovered through retail rates as a component of interest expense. (7) The WUTC approved recovery of AMI project costs through the 2020 general rate case settlements, including amortization of retired meters replaced through the project through 2033. There are additional smaller projects included in the balance that the Company expects to fully recover, which have not yet been through the regulatory process. (8) For interest rate swap derivatives, Avista Corp. records all mark-to-market gains and losses in each accounting period as assets and liabilities, as well as offsetting regulatory assets and liabilities, such that there is no income statement impact. The interest rate swap derivatives are risk management tools similar to energy commodity derivatives. Upon settlement of interest rate swap derivatives, the regulatory asset or liability is amortized as a component of interest expense over the term of the associated debt. The Company records an offset of interest rate swap derivative assets and liabilities with regulatory assets and liabilities, based on the prior practice of the commissions to provide recovery through the ratemaking process. Settled interest rate swap derivatives which have been through a general rate case proceeding are classified as earning a return in the table above, whereas all unsettled interest rate swap derivatives and settled interest rate swap derivatives which have not been included in a general rate case are classified as expected recovery. (9) This amount is dependent upon the cost of removal of underlying utility plant assets and the life of utility plant. (10) The majority of this balance represents amounts due back to customers and resulted from the Tax Cuts and Jobs Act signed into law in December 2017, which changed the federal income tax rate from 35 percent to 21 percent. The Company revalued all deferred income taxes as of December 31, 2017. The Company expects the amounts for utility plant items for Avista Utilities to be returned to customers over a period of approximately 32 years . The Company expects the AEL&P amounts to be returned to customers over a period of approximately 40 years. A significant portion of the regulatory liability attributable to non-plant excess deferred taxes was used to offset a portion of the costs associated with accelerating the depreciation of Colstrip based on settlements in Washington and Idaho. (11) This amount is being amortized based on the underlying utility plant assets and the life of utility plant. (12) The WUTC, IPUC and OPUC issued accounting orders allowing the Company to defer certain costs, net of any benefits, related to the COVID-19 pandemic. The Company has recorded all benefits on a gross basis as a regulatory liability to customers and all additional allowed costs are a regulatory asset. The ratemaking treatment will be determined in future general rate cases in each jurisdiction. (13) This amount represents the deferral of the depreciation expense of the Company’s AMI project in Washington state. Recovery of these amounts was approved by WUTC in the 2021 general rate case order.
Schedule of Decoupling and Earnings Sharing Mechanisms	As of December 31, 2021 and December 31, 2020, the Company had the following cumulative balances outstanding related to decoupling and earnings sharing mechanisms in its various jurisdictions (dollars in thousands): December 31, December 31, 2021 2020 Washington Decoupling surcharge $ 13,522 $ 21,340 Idaho Decoupling (rebate) surcharge $ ( 1,450 ) $ 1,202 Provision for earnings sharing rebate ( 686 ) ( 686 ) Oregon Decoupling surcharge (rebate) $ 3,152 $ ( 1,262 )

Information by Business Segme_2

Information by Business Segments (Tables)	12 Months Ended
	Dec. 31, 2021
Segment Reporting [Abstract]
Schedule of Business Segments	The following table presents information for each of the Company’s business segments (dollars in thousands): Avista Alaska Total Utility Other Intersegment Total For the year ended Operating revenues $ 1,392,999 $ 45,366 $ 1,438,365 $ 571 $ — $ 1,438,936 Resource costs 493,289 3,834 497,123 — — 497,123 Other operating expenses 352,241 13,884 366,125 5,927 — 372,052 Depreciation and amortization 221,552 10,363 231,915 261 — 232,176 Income (loss) from operations 217,663 16,186 233,849 ( 5,617 ) — 228,232 Interest expense (2) 99,629 6,096 105,725 522 ( 95 ) 106,152 Income taxes 6,029 2,763 8,792 3,239 — 12,031 Net income from continuing 125,558 7,224 132,782 14,552 — 147,334 Capital expenditures (3) 435,887 4,052 439,939 1,270 — 441,209 For the year ended Operating revenues $ 1,277,468 $ 42,809 $ 1,320,277 $ 1,614 $ — $ 1,321,891 Resource costs 396,543 1,966 398,509 — — 398,509 Other operating expenses 341,709 12,905 354,614 5,344 — 359,958 Depreciation and amortization 213,701 9,806 223,507 716 — 224,223 Income (loss) from operations 220,058 17,088 237,146 ( 4,446 ) — 232,700 Interest expense (2) 98,451 6,272 104,723 524 ( 186 ) 105,061 Income taxes 4,921 3,011 7,932 ( 881 ) — 7,051 Net income (loss) from 124,810 8,095 132,905 ( 3,417 ) — 129,488 Capital expenditures (3) 397,292 7,014 404,306 1,368 — 405,674 For the year ended Operating revenues $ 1,295,873 $ 37,265 $ 1,333,138 $ 12,484 $ — $ 1,345,622 Resource costs 442,471 ( 2,654 ) 439,817 — — 439,817 Other operating expenses (4) 352,170 12,717 364,887 18,883 — 383,770 Depreciation and amortization 195,697 9,668 205,365 629 — 205,994 Income (loss) from operations 200,994 16,423 217,417 ( 7,028 ) — 210,389 Interest expense (2) 97,866 6,385 104,251 1,032 ( 929 ) 104,354 Income taxes 28,363 2,816 31,179 195 — 31,374 Net income from continuing 183,977 7,458 191,435 5,544 — 196,979 Capital expenditures (3) 434,077 8,433 442,510 835 — 443,345 Total Assets: As of December 31, 2021 $ 6,458,244 $ 265,422 $ 6,723,666 $ 132,158 $ ( 2,241 ) $ 6,853,583 As of December 31, 2020 $ 6,035,340 $ 268,971 $ 6,304,311 $ 109,658 $ ( 11,872 ) $ 6,402,097 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. Intersegment eliminations reported as assets represent intersegment accounts receivable. (2) Including interest expense to affiliated trusts. (3) The capital expenditures for the other businesses are included in other investing activities on the Consolidated Statements of Cash Flows. (4) Other operating expenses for Avista Utilities for 2019 include merger transaction costs which are separately disclosed on the Consolidated Statements of Income.

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Summary of Ratio of Depreciation to Average Depreciable Property and Average Service Lives for Utility Plan in Service (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Avista Utilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Ratio of depreciation to average depreciable property	3.54%	3.43%	3.28%
Avista Utilities [Member] | Electric Thermal [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	26 years
Avista Utilities [Member] | Hydroelectric Production [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	81 years
Avista Utilities [Member] | Electric Transmission [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	50 years
Avista Utilities [Member] | Electric Distribution [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	39 years
Avista Utilities [Member] | Natural Gas Distribution [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	44 years
Avista Utilities [Member] | Other Plant in Service [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	8 years
Alaska Electric Light & Power [Member]
Summary Of Significant Accounting Policies [Line Items]
Ratio of depreciation to average depreciable property	2.77%	2.77%	2.48%
Alaska Electric Light & Power [Member] | Electric Thermal [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	42 years
Alaska Electric Light & Power [Member] | Hydroelectric Production [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	42 years
Alaska Electric Light & Power [Member] | Electric Transmission [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	43 years
Alaska Electric Light & Power [Member] | Electric Distribution [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	40 years
Alaska Electric Light & Power [Member] | Other Plant in Service [Member]
Summary Of Significant Accounting Policies [Line Items]
Average service lives for the utility plan in service	18 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Effective AFUDC Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Avista Utilities [Member]
Effective Rate On Allowance For Funds Used During Construction [Line Items]
Effective state AFUDC rate	7.19%	7.25%	7.39%
Alaska Electric Light & Power [Member]
Effective Rate On Allowance For Funds Used During Construction [Line Items]
Effective state AFUDC rate	8.90%	8.04%	8.96%

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policies [Line Items]
Unrecognized tax benefits, income tax penalties and interest expense	$ 0	$ 0	$ 0
Restricted Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Award vesting period	3 years
Total Shareholder Return Market-Based Awards and Performance Awards [Member]
Summary Of Significant Accounting Policies [Line Items]
Award vesting period	3 years
Dividend component liability, current	$ 1,500,000	$ 800,000
Total Shareholder Return Market-Based Awards and Performance Awards [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Common stock issued range, percent of the performance shares granted	0.00%
Total Shareholder Return Market-Based Awards and Performance Awards [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Common stock issued range, percent of the performance shares granted	200.00%

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4,713	$ 5,846	$ 11,353
Income tax benefits	990	1,228	2,384
Excess tax benefits (expenses) on settled share-based employee payments	$ 909	$ (165)	$ 612
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the year	62,594	45,540	50,061
Shares vested during the year	34,854	56,203	48,228
Unvested shares at end of year	96,127	71,706	93,351
Unrecognized compensation expense at end of year (in thousands)	$ 2,215	$ 2,003	$ 2,054
Total Shareholder Return Market-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the year	64,910	47,848	99,214
Shares vested during the year	77,174	71,299	106,858
Shares earned based on market metrics	58,652
Unvested shares at end of year	107,854	122,133	178,035
Unrecognized compensation expense at end of year (in thousands)	$ 2,653	$ 2,296	$ 3,377
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the year	64,910	47,848	49,609
Shares vested during the year	38,590	35,622	53,454
Shares earned based on market metrics	26,627	63,763	106,908
Unvested shares at end of year	107,854	83,464	88,990
Unrecognized compensation expense at end of year (in thousands)	$ 1,223	$ 1,090	$ 2,401

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Other Expense (Income) - Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Interest income	$ (1,943)	$ (1,952)	$ (2,587)
Interest on regulatory deferrals	(1,206)	(1,222)	(1,460)
Equity-related AFUDC	(7,004)	(6,970)	(6,585)
Non-service portion of pension and other postretirement benefit expenses	1,386	6,433	8,899
Net (income) loss on investments	(21,402)	(905)	(14,299)
Other expense (income)	(3,129)	(201)	1,104
Total	$ (33,298)	$ (4,817)	$ (14,928)

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Allowance as of the beginning of the year		$ 11,387	$ 2,419	$ 5,233
Additions expensed during the year	[1]	9,279	11,280	460
Net deductions	[2]	(10,201)	(2,312)	(3,274)
Allowance as of the end of the year		$ 10,465	$ 11,387	$ 2,419
[1]	Increases in 2021 and 2020 related to COVID-19 bad debt expense in excess of the amount recovered through rates.
[2]	Increase in 2021 relates to COVID forgiveness program.

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Parenthetical) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)
COVID-19 [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred incremental bad debt expense	$ 1.1

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Estimated Retirement Costs Collected from Customers (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Regulated Asset Liability [Line Items]
Regulatory liability for utility plant retirement costs	$ 861,515	$ 784,820
Utility Plant Retirement Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory liability for utility plant retirement costs	$ 350,190	$ 325,832

Summary of Significant Accou_12

Summary of Significant Accounting Policies - Summary of Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Line Items]
Balance as of December 31, 2020 and 2021	$ 52,426	$ 52,426
Alaska Electric Light & Power [Member]
Goodwill [Line Items]
Balance as of December 31, 2020 and 2021	52,426
Accumulated Impairment Losses [Member]
Goodwill [Line Items]
Balance as of December 31, 2020 and 2021	$ 0

Summary of Significant Accou_13

Summary of Significant Accounting Policies - Summary of Appropriated Retained Earnings Amount Included in Retained Earnings (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Appropriated Retained Earnings [Abstract]
Appropriated retained earnings	$ 53,620	$ 47,473

New Accounting Standards - Addi

New Accounting Standards - Additional Information (Details)	Dec. 31, 2021
ASU No. 2018-13 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2020
Change in accounting principle, accounting standards update, immaterial effect	true
ASU No. 2018-14 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Dec. 15, 2020
Change in accounting principle, accounting standards update, immaterial effect	true

Balance Sheet Components - Mate

Balance Sheet Components - Materials and Supplies, Fuel Stock and Stored Natural Gas (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Materials and supplies	$ 62,003	$ 53,258
Fuel stock	5,126	4,658
Stored natural gas	17,604	9,535
Total	$ 84,733	$ 67,451

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$ 21,477	$ 4,336
Prepayments	24,387	24,411
Income taxes receivable	29,615	49,814
Other	5,275	6,324
Total	$ 80,754	$ 84,885

Balance Sheet Components - Othe

Balance Sheet Components - Other Property and Investments-Net and Other Non-current Assets (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Operating lease ROU assets		$ 70,133	$ 71,891
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]		Total	Total
Finance lease ROU assets		$ 43,697	$ 47,338
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]		Total	Total
Non-utility property		$ 20,033	$ 19,508
Equity investments		91,057	59,318
Investment in affiliated trust		11,547	11,547
Notes receivable		14,949	14,454
Deferred compensation assets		9,513	9,174
Assets held for sale	[1]		3,462
Other		19,614	26,947
Total		$ 280,543	$ 263,639
[1]	The Company sold certain subsidiary assets associated with Steam Plant Square and Brew Pub during 2021.

Balance Sheet Components - Ot_2

Balance Sheet Components - Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued taxes other than income taxes	$ 41,706	$ 45,099
Derivative liabilities	28,801	14,008
Employee paid time off accruals	27,741	26,495
Accrued interest	17,538	17,083
Pensions and other postretirement benefits	13,582	11,987
Other	39,493	35,159
Total	$ 168,861	$ 149,831

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Other Non-Current Liabilities and Deferred Credits (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Operating lease liabilities	$ 66,068	$ 67,716
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Total	Total
Finance lease liabilities	$ 45,730	$ 48,815
Deferred investment tax credits	29,313	29,866
Asset retirement obligations	17,142	17,194	$ 20,338	$ 18,266
Derivative liabilities	4,525	37,427
Other	15,347	13,981
Total	$ 178,125	$ 214,999

Revenue - Unbilled Accounts Rec

Revenue - Unbilled Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Unbilled accounts receivable	$ 74,479	$ 71,258

Revenue - Schedule of Utilities

Revenue - Schedule of Utilities Operating Revenue Expense Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Utility-related taxes	$ 62,736	$ 59,319	$ 59,528

Revenue - Additional Informatio

Revenue - Additional Information (Details) $ in Millions	Dec. 31, 2021USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 17.4

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 1,438,936	$ 1,321,891	$ 1,345,622
Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	413,657	396,403	386,236
Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	352,034	327,726	336,980
Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	106,756	103,103	105,802
Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	7,722	7,555	7,702
Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	880,169	834,787	836,720
Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	21,005	18,236	18,180
Other Electric Revenues from Contracts With Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	33,870	19,252	26,969
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	935,044	872,275	881,869
Avista Utilities [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,392,999	1,277,468	1,295,873
Avista Utilities [Member] | Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	394,717	377,785	369,102
Avista Utilities [Member] | Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	326,173	303,972	317,589
Avista Utilities [Member] | Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	106,756	103,103	105,802
Avista Utilities [Member] | Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	7,472	7,303	7,448
Avista Utilities [Member] | Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	835,118	792,163	799,941
Avista Utilities [Member] | Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	21,005	18,236	18,180
Avista Utilities [Member] | Other Electric Revenues from Contracts With Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	33,870	19,252	26,969
Avista Utilities [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	889,993	829,651	845,090
Avista Utilities [Member] | Residential Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	221,405	213,612	196,430
Avista Utilities [Member] | Commercial Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	100,819	94,937	92,168
Avista Utilities [Member] | Industrial and Interruptible Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	7,796	7,128	5,263
Avista Utilities [Member] | Retail Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	330,020	315,677	293,861
Avista Utilities [Member] | Transportation Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	8,547	7,917	8,674
Avista Utilities [Member] | Other Natural Gas Revenues from Contracts With Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	5,344	4,501	4,500
Avista Utilities [Member] | Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	343,911	328,095	307,035
Avista Utilities [Member] | Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues	1,233,904	1,157,746	1,152,125
Avista Utilities [Member] | Derivative revenues
Disaggregation of Revenue [Line Items]
Revenues	152,590	110,313	118,741
Avista Utilities [Member] | Alternative Revenue Programs [Member]
Disaggregation of Revenue [Line Items]
Revenues	(6,635)	(3,814)	9,614
Avista Utilities [Member] | Deferrals and Amortizations for Rate Refunds to Customers
Disaggregation of Revenue [Line Items]
Revenues	2,984	5,335	4,509
Avista Utilities [Member] | Other Utility Revenues
Disaggregation of Revenue [Line Items]
Revenues	10,156	7,888	10,884
Alaska Electric Light & Power [Member]
Disaggregation of Revenue [Line Items]
Revenues	45,366	42,809	37,265
Alaska Electric Light & Power [Member] | Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	18,940	18,618	17,134
Alaska Electric Light & Power [Member] | Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	25,861	23,754	19,391
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	250	252	254
Alaska Electric Light & Power [Member] | Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	45,051	42,624	36,779
Alaska Electric Light & Power [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	45,051	42,624	36,779
Alaska Electric Light & Power [Member] | Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues	45,051	42,624	36,779
Alaska Electric Light & Power [Member] | Deferrals and Amortizations for Rate Refunds to Customers
Disaggregation of Revenue [Line Items]
Revenues	(190)	(190)	(190)
Alaska Electric Light & Power [Member] | Other Utility Revenues
Disaggregation of Revenue [Line Items]
Revenues	505	375	676
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	571	1,614	12,484
Corporate and Other [Member] | Revenue from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues	2	564	11,286
Corporate and Other [Member] | Other Revenues
Disaggregation of Revenue [Line Items]
Revenues	$ 569	$ 1,050	$ 1,198

Leases - Additional Information

Leases - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Operating lease, existence of option to extend	true
Minimum [Member]
Lessee, Lease, Description [Line Items]
Operating lease, remaining terms of contract	1 year
Operating lease, options to extend lease term	5 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Operating lease, remaining terms of contract	72 years
Operating lease, options to extend lease term	50 years
Snettisham Hydroelectric Project [Member]
Lessee, Lease, Description [Line Items]
Finance lease expiration year	2034
State of Montana [Member] | Hydroelectric Facilities in the Clark Fork River Basin [Member]
Lessee, Lease, Description [Line Items]
Operating lease expiration year	2046
ASC 842 [Member]
Lessee, Lease, Description [Line Items]
Change in accounting principle, accounting standards update, adopted	true

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Fixed lease cost (Other operating expenses)	$ 4,970	$ 4,746
Variable lease cost (Other operating expenses)	1,180	1,099
Amortization of ROU asset (Depreciation and amortization)	3,641	3,641
Interest on lease liabilities (Interest expense)	2,522	2,662
Operating Lease [Member]
Lessee, Lease, Description [Line Items]
Lease, Cost	6,150	5,845
Finance Lease [Member]
Lessee, Lease, Description [Line Items]
Lease, Cost	$ 6,163	$ 6,303

Leases - Summary of Supplementa

Leases - Summary of Supplemental Cash Flow Information related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating cash outflows:
Operating lease payments	$ 4,805	$ 4,612
Interest on finance lease	2,522	2,662
Total operating cash outflows	7,327	7,274
Finance cash outflows:
Principal payments on finance lease	$ 2,935	$ 2,800

Leases - Summary of Supplemen_2

Leases - Summary of Supplemental Balance Sheet Information Related to Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease ROU assets	$ 70,133	$ 71,891
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other property and investments-net and other non-current assets	Other property and investments-net and other non-current assets
Operating Lease, Liability, Current	$ 4,301	$ 4,249
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Operating Lease, Liability, Noncurrent	$ 66,068	$ 67,716
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Operating Lease, Liability	$ 70,369	$ 71,965
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Liabilities	Liabilities
Finance lease ROU assets	$ 43,697	$ 47,338
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other property and investments-net and other non-current assets	Other property and investments-net and other non-current assets
Finance Lease, Liability, Current	$ 3,085	$ 2,935
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Finance Lease, Liability, Noncurrent	$ 45,730	$ 48,815
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Noncurrent	Other Liabilities, Noncurrent
Finance Lease, Liability	$ 48,815	$ 51,750
Operating leases, Weighted Average Remaining Lease Term	24 years 2 months 19 days	25 years 2 months 12 days
Finance leases, Weighted Average Remaining Lease Term	6 years 3 months 25 days	7 years 2 months 19 days
Operating leases, Weighted Average Discount Rate	4.28%	4.28%
Finance leases, Weighted Average Discount Rate	4.35%	4.62%

Leases - Summary of Maturities

Leases - Summary of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating Leases, Liability, Payments, Due year one	$ 4,820	$ 4,779
Operating Leases, Liability, Payments, Due year two	4,849	4,799
Operating Leases, Liability, Payments, Due year three	4,875	4,827
Operating Leases, Liability, Payments, Due year four	4,882	4,852
Operating Leases, Liability, Payments, Due year five	4,867	4,865
Operating Leases, Thereafter	91,845	96,734
Operating Leases, Total lease payments	116,138	120,856
Operating Leases, Less: imputed interest	(45,769)	(48,891)
Operating Leases, Total	$ 70,369	$ 71,965
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Liabilities	Liabilities
Finance Leases, Liability, Payments, Due year one	$ 5,460	$ 5,457
Finance Leases, Liability, Payments, Due year two	5,456	5,460
Finance Leases, Liability, Payments, Due year three	5,459	5,456
Finance Leases, Liability, Payments, Due year four	5,454	5,459
Finance Leases, Liability, Payments, Due year five	5,456	5,454
Finance Leases, Thereafter	38,204	43,661
Finance Leases, Total lease payments	65,489	70,947
Finance Leases, Less: imputed interest	(16,674)	(19,197)
Finance Leases, Total	$ 48,815	$ 51,750

Variable Interest Entities (Det

Variable Interest Entities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)MW	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	$ 6,853,583	$ 6,402,097	$ 6,082,456
Limited Partnerships and Similar Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	79,200
Variable Interest Entity Remaining Investment Commitment Amount	$ 27,000
Minimum [Member] | Limited Partnerships and Similar Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Restrictions on Withdrawal of Member Capital Account	2022
Maximum [Member] | Limited Partnerships and Similar Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Restrictions on Withdrawal of Member Capital Account	2040
Variable Interest Entity, Not Primary Beneficiary [Member] | Limited Partnerships and Similar Entities [Member] | VIE Commitments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	$ 75,400
Lancaster Power Purchase Agreement [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Evaluated Power Capacity | MW	270
Variable Interest Entity, Reporting Entity Involvement, Contractual Commitment, Amount	$ 143,400
Lancaster Power Purchase Agreement [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Minimum [Member]
Variable Interest Entity [Line Items]
Average service lives for the utility plan in service	15 years
Lancaster Power Purchase Agreement [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Average service lives for the utility plan in service	25 years

Derivatives and Risk Manageme_3

Derivatives and Risk Management - Schedule of Energy Commodity Derivative Volumes (Details) MWh in Thousands, MMBTU in Thousands	12 Months Ended
	Dec. 31, 2021MWhMMBTU	Dec. 31, 2020MMBTUMWh
Purchase [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MWh	129	1
Year two | MWh	0	0
Year three | MWh	0	0
Year four | MWh	0	0
Year five | MWh		0
Purchase [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MMBTU	7,114	10,353
Year two | MMBTU	378	450
Year three | MMBTU	228	0
Year four | MMBTU	0	0
Year five | MMBTU		0
Purchase [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MWh	0	224
Year two | MWh	0	0
Year three | MWh	0	0
Year four | MWh	0	0
Year five | MWh		0
Purchase [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MMBTU	61,405	65,188
Year two | MMBTU	23,218	25,525
Year three | MMBTU	3,413	4,950
Year four | MMBTU	0	0
Year five | MMBTU		0
Sales [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MWh	234	17
Year two | MWh	0	0
Year three | MWh	0	0
Year four | MWh	0	0
Year five | MWh		0
Sales [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MMBTU	3,933	5,448
Year two | MMBTU	1,360	1,360
Year three | MMBTU	1,370	1,360
Year four | MMBTU	1,115	1,370
Year five | MMBTU		1,115
Sales [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MWh	452	451
Year two | MWh	0	0
Year three | MWh	0	0
Year four | MWh	0	0
Year five | MWh		0
Sales [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MMBTU	31,485	39,273
Year two | MMBTU	9,323	12,030
Year three | MMBTU	228	900
Year four | MMBTU	0	0
Year five | MMBTU		0

Derivatives and Risk Manageme_4

Derivatives and Risk Management - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021USD ($)MMBTUMWh	Dec. 31, 2020USD ($)MMBTUMWh
Canadian [Member]
Derivative [Line Items]
Number of days Canadian currency prices are settled with U.S. dollars	60 days
Interest Rate Swap [Member]
Derivative [Line Items]
Letters of credit outstanding | $	$ 0	$ 0
Purchase [Member] | Physical [Member] | Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years | MWh	0
Expected deliveries of energy commodity derivatives after three years | MWh		0
Purchase [Member] | Physical [Member] | Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years | MMBTU	0
Expected deliveries of energy commodity derivatives after three years | MMBTU		0
Purchase [Member] | Financial [Member] | Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years | MWh	0
Expected deliveries of energy commodity derivatives after three years | MWh		0
Purchase [Member] | Financial [Member] | Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years | MMBTU	0
Expected deliveries of energy commodity derivatives after three years | MMBTU		0
Sales [Member] | Physical [Member] | Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years | MWh	0
Expected deliveries of energy commodity derivatives after three years | MWh		0
Sales [Member] | Physical [Member] | Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years | MMBTU	0
Expected deliveries of energy commodity derivatives after three years | MMBTU		0
Sales [Member] | Financial [Member] | Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years | MWh	0
Expected deliveries of energy commodity derivatives after three years | MWh		0
Sales [Member] | Financial [Member] | Gas Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after five years | MMBTU	0
Expected deliveries of energy commodity derivatives after three years | MMBTU		0

Derivatives and Risk Manageme_5

Derivatives and Risk Management - Summary of Foreign Currency Exchange Derivatives (Details) $ in Thousands, $ in Thousands	Dec. 31, 2021USD ($)DerivativeContracts	Dec. 31, 2021CAD ($)DerivativeContracts	Dec. 31, 2020USD ($)DerivativeContracts	Dec. 31, 2020CAD ($)DerivativeContracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Number of contracts | DerivativeContracts	25	25	22	22
United States of America, Dollars [Member] | Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Notional amount	$ 8,571		$ 3,860
Canada, Dollars [Member] | Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Notional amount		$ 10,957		$ 4,949

Derivatives and Risk Manageme_6

Derivatives and Risk Management - Summary of Unsettled Interest Rate Swap Derivatives (Details) - Interest Rate Swap [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)Contract	Dec. 31, 2020USD ($)Contract
2021 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts | Contract		4
Notional Amount | $		$ 45,000
Mandatory Cash Settlement Date		2021
2022 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts | Contract	13	11
Notional Amount | $	$ 140,000	$ 120,000
Mandatory Cash Settlement Date	2022	2022
2023 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts | Contract	2	1
Notional Amount | $	$ 20,000	$ 10,000
Mandatory Cash Settlement Date	2023	2023
2024 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts | Contract	1
Notional Amount | $	$ 10,000
Mandatory Cash Settlement Date	2024

Derivatives and Risk Manageme_7

Derivatives and Risk Management - Schedules of Fair Values and Locations of Derivative Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Gross Asset	$ 36,581	$ 24,702
Gross Liability	(74,940)	(83,280)
Collateral Netting	9,089	8,666
Net Asset (Liability) on Balance Sheet	(29,270)	(49,912)
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netting	9,089	616
Other Current Assets [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		30
Net Asset (Liability) on Balance Sheet		30
Other Current Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	1,506	9,203
Gross Liability	(107)	(8,306)
Net Asset (Liability) on Balance Sheet	1,399	897
Other Current Liabilities [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Liability	(19)
Net Asset (Liability) on Balance Sheet	(19)
Other Current Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	1,170
Gross Liability	(25,196)	(19,575)
Collateral Netting		8,050
Net Asset (Liability) on Balance Sheet	(24,026)	(11,525)
Other Current Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	25,771	11,037
Gross Liability	(39,616)	(14,007)
Collateral Netting	9,089	487
Net Asset (Liability) on Balance Sheet	(4,756)	(2,483)
Other Noncurrent Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		952
Gross Liability	(78)	(32,190)
Net Asset (Liability) on Balance Sheet	(78)	(31,238)
Other Noncurrent Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	141	1,725
Gross Liability	(4,589)	(8,043)
Collateral Netting		129
Net Asset (Liability) on Balance Sheet	(4,448)	(6,189)
Other Property and Investments-Net and Other Non-current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	1,149
Net Asset (Liability) on Balance Sheet	1,149
Other Property and Investments-Net and Other Non-current Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	6,844	1,755
Gross Liability	(5,335)	(1,159)
Net Asset (Liability) on Balance Sheet	$ 1,509	$ 596

Derivatives and Risk Manageme_8

Derivatives and Risk Management - Schedule of Collateral Outstanding Related to Derivative Instruments (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Balance sheet offsetting (cash collateral against net derivative positions)	$ 9,089,000	$ 8,666,000
Commodity Contracts [Member]
Derivative [Line Items]
Cash collateral posted	30,567,000	4,953,000
Letters of credit outstanding	34,000,000	23,500,000
Balance sheet offsetting (cash collateral against net derivative positions)	9,089,000	616,000
Interest Rate Swap [Member]
Derivative [Line Items]
Cash collateral posted		8,050,000
Letters of credit outstanding	0	0
Liabilities with credit-risk-related contingent features	25,274,000	50,813,000
Additional collateral to post	$ 25,274,000	$ 42,763,000

Jointly Owned Electric Facili_3

Jointly Owned Electric Facilities - Additional Information (Details)	Dec. 31, 2021
Jointly Owned Utility Plant, Net Ownership Amount [Abstract]
Owners percentage interest	15.00%

Jointly Owned Electric Facili_4

Jointly Owned Electric Facilities - Schedule of Utility Plant in Service for Colstrip And Accumulated Depreciation (Details) - Colstrip Generating Project [Member] - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Jointly Owned Utility Plant Interests [Line Items]
Utility plant in service	$ 395,028	$ 391,922
Accumulated depreciation	$ (302,220)	$ (284,282)

Property, Plant And Equipment -

Property, Plant And Equipment - Schedule of Net Utility Property (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Utility plant in service	$ 7,166,580	$ 6,809,797
Construction work in progress	205,405	175,767
Total	7,371,985	6,985,564
Less: Accumulated depreciation and amortization	2,146,470	1,993,952
Total net utility property	$ 5,225,515	$ 4,991,612

Property, Plant And Equipment_2

Property, Plant And Equipment - Schedule of Major Classifications of Property, Plant And Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Public Utility, Property, Plant and Equipment [Line Items]
Construction work-in-progress (CWIP) and other	$ 205,405	$ 175,767
Total	7,371,985	6,985,564
Other Property	280,543	263,639
Total	7,389,803	7,001,958
Avista Utilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	7,199,017	6,815,891
Common Plant	740,339	712,609
Avista Utilities [Member] | Electricity [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production	1,494,371	1,457,497
Transmission	945,624	862,987
Distribution	2,093,937	1,978,868
Construction work-in-progress (CWIP) and other	424,733	384,372
Total	4,958,665	4,683,724
Avista Utilities [Member] | Natural Gas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	1,356,477	1,282,563
Construction work-in-progress (CWIP) and other	87,852	83,644
Total	1,500,013	1,419,558
Natural gas underground storage	55,684	53,351
Alaska Electric Light & Power [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total	172,968	169,673
Common Plant	9,726	9,687
Alaska Electric Light & Power [Member] | Electricity [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Production	106,094	105,076
Transmission	22,691	22,419
Distribution	27,138	25,814
Construction work-in-progress (CWIP) and other	7,319	6,677
Total	163,242	159,986
Corporate and Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Other Property	$ 17,818	$ 16,394

Property, Plant And Equipment_3

Property, Plant And Equipment - Schedule of Major Classifications of Property, Plant And Equipment (Parenthetical) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Corporate and Other [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ 2.3	$ 2.2

Asset Retirement Obligations -

Asset Retirement Obligations - Schedule of Changes in Asset Retirement Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]
Asset retirement obligation at beginning of year	$ 17,194	$ 20,338	$ 18,266
Liabilities incurred	825	(2,315)	2,699
Liabilities settled	(1,541)	(1,645)	(1,503)
Accretion expense	664	816	876
Asset retirement obligation at end of year	$ 17,142	$ 17,194	$ 20,338

Pension Plans and Other Postr_3

Pension Plans and Other Postretirement Benefit Plans - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Payment for pension benefits	$ 42,000	$ 22,000	$ 22,000
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%
Deferred Compensation, Excluding Share-based Payments and Retirement Benefits [Member] | Executive Officer [Member]
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation, earlier of retirement, termination, disability or death, percent	75.00%
Deferred compensation incentive payments, percent	100.00%
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	55.00%	35.00%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	40.00%	49.00%
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	5.00%	7.00%
Absolute Return [Member]
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	0.00%	9.00%
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to pension plan	$ 42,000
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to pension plan	$ 7,200
Other Postretirement Benefits [Member] | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	60.00%	60.00%
Other Postretirement Benefits [Member] | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	40.00%	40.00%

Pension Plans and Other Postr_4

Pension Plans and Other Postretirement Benefit Plans - Schedule of Expected Benefit Payments (Details) $ in Thousands	Dec. 31, 2021USD ($)
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
2022	$ 43,282
2023	43,218
2024	43,675
2025	44,319
2026	43,810
Total 2027- 2031	228,585
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
2022	6,960
2023	7,140
2024	7,291
2025	7,453
2026	7,560
Total 2027- 2031	$ 39,646

Pension Plans and Other Postr_5

Pension Plans and Other Postretirement Benefit Plans - Change in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities		$ (13,582)	$ (11,987)
Non-current liabilities		(153,467)	(211,880)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans		(11,039)	(14,378)
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		826,915	742,382
Service cost	[1]	25,306	22,392	$ 19,755
Interest cost		26,160	27,853	28,417
Actuarial (gain)/loss		(13,997)	74,688
Benefits paid		(65,342)	(40,400)
Benefit obligation as of end of year		799,042	826,915	742,382
Fair value of plan assets as of beginning of year		722,024	642,063
Actual return on plan assets		50,370	96,591
Employer contributions		42,000	22,000
Benefits paid		(63,431)	(38,630)
Fair value of plan assets as of end of year		750,963	722,024	642,063
Funded status		(48,079)	(104,891)
Other current liabilities		(1,951)	(1,943)
Non-current liabilities		(46,128)	(102,948)
Net amount recognized		(48,079)	(104,891)
Accumulated pension benefit obligation		685,493	710,023
Unrecognized prior service cost (credit)		1,699	1,902
Unrecognized net actuarial loss		94,109	119,318
Total		95,808	121,220
Less regulatory asset		(85,550)	(108,301)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans		$ 10,258	$ 12,919
Discount rate for benefit obligation		3.39%	3.25%
Discount rate for annual expense		3.25%	3.85%
Expected long-term return on plan assets		5.40%	5.50%
Rate of compensation increase		4.66%	4.74%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		$ 161,233	$ 159,296
Service cost	[1]	4,114	3,902	3,006
Interest cost		5,139	6,042	5,598
Actuarial (gain)/loss		(2,808)	(2,589)
Benefits paid		(5,696)	(5,418)
Benefit obligation as of end of year		167,598	161,233	159,296
Fair value of plan assets as of beginning of year		52,173	44,853
Actual return on plan assets		7,371	7,320
Fair value of plan assets as of end of year		59,544	52,173	$ 44,853
Funded status		(108,054)	(109,060)
Other current liabilities		(684)	(669)
Non-current liabilities		(107,370)	(108,391)
Net amount recognized		(108,054)	(109,060)
Unrecognized prior service cost (credit)		(2,741)	(3,570)
Unrecognized net actuarial loss		48,872	53,737
Total		46,131	50,167
Less regulatory asset		(45,350)	(48,708)
Accumulated other comprehensive loss for unfunded benefit obligation for pensions and other postretirement benefit plans		$ 781	$ 1,459
Discount rate for benefit obligation		3.40%	3.27%
Discount rate for annual expense		3.27%	3.89%
Expected long-term return on plan assets		4.60%	5.30%
Other Postretirement Benefits [Member] | Pre-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend – initial		6.00%	6.25%
Medical cost trend – ultimate		5.00%	5.00%
Ultimate medical cost trend year		2026	2026
Other Postretirement Benefits [Member] | Post-Age 65 [Member]
Defined Benefit Plan Disclosure [Line Items]
Medical cost trend – initial		6.00%	6.25%
Medical cost trend – ultimate		5.00%	5.00%
Ultimate medical cost trend year		2026	2026
Other Postretirement Benefits [Member] | Retirees [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		$ 75,876
Benefit obligation as of end of year		78,347	$ 75,876
Other Postretirement Benefits [Member] | Fully eligible employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		32,097
Benefit obligation as of end of year		32,144	32,097
Other Postretirement Benefits [Member] | Other participants [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation as of beginning of year		53,260
Benefit obligation as of end of year		$ 57,107	$ 53,260
[1]	Total service costs in the table above are recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses.

Pension Plans and Other Postr_6

Pension Plans and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Plan And SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	$ 25,306	$ 22,392	$ 19,755
Interest cost		26,160	27,853	28,417
Expected return on plan assets		(39,088)	(34,886)	(31,763)
Amortization of prior service cost		257	257	257
Net loss recognition		6,645	6,717	10,216
Net periodic benefit cost		19,280	22,333	26,882
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	[1]	4,114	3,902	3,006
Interest cost		5,139	6,042	5,598
Expected return on plan assets		(2,400)	(2,377)	(2,101)
Amortization of prior service cost		(921)	(958)	(981)
Net loss recognition		3,865	4,871	4,013
Net periodic benefit cost		$ 9,797	$ 11,480	$ 9,535
[1]	Total service costs in the table above are recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses.

Pension Plans and Other Postr_7

Pension Plans and Other Postretirement Benefit Plans - Investment Allocation Percentages By Asset Classes (Details)	Dec. 31, 2021	Dec. 31, 2020
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	55.00%	35.00%
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	40.00%	49.00%
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	5.00%	7.00%
Absolute Return [Member]
Defined Benefit Plan Disclosure [Line Items]
Target investment allocation	0.00%	9.00%

Pension Plans and Other Postr_8

Pension Plans and Other Postretirement Benefit Plans - Schedule of Fair Value Hierarchy of pension Plan's Assets (Details) - Pension Plan And SERP [Member] - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 750,963	$ 722,024	$ 642,063
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		6,259	3,309
Fixed Income Securities [Member] | US Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		19,310	10,990
Fixed Income Securities [Member] | Domestic Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		233,496	279,857
Fixed Income Securities [Member] | Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		34,270	39,634
Fixed Income Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		18,558	22,431
Mutual Funds [Member] | U.S Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		236,552	146,375
Mutual Funds [Member] | International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		112,873	96,311
Mutual Funds [Member] | Absolute Return [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]		11,640
Common/Collective Trusts [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		31,040	29,532
Partnership And Closely Held Investments [Member] | International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		50,427	26,760
Partnership And Closely Held Investments [Member] | Absolute Return [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	363	47,188
Partnership And Closely Held Investments [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		7,815	7,997
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		349,425	254,326
Level 1 [Member] | Mutual Funds [Member] | U.S Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		236,552	146,375
Level 1 [Member] | Mutual Funds [Member] | International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		112,873	96,311
Level 1 [Member] | Mutual Funds [Member] | Absolute Return [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]		11,640
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		311,893	356,221
Level 2 [Member] | Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		6,259	3,309
Level 2 [Member] | Fixed Income Securities [Member] | US Government Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		19,310	10,990
Level 2 [Member] | Fixed Income Securities [Member] | Domestic Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		233,496	279,857
Level 2 [Member] | Fixed Income Securities [Member] | Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		34,270	39,634
Level 2 [Member] | Fixed Income Securities [Member] | Municipal Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 18,558	$ 22,431
[1]	This category invests in multiple strategies to diversify risk and reduce volatility. The strategies include: (a) event driven, relative value, convertible, and fixed income arbitrage, (b) distressed investments, (c) long/short equity and fixed income and (d) market neutral strategies.

Pension Plans and Other Postr_9

Pension Plans and Other Postretirement Benefit Plans - Schedule of Fair Value Hierarchy of Other Postretirement Plan Assets (Details) - Other Postretirement Benefits [Member] - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 59,544	$ 52,173	$ 44,853
Mutual Fund [Member] | Balanced Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	59,545	52,173
Level 1 [Member] | Mutual Fund [Member] | Balanced Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	$ 59,545	$ 52,173
[1]	The balanced index fund for 2021 and 2020 is a single mutual fund that includes a percentage of U.S. equity and fixed income securities and International equity and fixed income securities.

Pension Plans and Other Post_10

Pension Plans and Other Postretirement Benefit Plans - Employer Matching Contributions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits, Description [Abstract]
Employer 401(k) matching contributions	$ 11,671	$ 11,742	$ 10,412

Pension Plans and Other Post_11

Pension Plans and Other Postretirement Benefit Plans - Deferred Compensation Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred Compensation, Excluding Share-based Payments and Retirement Benefits [Member]
Deferred Compensation Arrangement With Individual Excluding Share Based Payments And Postretirement Benefits [Line Items]
Deferred compensation assets and liabilities	$ 9,513	$ 9,174

Accounting For Income Taxes - S

Accounting For Income Taxes - Schedule of Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Current income tax expense (benefit)	$ 807	$ (37,913)	$ 16,276
Deferred income tax expense	11,224	44,964	15,098
Total income tax expense	$ 12,031	$ 7,051	$ 31,374

Accounting For Income Taxes - A

Accounting For Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Components of Income Tax Expense (Benefit) [Line Items]
Federal statutory tax rate	21.00%	21.00%	21.00%	21.00%	35.00%
State Tax Credit Carryforward [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Tax credit carryforward, amount	$ 17.1
Tax credit carryforwards, net of valuation allowance	7.5
Tax credit carryforward, valuation allowance	$ (9.6)
Minimum [Member] | State Tax Credit Carryforward [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Tax credit carryforward, expiration date	2022
Maximum [Member] | State Tax Credit Carryforward [Member]
Components of Income Tax Expense (Benefit) [Line Items]
Tax credit carryforward, expiration date	2035

Accounting For Income Taxes -_2

Accounting For Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal income taxes at statutory rates	$ 33,467	$ 28,673	$ 47,909
Tax effect of regulatory treatment of utility plant differences	(13,820)	(12,893)	(9,967)
State income tax expense	1,385	814	1,465
Acquisition costs			(1,712)
Flow through related to deduction of meters and mixed service costs	(8,678)
Non-plant excess deferred turnaround		(8,476)	(5,690)
Tax loss on sale of METALfx			(1,272)
Customer refunds related to prior years at 35 percent		(1,189)
Other	(323)	122	641
Total income tax expense	$ 12,031	$ 7,051	$ 31,374
Federal statutory tax rate	21.00%	21.00%	21.00%	21.00%	35.00%
Tax effect of regulatory treatment of utility plant differences	(8.70%)	(9.40%)	(4.30%)
State income tax expense	0.80%	0.60%	0.60%
Acquisition costs			(0.70%)
Flow through related to deduction of meters and mixed service costs	(5.40%)
Non-plant excess deferred turnaround		(6.20%)	(2.50%)
Tax loss on sale of METALfx			(0.60%)
Customer refunds related to prior years at 35 percent		(0.90%)
Other	(0.20%)	0.10%	0.30%
Effective Income Tax Rate Reconciliation, Percent	7.50%	5.20%	13.80%

Accounting For Income Taxes -_3

Accounting For Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Parenthetical) (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Regulatory Liabilities [Line Items]
Federal statutory tax rate			21.00%	21.00%	21.00%	21.00%	35.00%
Regulatory liability, current			$ 77,149	$ 46,435
Effective income tax rate reconciliation, excess deferred income tax reversal amount				$ 8,476	$ 5,690
Washington Utilities and Transportation Commission [Member]
Regulatory Liabilities [Line Items]
Effective income tax rate reconciliation, excess deferred income tax reversal amount	$ 8,400
Washington Utilities and Transportation Commission [Member] | Income Tax Related [Member]
Regulatory Liabilities [Line Items]
Regulatory liability, current	$ 10,900
Idaho Public Utilities Commission [Member]
Regulatory Liabilities [Line Items]
Effective income tax rate reconciliation, excess deferred income tax reversal amount		$ 5,100
Idaho Public Utilities Commission [Member] | Income Tax Related [Member]
Regulatory Liabilities [Line Items]
Regulatory liability, current		$ 6,400

Accounting For Income Taxes -_4

Accounting For Income Taxes - Schedule of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred income tax assets:
Regulatory liabilities	$ 200,513	$ 179,871
Tax credits and NOL carryforwards	64,994	57,516
Provisions for pensions	25,650	37,501
Other	38,181	42,641
Total gross deferred income tax assets	329,338	317,529
Valuation allowances for deferred tax assets	(9,626)	(10,021)
Total deferred income tax assets after valuation allowances	319,712	307,508
Deferred income tax liabilities:
Utility property, plant, and equipment	688,856	666,639
Regulatory assets	264,978	232,697
Other	8,587	2,884
Total deferred income tax liabilities	962,421	902,220
Net long-term deferred income tax liability	$ 642,709	$ 594,712

Energy Purchase Contracts Addit

Energy Purchase Contracts Additional Information (Details)	12 Months Ended
	Dec. 31, 2021
Minimum [Member]
Energy Purchase Contracts [Line Items]
Remaining term of purchase contract	1 month
Maximum [Member]
Energy Purchase Contracts [Line Items]
Remaining term of purchase contract	25 years

Energy Purchase Contracts (Sche

Energy Purchase Contracts (Schedule Of Utility Total Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Energy Purchase Contracts [Abstract]
Utility power resources	$ 431,199	$ 324,297	$ 376,769

Energy Purchase Contracts (Futu

Energy Purchase Contracts (Future Contractual Commitments For Power Resources And Natural Gas Resources) (Details) $ in Thousands	Dec. 31, 2021USD ($)
Energy Purchase Contracts [Line Items]
2022	$ 285,280
2023	254,060
2024	243,274
2025	230,300
2026	216,324
Thereafter	2,271,019
Total	3,500,257
Power Resources [Member]
Energy Purchase Contracts [Line Items]
2022	198,052
2023	187,552
2024	200,693
2025	193,877
2026	184,230
Thereafter	1,888,038
Total	2,852,442
Natural Gas Resources [Member]
Energy Purchase Contracts [Line Items]
2022	87,228
2023	66,508
2024	42,581
2025	36,423
2026	32,094
Thereafter	382,981
Total	647,815
Generation Transmission And Distribution Facilities [Member]
Energy Purchase Contracts [Line Items]
2022	28,912
2023	29,680
2024	30,471
2025	31,287
2026	32,127
Thereafter	212,852
Total	$ 365,329

Energy Purchase Contracts (PUD

Energy Purchase Contracts (PUD Contracts Expenses) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)
P U D Contracts Expenses [Abstract]
Long-term contract for purchase of electric power, amount of long-term debt or lease obligation outstanding	$ 278.3

Committed Lines of Credit - Add

Committed Lines of Credit - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Apr. 30, 2014
Avista Utilities [Member]
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity				$ 400,000,000
Line of credit facility, expiration date	2026-06
Line of credit facility additional expiration period		1 year
Line of credit facility, covenant terms, maximum debt to equity ratio		65.00%
Average interest rate		1.11%	1.22%
Alaska Electric Light & Power [Member]
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity		$ 25,000,000
Line of credit facility, expiration date		2024-11
Line of credit facility, covenant terms, maximum debt to equity ratio		67.50%
Line of credit, outstanding		$ 0	$ 1,000,000
Average interest rate			1.65%

Committed Lines of Credit - Sch

Committed Lines of Credit - Schedule of Balances Outstanding and Interest Rates of Borrowings (Details) - Avista Utilities [Member] - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Balance outstanding at end of period	$ 284,000	$ 102,000
Letters of credit outstanding at end of period	$ 34,000	$ 27,618
Average interest rate at end of period	1.11%	1.22%

Credit Agreement - Additional I

Credit Agreement - Additional Information (Details) - Avista Utilities [Member] $ in Millions	1 Months Ended
	Apr. 30, 2020USD ($)
Short-term Debt [Line Items]
Maximum borrowing capacity credit agreement	$ 100
Credit agreement, expiration month and year	2021-04
Credit agreement amount borrowed	$ 100

Long-Term Debt - Schedule Of Lo

Long-Term Debt - Schedule Of Long-Term Debt Instruments (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Secured Debt		$ 2,232,200	$ 2,092,200
Secured and Unsecured Debt		2,247,200	2,107,200
Unamortized debt discount		(632)	(710)
Unamortized Debt Issuance Expense		(14,498)	(14,256)
Total		2,232,070	2,092,234
Current portion of long-term debt		(250,000)	0
Long-term debt		$ 1,898,370	2,008,534
First Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		8.00%
Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds		$ (83,700)	(83,700)
2032 | Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds		66,700
2034 | Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds		17,000
Avista Utilities [Member]
Debt Instrument [Line Items]
Secured Debt		$ 2,157,200	2,017,200
Avista Utilities [Member] | 2022 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2022
Debt Instrument, Interest Rate, Stated Percentage		5.13%
Secured Debt		$ 250,000	250,000
Avista Utilities [Member] | 2023 7.18% - 7.54% | Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year		2023
Medium-Term Notes, Noncurrent		$ 13,500	13,500
Avista Utilities [Member] | 2023 7.18% - 7.54% | Minimum [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.18%
Avista Utilities [Member] | 2023 7.18% - 7.54% | Maximum [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.54%
Avista Utilities [Member] | 2028 | Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year		2028
Debt Instrument, Interest Rate, Stated Percentage		6.37%
Medium-Term Notes, Noncurrent		$ 25,000	25,000
Avista Utilities [Member] | 2032 | Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year		2032
Pollution Control Bonds		$ 66,700	66,700
Avista Utilities [Member] | 2034 | Secured Debt [Member]
Debt Instrument [Line Items]
Maturity Year		2034
Pollution Control Bonds		$ 17,000	17,000
Avista Utilities [Member] | 2035 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2035
Debt Instrument, Interest Rate, Stated Percentage		6.25%
Secured Debt		$ 150,000	150,000
Avista Utilities [Member] | 2037 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2037
Debt Instrument, Interest Rate, Stated Percentage		5.70%
Secured Debt		$ 150,000	150,000
Avista Utilities [Member] | 2040 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2040
Debt Instrument, Interest Rate, Stated Percentage		5.55%
Secured Debt		$ 35,000	35,000
Avista Utilities [Member] | 2041 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2041
Debt Instrument, Interest Rate, Stated Percentage		4.45%
Secured Debt		$ 85,000	85,000
Avista Utilities [Member] | 2044 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2044
Debt Instrument, Interest Rate, Stated Percentage		4.11%
Secured Debt		$ 60,000	60,000
Avista Utilities [Member] | 2045 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2045
Debt Instrument, Interest Rate, Stated Percentage		4.37%
Secured Debt		$ 100,000	100,000
Avista Utilities [Member] | 2047 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2047
Debt Instrument, Interest Rate, Stated Percentage		4.23%
Secured Debt		$ 80,000	80,000
Avista Utilities [Member] | 2047 3.91% | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2047
Debt Instrument, Interest Rate, Stated Percentage		3.91%
Secured Debt		$ 90,000	90,000
Avista Utilities [Member] | 2048 4.35% | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2048
Debt Instrument, Interest Rate, Stated Percentage		4.35%
Secured Debt		$ 375,000	375,000
Avista Utilities [Member] | 2049 3.43% | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2049
Debt Instrument, Interest Rate, Stated Percentage		3.43%
Secured Debt		$ 180,000	180,000
Avista Utilities [Member] | 2050 3.07% | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2050
Debt Instrument, Interest Rate, Stated Percentage		3.07%
Secured Debt		$ 165,000	165,000
Avista Utilities [Member] | 2051 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2051
Debt Instrument, Interest Rate, Stated Percentage		3.54%
Secured Debt		$ 175,000	175,000
Avista Utilities [Member] | 2.90% Due in 2051 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year	2051	2051
Debt Instrument, Interest Rate, Stated Percentage	2.90%	2.90%
Secured Debt		$ 140,000
Alaska Electric Light & Power [Member] | 2044 | First Mortgage [Member]
Debt Instrument [Line Items]
Maturity Year		2044
Debt Instrument, Interest Rate, Stated Percentage		4.54%
Secured Debt		$ 75,000	75,000
Alaska Energy Resources Company [Member] | 2024 | Unsecured Debt [Member]
Debt Instrument [Line Items]
Maturity Year		2024
Debt Instrument, Interest Rate, Stated Percentage		3.44%
Unsecured Debt		$ 15,000	$ 15,000

Long-Term Debt - Schedule Of _2

Long-Term Debt - Schedule Of Long-Term Debt Instruments (Parenthetical) (Details)	1 Months Ended		12 Months Ended
	Dec. 31, 2021USD ($)	Sep. 30, 2021USD ($)	Dec. 31, 2021USD ($)Contract	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Apr. 30, 2014USD ($)
Debt Instrument [Line Items]
Secured Debt	$ 2,232,200,000		$ 2,232,200,000	$ 2,092,200,000
Proceeds from issuance of long-term debt			140,000,000	165,000,000	$ 180,000,000
Avista Utilities [Member]
Debt Instrument [Line Items]
Secured Debt	$ 2,157,200,000		$ 2,157,200,000	2,017,200,000
Line of credit facility, maximum borrowing capacity						$ 400,000,000
First Mortgage [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%		8.00%
2032 | Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	$ 66,700,000		$ 66,700,000
2032 | Secured Debt [Member] | Avista Utilities [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	66,700,000		$ 66,700,000	66,700,000
Maturity Year			2032
2034 | Secured Debt [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	17,000,000		$ 17,000,000
2034 | Secured Debt [Member] | Avista Utilities [Member]
Debt Instrument [Line Items]
Pollution Control Bonds	17,000,000		$ 17,000,000	17,000,000
Maturity Year			2034
2.90% Due in 2051 [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	400,000,000		$ 400,000,000
2.90% Due in 2051 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt	70,000,000
2.90% Due in 2051 [Member] | First Mortgage [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Number of interest rate swaps settled | Contract			4
Notional Amount	45,000,000		$ 45,000,000
Net payments from settlement of derivatives			17,200,000
2.90% Due in 2051 [Member] | First Mortgage [Member] | Avista Utilities [Member]
Debt Instrument [Line Items]
Secured Debt	$ 140,000,000		$ 140,000,000
Proceeds from issuance of long-term debt		$ 70,000,000
Debt Instrument, Interest Rate, Stated Percentage	2.90%	2.90%	2.90%
Maturity Year		2051	2051
2050 3.07% | First Mortgage [Member] | Avista Utilities [Member]
Debt Instrument [Line Items]
Secured Debt	$ 165,000,000		$ 165,000,000	$ 165,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.07%		3.07%
Maturity Year			2050

Long-Term Debt - Schedule Of _3

Long-Term Debt - Schedule Of Long-Term Debt Maturities (Details) - Future Long Term Debt Maturities Including Long Term Debt To Affiliated Trusts [Member] $ in Thousands	Dec. 31, 2021USD ($)
Debt Instrument [Line Items]
2022	$ 250,000
2023	13,500
2024	15,000
Thereafter	1,936,547
Total	$ 2,215,047

Long-Term Debt- Additional Info

Long-Term Debt- Additional Information (Details) - First Mortgage [Member] $ in Millions	Dec. 31, 2021USD ($)
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Avista Utilities [Member]
Debt Instrument [Line Items]
Amount of First Mortgage Bonds that Could be Issued, Percent	66.66%
Amount of First Mortgage Bonds that Could be Issued	$ 1,800
Alaska Electric Light & Power [Member]
Debt Instrument [Line Items]
Amount of First Mortgage Bonds that Could be Issued, Percent	66.66%
Amount of First Mortgage Bonds that Could be Issued	$ 38.2

Long- Term Debt to Affiliated_3

Long- Term Debt to Affiliated Trust - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2000
Debt Instrument [Line Items]
Payments for repurchase of trust preferred securities		$ 10
Avista Corp [Member]
Debt Instrument [Line Items]
Noncontrolling interest, ownership percentage by parent	100.00%
1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] | Avista Capital II [Member]
Debt Instrument [Line Items]
Junior subordinated debenture issuance date	1997
Principal amount	$ 51.5
Trust Preferred Securities Subject to Mandatory Redemption [Member] | 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] | Avista Capital II [Member]
Debt Instrument [Line Items]
Principal amount	$ 50
Debt instrument, description of variable rate basis	LIBOR
Debt instrument, basis spread on variable rate	0.875%
Common Trust Securities [Member] | 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] | Avista Capital II [Member]
Debt Instrument [Line Items]
Principal amount	$ 1.5

Long-Term Debt to Affiliated Tr

Long-Term Debt to Affiliated Trust - Schedule of Distribution Rates Paid (Details) - Trust Preferred Securities Subject to Mandatory Redemption [Member]	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Interest rate	1.05%	1.10%	2.79%
Minimum [Member]
Debt Instrument [Line Items]
Interest rate	0.99%	1.10%	2.79%
Maximum [Member]
Debt Instrument [Line Items]
Interest rate	1.10%	2.79%	3.61%

Fair Value - Schedule of Carryi

Fair Value - Schedule of Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease Obligation	$ 48,815	$ 51,750
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 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,157,651	1,189,824
Level 3 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,200,000	1,060,000
Level 3 [Member] | Reported Value Measurement [Member] | Alaska Electric Light & Power [Member] | Finance Lease [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease Obligation	48,815	51,750
Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,366,619	1,235,248
Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Alaska Electric Light & Power [Member] | Finance Lease [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease Obligation	54,000	58,700
Affiliated Entity [Member] | Level 3 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	51,547	51,547
Affiliated Entity [Member] | Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 43,299	$ 43,815

Fair Value - Additional Informa

Fair Value - Additional Information (Details) $ in Thousands	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 22,168	$ 14,196
Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 100	$ 500
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	100
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	84
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	140.27

Fair Value - Schedule of Fair V

Fair Value - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		$ 36,581	$ 24,702
Liability		74,940	83,280
Fair Value, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		13,460	10,222
Financial Liabilities Fair Value Disclosure		33,327	51,435
Counterparty and Cash Collateral Netting, Assets		(32,524)	(23,179)
Counterparty and Cash Collateral Netting, Liabilities		(41,613)	(31,845)
Fair Value, Recurring [Member] | Fixed Income Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	[1]	1,809	2,471
Fair Value, Recurring [Member] | Equity Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	[1]	7,594	6,228
Fair Value, Recurring [Member] | Energy commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and Cash Collateral Netting, Assets		(40,300)	(22,152)
Derivative Asset		1,433	1,493
Counterparty and Cash Collateral Netting, Liabilities		(31,211)	(22,768)
Derivative Liability		2,908	262
Fair Value, Recurring [Member] | Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and Cash Collateral Netting, Assets		(143)	(75)
Counterparty and Cash Collateral Netting, Liabilities		(143)	(75)
Derivative Liability		7,771	8,410
Fair Value, Recurring [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		19	30
Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and Cash Collateral Netting, Assets		(1,170)	(952)
Derivative Asset		1,149
Counterparty and Cash Collateral Netting, Liabilities		(1,170)	(9,002)
Derivative Liability		24,104	42,763
Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		9,403	8,699
Fair Value, Recurring [Member] | Level 1 [Member] | Fixed Income Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	[1]	1,809	2,471
Fair Value, Recurring [Member] | Level 1 [Member] | Equity Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	[1]	7,594	6,228
Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		36,438	24,627
Financial Liabilities Fair Value Disclosure		67,026	74,795
Fair Value, Recurring [Member] | Level 2 [Member] | Energy commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		41,733	23,645
Liability		34,119	23,030
Fair Value, Recurring [Member] | Level 2 [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		19	30
Fair Value, Recurring [Member] | Level 2 [Member] | Interest Rate Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		2,319	952
Liability		25,274	51,765
Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		143	75
Financial Liabilities Fair Value Disclosure		7,914	8,485
Fair Value, Recurring [Member] | Level 3 [Member] | Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		143	75
Liability		$ 7,914	$ 8,485
[1]	These assets are included in other property and investments-net and other non-current assets on the Consolidated Balance Sheets

Fair Value - Schedule of Quanti

Fair Value - Schedule of Quantitative Information (Details) - Natural Gas Exchange Agreements [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)MMBTU$ / MMBTU	Dec. 31, 2020USD ($)
Purchase [Member] | Minimum [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative, Forward Price	2.35
Transaction/Delivery Volumes | MMBTU	130,000
Purchase [Member] | Maximum [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative, Forward Price	4.08
Transaction/Delivery Volumes | MMBTU	310,000
Purchase [Member] | Weighted Average [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative, Forward Price	2.96
Sales [Member] | Minimum [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative, Forward Price	2.38
Transaction/Delivery Volumes | MMBTU	25,000
Sales [Member] | Maximum [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative, Forward Price	9.50
Transaction/Delivery Volumes | MMBTU	310,000
Sales [Member] | Weighted Average [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative, Forward Price	4.51
Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative Liability | $	$ (7,771)	$ (8,410)

Fair Value - Schedule of Activi

Fair Value - Schedule of Activity For Energy Commodity Derivative Assets (Liabilities) Measured At Fair Value Using Significant Unobservable Inputs (Level 3) (Details) - Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (8,410)	$ (2,976)	$ (5,262)
Included in regulatory assets	4,292	(4,311)	8,610
Settlements	(3,653)	(1,123)	(6,324)
Ending Balance	(7,771)	(8,410)	(2,976)
Natural Gas Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(8,410)	(2,976)	(2,774)
Included in regulatory assets	4,292	(4,311)	8,175
Settlements	(3,653)	(1,123)	(8,377)
Ending Balance	$ (7,771)	$ (8,410)	(2,976)
Power Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance			(2,488)
Included in regulatory assets			435
Settlements			$ 2,053

Fair Value - Schedules of Nonre

Fair Value - Schedules of Nonrecurring Fair Value Measurements (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Carrying Value	[1]	$ 24,161	$ 15,110
Gains (losses)		$ 8,761	$ 925
[1]	Carrying value is adjusted to fair value as of the measurement date when observable changes in fair value occur, such as a transaction involving the underlying asset. These assets are measured using a market approach and are level 2 assets.

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Preferred stock, shares outstanding	0	0
Amount available for dividend distribution without affecting covenants	$ 322,300
Preferred stock, shares authorized	10,000,000
Proceeds from issuance of common stock	$ 89,998	$ 72,200	$ 64,573
Common stock, shares authorized	200,000,000	200,000,000
Common Stock [Member]
Class Of Stock [Line Items]
Shares issued through sales agency agreements	2,150,336	1,905,000	1,409,588
Issuance of common stock through sales agency agreements, net of issuance costs	$ 88,457	$ 70,561	$ 63,571
Sales Agency Agreement [Member]
Class Of Stock [Line Items]
Common stock, shares authorized	4,300,000
Common stock shares authorized under sales agency agreements remaining shares authorized to sell	2,100,000
Avista Utilities [Member]
Class Of Stock [Line Items]
Regulatory restrictions, maximum debt to equity	35.00%

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Loss [Abstract]
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $3,822 and $3,822, respectively	$ 11,039	$ 14,378

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss, Net of Tax (Parenthetical) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Loss [Abstract]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans net unamortized (gain) loss, tax	$ 2,934	$ 3,822

Accumulated Other Comprehensi_5

Accumulated Other Comprehensive Loss - Reclassification out of Accumulated Other Comprehensive Income (Details) - Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net prior service cost	$ (793)	$ (794)	$ (794)
Amortization of net loss	38,070	5,586	17,074
Adjustment due to effects of regulation	(33,050)	(10,006)	(19,309)
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, before tax	4,227	(5,214)	(3,029)
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, tax	(888)	1,095	636
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, after tax	$ 3,339	$ (4,119)	$ (2,393)

Earnings Per Common Share Att_3

Earnings Per Common Share Attributable to Avista Corporation Shareholders - Schedule of Computation of Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income attributable to Avista Corp. shareholders	$ 147,334	$ 129,488	$ 196,979
Denominator:
Weighted-average number of common shares outstanding-basic	69,951	67,962	66,205
Effect of dilutive securities:
Performance and restricted stock awards	134	140	124
Weighted-average number of common shares outstanding-diluted	70,085	68,102	66,329
Earnings per common share attributable to Avista Corp. shareholders:
Basic	$ 2.11	$ 1.91	$ 2.98
Diluted	$ 2.10	$ 1.90	$ 2.97

Earnings Per Common Share Att_4

Earnings Per Common Share Attributable to Avista Corporation Shareholders - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share, amount	0	0	0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	1 Months Ended		12 Months Ended
	Jul. 31, 2021USD ($)	Aug. 31, 2019USD ($)	Dec. 31, 2021	May 14, 2021aBuilding	Sep. 02, 2020aBuilding
Loss Contingencies [Line Items]
Owners percentage interest			15.00%
Natural and Cultural Damage Claim [Member]
Loss Contingencies [Line Items]
Litigation settlement damages claim amount	$ 2,000,000
Boyds Fire [Member] | Damage from Fire [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value		$ 4,400,000
Labor Day Windstorm [Member] | Damage from Fire [Member]
Loss Contingencies [Line Items]
Wildfire covered area | a					22,000
Number of residential, commercial and other structures impacted | Building					230
Babb Road Fire [Member] | Damage from Fire [Member]
Loss Contingencies [Line Items]
Number of residential, commercial and other structures impacted | Building				220
Road fire covered area | a				15,000
System Unit Resource Protection Act [Member] | Natural and Cultural Damage Claim [Member]
Loss Contingencies [Line Items]
Increased potential claim	$ 6,000,000
Colstrip [Member]
Loss Contingencies [Line Items]
Agreement voting requirement			These business disagreements, in turn, have led to disagreements as to the interpretation of the O&O Agreement, including, but not limited to, what percentage voting requirement under the O&O Agreement (55 percent vs. 100 percent) is needed to remove one or more of the Colstrip units from service or to make a determination that the project can no longer be operated consistent with prudent utility practice or the requirements of governmental agencies having jurisdiction.
Avista Corp [Member]
Loss Contingencies [Line Items]
Percentage of maximum ownership			30.00%
Avista Corp [Member] | Colstrip [Member]
Loss Contingencies [Line Items]
Owners percentage interest			15.00%
Avista Utilities [Member]
Loss Contingencies [Line Items]
Percentage Of Employees, Collective Bargaining Agreement			40.00%
Majority Of Bargaining Unit Employees, Percentage			90.00%

Regulatory Matters - Schedule o

Regulatory Matters - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Regulated Asset Liability [Line Items]
Earning a return, asset	$ 652,603
Not earning a return, asset	193,618
Pending regulatory treatment, asset	58,188
Regulatory assets	43,783	$ 13,673
Non-current regulatory assets	860,626	750,443
Earning a return, liability	738,730
Not earning a return, liability	42,099
Pending Regulatory Treatment Liability	157,835
Regulatory liabilities	77,149	46,435
Non-current regulatory liabilities	861,515	784,820
Natural Gas Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	0	874
Non-current regulatory liabilities	0	0
Deferred Power Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	11,891
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	6,457	20,299
Non-current regulatory liabilities	5,434	17,570
Utility Plant Retirement Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	350,190
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	0	0
Non-current regulatory liabilities	350,190	325,832
Income Tax Related Liabilities [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	346,847
Not earning a return, liability	24,411
Pending Regulatory Treatment Liability	143,862
Regulatory liabilities	56,331	14,952
Non-current regulatory liabilities	458,789	399,677
Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	13,589
Not earning a return, liability	0
Pending Regulatory Treatment Liability	1,473
Regulatory liabilities	0	0
Non-current regulatory liabilities	$ 15,062	15,046
Decoupling Rebates [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory liability	1 year
Earning a return, liability	$ 9,308
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	3,049	1,447
Non-current regulatory liabilities	6,259	1,519
COVID-19 Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	0
Pending Regulatory Treatment Liability	12,500
Regulatory liabilities	0	0
Non-current regulatory liabilities	12,500	10,949
Other Regulatory Liabilities [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	6,905
Not earning a return, liability	17,688
Pending Regulatory Treatment Liability	0
Regulatory liabilities	11,312	8,863
Non-current regulatory liabilities	13,281	14,227
Deferred Income Tax [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	244,154
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	244,154	108,517
Pension and Other Postretirement Benefit Plans [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	165,696
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	165,696	198,746
Energy commodity derivatives
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	15,385
Pending regulatory treatment, asset	0
Regulatory assets	12,447	2,073
Non-current regulatory assets	2,938	5,722
Unamortized Debt Repurchase Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	6,768
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	$ 6,768	7,512
Settlement with Coeur d'Alene Tribe [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	38 years
Earning a return, asset	$ 38,926
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	38,926	40,043
Demand Side Management Programs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	3,974
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	$ 3,974	3,814
Decoupling Surcharge [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	2 years
Earning a return, asset	$ 24,532
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	9,907	7,123
Non-current regulatory assets	14,625	17,123
Utility Plant to be Abandoned [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	26,771
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	26,771	28,916
Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	158,082
Not earning a return, asset	0
Pending regulatory treatment, asset	41,672
Regulatory assets	0	0
Non-current regulatory assets	199,754	214,851
Deferred power costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	10,835
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	7,334	1,775
Non-current regulatory assets	3,501	1,562
Deferred Natural Gas Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	21,027
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	14,095	2,308
Non-current regulatory assets	6,932	0
AFUDC Above FERC Allowed Rate [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	48,455
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	48,455	47,393
COVID-19 Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	0
Pending regulatory treatment, asset	13,591
Regulatory assets	0	0
Non-current regulatory assets	13,591	8,166
Advanced Meter Infrastructure [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	36,008
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	36,008	26,379
Other Regulatory Assets [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	37,045
Not earning a return, asset	8,563
Pending regulatory treatment, asset	2,925
Regulatory assets	0	394
Non-current regulatory assets	$ 48,533	$ 41,699

Regulatory Matters - Schedule_2

Regulatory Matters - Schedule of Regulatory Assets and Liabilities (Parenthetical) (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Regulated Asset Liability [Line Items]
Federal statutory tax rate	21.00%	21.00%	21.00%	21.00%	35.00%
Avista Utilities [Member]
Regulated Asset Liability [Line Items]
Tax cuts and jobs act period to return plant related excess deferred income taxes	32 years
Alaska Electric Light & Power [Member]
Regulated Asset Liability [Line Items]
Tax cuts and jobs act period to return plant related excess deferred income taxes	40 years

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Regulated Asset Liability [Line Items]
Threshold limit of deadband and sharing bands for future surcharge or rebate to customer	$ 4,000,000
Company share of benefit (expense) under washington energy recovery mechanism	(7,700,000)	$ 6,200,000
Threshold to return washington energy recovery mechanism dollars to customers	$ 30,000,000
Proposed cumulative rebate refund period	2 years
Deferred natural gas costs, asset	$ 21,000,000	1,400,000
WASHINGTON
Regulated Asset Liability [Line Items]
Decoupling maximum rate increase request	3.00%
IDAHO | Power Deferrals Regulatory Asset [Member]
Regulated Asset Liability [Line Items]
Regulatory assets	$ 10,800,000	2,500,000
Power Deferrals Regulatory Liability [Member] | WASHINGTON
Regulated Asset Liability [Line Items]
Regulatory liabilities	11,900,000	37,900,000
Revenue Subject to Refund [Member] | WASHINGTON
Regulated Asset Liability [Line Items]
Regulatory liabilities	0	0
Revenue Subject to Refund [Member] | IDAHO
Regulated Asset Liability [Line Items]
Regulatory liabilities	686,000	686,000
Revenue Subject to Refund [Member] | OREGON
Regulated Asset Liability [Line Items]
Regulatory liabilities	$ 0	$ 0

Regulatory Matters - Schedule_3

Regulatory Matters - Schedule of Decoupling and Earnings Sharing Mechanisms (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
WASHINGTON | Decoupling Surcharge (Rebate) [Member]
Scheduleof Decouplingand Earnings Sharing [Line Items]
Regulatory assets	$ 13,522,000	$ 21,340,000
WASHINGTON | Revenue Subject to Refund [Member]
Scheduleof Decouplingand Earnings Sharing [Line Items]
Regulatory Liabilities	0	0
IDAHO | Decoupling Surcharge (Rebate) [Member]
Scheduleof Decouplingand Earnings Sharing [Line Items]
Regulatory assets		1,202,000
IDAHO | Revenue Subject to Refund [Member]
Scheduleof Decouplingand Earnings Sharing [Line Items]
Regulatory Liabilities	(686,000)	(686,000)
IDAHO | Decoupling Surcharge (Rebate) [Member]
Scheduleof Decouplingand Earnings Sharing [Line Items]
Regulatory Liabilities	(1,450,000)
OREGON | Revenue Subject to Refund [Member]
Scheduleof Decouplingand Earnings Sharing [Line Items]
Regulatory Liabilities	0	0
OREGON | Decoupling Surcharge (Rebate) [Member]
Scheduleof Decouplingand Earnings Sharing [Line Items]
Regulatory Liabilities	$ (3,152,000)	$ (1,262,000)

Information by Business Segme_3

Information by Business Segments (Additional Information) (Details)	12 Months Ended
	Dec. 31, 2021ReportableSegments
Segment Reporting [Abstract]
Number of reportable segments	2

Information by Business Segme_4

Information by Business Segments - Schedule of Business Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Operating revenues	$ 1,438,936	$ 1,321,891	$ 1,345,622
Resource costs	497,123	398,509	439,817
Other operating expenses	372,052	359,958	383,770
Depreciation and amortization	232,176	224,223	205,994
Income (loss) from operations	228,232	232,700	210,389
Interest expense	106,152	105,061	104,354
Income taxes	12,031	7,051	31,374
Net income (loss) from continuing operations attributable to Avista Corp. shareholders	147,334	129,488	196,979
Capital expenditures	441,209	405,674	443,345
Total Assets	6,853,583	6,402,097	6,082,456
Avista Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,392,999	1,277,468	1,295,873
Alaska Electric Light & Power [Member]
Segment Reporting Information [Line Items]
Operating revenues	45,366	42,809	37,265
Operating Segments [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,438,365	1,320,277	1,333,138
Resource costs	497,123	398,509	439,817
Other operating expenses	366,125	354,614	364,887
Depreciation and amortization	231,915	223,507	205,365
Income (loss) from operations	233,849	237,146	217,417
Interest expense	105,725	104,723	104,251
Income taxes	8,792	7,932	31,179
Net income (loss) from continuing operations attributable to Avista Corp. shareholders	132,782	132,905	191,435
Capital expenditures	439,939	404,306	442,510
Total Assets	6,723,666	6,304,311	5,984,661
Operating Segments [Member] | Avista Utilities [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,392,999	1,277,468	1,295,873
Resource costs	493,289	396,543	442,471
Other operating expenses	352,241	341,709	352,170
Depreciation and amortization	221,552	213,701	195,697
Income (loss) from operations	217,663	220,058	200,994
Interest expense	99,629	98,451	97,866
Income taxes	6,029	4,921	28,363
Net income (loss) from continuing operations attributable to Avista Corp. shareholders	125,558	124,810	183,977
Capital expenditures	435,887	397,292	434,077
Total Assets	6,458,244	6,035,340	5,713,268
Operating Segments [Member] | Alaska Electric Light & Power [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	45,366	42,809	37,265
Resource costs	3,834	(1,966)	2,654
Other operating expenses	13,884	12,905	12,717
Depreciation and amortization	10,363	9,806	9,668
Income (loss) from operations	16,186	17,088	16,423
Interest expense	6,096	6,272	6,385
Income taxes	2,763	3,011	2,816
Net income (loss) from continuing operations attributable to Avista Corp. shareholders	7,224	8,095	7,458
Capital expenditures	4,052	7,014	8,433
Total Assets	265,422	268,971	271,393
Other [Member] | Non-Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	571	1,614	12,484
Resource costs	0	0	0
Other operating expenses	5,927	5,344	18,883
Depreciation and amortization	261	716	629
Income (loss) from operations	(5,617)	(4,446)	(7,028)
Interest expense	522	524	1,032
Income taxes	3,239	881	(195)
Net income (loss) from continuing operations attributable to Avista Corp. shareholders	14,552	(3,417)	(5,544)
Capital expenditures	1,270	1,368	835
Total Assets	132,158	109,658	113,390
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0
Resource costs	0	0	0
Other operating expenses	0	0	0
Depreciation and amortization	0	0	0
Income (loss) from operations	0	0	0
Interest expense	(95)	(186)	(929)
Income taxes	0	0	0
Net income (loss) from continuing operations attributable to Avista Corp. shareholders	0	0	0
Capital expenditures	0	0	0
Total Assets	$ (2,241)	$ (11,872)	$ (15,595)

Termination of Proposed Acqui_2

Termination of Proposed Acquisition by Hydro One - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2019
Business Acquisition [Line Items]
Merger termination fee		$ 103,000
Merger transaction costs		$ 19,675
Hydro One [Member]
Business Acquisition [Line Items]
Merger termination fee	$ 103,000

Sale of METALfx- Additional Inf

Sale of METALfx- Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Apr. 30, 2019
METALfx [Member]
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		$ 16.5
Disposal group not discontinued operation gain (loss) on disposal net of tax	$ 3.3