Avista (AVA) 10-Q 31 Oct 23 2023 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2023	Oct. 27, 2023
Cover [Abstract]
Entity Registrant Name	AVISTA CORPORATION
Amendment Flag	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Information, Former Legal or Registered Name	None
City Area Code	509
Entity Incorporation, State or Country Code	WA
Document Transition Report	false
Document Quarterly Report	true
Document Type	10-Q
Document Period End Date	Sep. 30, 2023
Entity File Number	1-3701
Entity Tax Identification Number	91-0462470
Entity Address, Address Line One	1411 East Mission Avenue
Entity Address, City or Town	Spokane
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	99202-2600
Local Phone Number	489-0500
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Entity Central Index Key	0000104918
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		77,367,612
Title of 12(b) Security	Common Stock
Trading Symbol	AVA
Security Exchange Name	NYSE

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Utility revenues:
Utility revenues, exclusive of alternative revenue programs	$ 375,946	$ 365,142	$ 1,243,774	$ 1,228,059
Alternative revenue programs	3,578	(5,850)	(9,947)	(28,420)
Total utility revenues	379,524	359,292	1,233,827	1,199,639
Non-utility revenues	102	154	367	419
Total operating revenues	379,626	359,446	1,234,194	1,200,058
Utility operating expenses:
Resource costs	148,282	147,784	482,454	492,049
Other operating expenses	102,469	101,701	310,518	300,710
Depreciation and amortization	66,860	63,484	198,196	188,867
Taxes other than income taxes	23,280	26,002	82,091	86,777
Non-utility operating expenses	648	1,073	2,439	5,001
Total operating expenses	341,539	340,044	1,075,698	1,073,404
Income from operations	38,087	19,402	158,496	126,654
Capitalized interest	(926)	(828)	(2,634)	(2,853)
Other income-net	(7,401)	(3,964)	(16,456)	(22,749)
Income (loss) before income taxes	10,930	(5,641)	70,821	65,542
Income tax expense (benefit)	(3,786)	157	(16,224)	(11,678)
Net income (loss)	$ 14,716	$ (5,798)	$ 87,045	$ 77,220
Weighted-average common shares outstanding (thousands), basic	76,734	73,229	75,962	72,547
Weighted-average common shares outstanding (thousands), diluted	76,761	73,298	76,056	72,629
Earnings (loss) per common share:
Basic	$ 0.19	$ (0.08)	$ 1.15	$ 1.06
Diluted	$ 0.19	$ (0.08)	$ 1.14	$ 1.06
Non Affiliated Trusts [Member]
Utility operating expenses:
Interest expense	$ 34,827	$ 29,533	$ 104,929	$ 86,118
Affiliated Trusts [Member]
Utility operating expenses:
Interest expense	$ 657	$ 302	$ 1,836	$ 596

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 14,716	$ (5,798)	$ 87,045	$ 77,220
Other Comprehensive Income (Loss):
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes of ($5), $72, ($10) and $146, respectively	(19)	272	(56)	821
Total other comprehensive income (loss)	(19)	272	(56)	821
Comprehensive income (loss)	$ 14,697	$ (5,526)	$ 86,989	$ 78,041

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Other Comprehensive Income (Loss), Defined Benefit Plan, after Reclassification Adjustment, Tax	$ (5)	$ 72	$ (15)	$ 218

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current Assets:
Cash and cash equivalents	$ 8,630	$ 13,428
Accounts and notes receivable-less allowances of $3,900 and $6,473, respectively	131,900	255,746
Inventory	145,174	107,674
Regulatory assets	167,927	193,787
Other current assets	93,589	151,167
Total current assets	547,220	721,802
Net utility property	5,625,068	5,444,709
Goodwill	52,426	52,426
Non-current regulatory assets	855,099	833,328
Other property and investments-net and other non-current assets	390,217	365,085
Total assets	7,470,030	7,417,350
Current Liabilities:
Accounts payable	105,320	202,954
Current portion of long-term debt		13,500
Short-term borrowings	221,500	463,000
Regulatory liabilities	73,843	95,665
Other current liabilities	182,801	189,415
Total current liabilities	583,464	964,534
Pensions and other postretirement benefits	92,228	93,901
Deferred income taxes	726,265	674,995
Non-current regulatory liabilities	863,717	840,837
Other non-current liabilities and deferred credits	212,706	175,855
Total liabilities	5,060,143	5,082,682
Commitments and Contingencies (See Notes to Condensed Consolidated Financial Statements)
Shareholders' Equity:
Common stock, no par value; 200,000,000 shares authorized; 77,364,125 and 74,945,948 shares issued and outstanding, respectively	1,618,780	1,525,185
Accumulated other comprehensive loss	(2,114)	(2,058)
Retained earnings	793,221	811,541
Total shareholders’ equity	2,409,887	2,334,668
Total liabilities and equity	7,470,030	7,417,350
Non Affiliated Trusts [Member]
Current Liabilities:
Long-term debt	2,530,216	2,281,013
Affiliated Trusts [Member]
Current Liabilities:
Long-term debt	$ 51,547	$ 51,547

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Accounts and notes receivable, allowances	$ 3,900	$ 6,473
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares, issued	77,364,125	74,945,948
Common stock, shares outstanding	77,364,125	74,945,948

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Operating Activities:
Net income	$ 87,045	$ 77,220
Non-cash items included in net income:
Depreciation and amortization	198,272	188,961
Deferred income tax provision	(15,958)	(19,494)
Power and natural gas cost deferrals, net	(25,046)	(20,675)
Amortization of debt expense	2,431	1,506
Stock-based compensation expense	7,098	6,787
Equity-related AFUDC	(4,921)	(5,117)
Pension and other postretirement benefit expense	9,923	15,460
Other regulatory assets and liabilities	(12,582)	7,934
Other deferred debits and credits	31,058	(4,349)
Change in decoupling regulatory deferral	11,231	28,455
Realized and unrealized loss (gain) on assets and investments	966	(13,783)
Other	(2,525)	4,364
Contributions to defined benefit pension plan	(10,000)	(42,000)
Cash paid for settlement of interest rate swap agreements	(409)	(17,035)
Cash received for settlement of interest rate swap agreements	7,869
Changes in certain current assets and liabilities:
Accounts and notes receivable	119,908	32,347
Inventory	(37,500)	(38,714)
Collateral posted for derivative instruments	144,163	(29,362)
Income taxes receivable	(1,417)	5,991
Other current assets	(22,941)	4,074
Accounts payable	(96,794)	(22,145)
Other current liabilities	3,435	49,987
Net cash provided by operating activities	393,306	210,412
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(359,277)	(331,309)
Equity and property investments	(12,000)	(9,061)
Proceeds from sale of investments	3,200	1,000
Other	(503)	(941)
Net cash used in investing activities	(368,580)	(340,311)
Financing Activities:
Net decrease in short-term borrowings	(241,500)	(16,000)
Proceeds from issuance of long-term debt	250,000	399,856
Maturity of long-term debt and finance leases	(15,926)	(252,314)
Issuance of common stock, net of issuance costs	88,165	92,966
Cash dividends paid	(105,163)	(96,278)
Other	(5,100)	(6,136)
Net cash provided by (used in) financing activities	(29,524)	122,094
Net decrease in cash and cash equivalents	(4,798)	(7,805)
Cash and cash equivalents at beginning of period	13,428	22,168
Cash and cash equivalents at end of period	$ 8,630	$ 14,363

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]
Beginning Balance (in shares) at Dec. 31, 2021		71,497,523
Shares issued		2,277,281
Ending Balance (in shares) at Sep. 30, 2022		73,774,804
Beginning Balance at Dec. 31, 2021		$ 1,380,152	$ (11,039)	$ 785,631
Equity compensation expense		6,787
Issuance of common stock, net of issuance costs		92,966
Payment of minimum tax withholdings for share-based payment awards		(1,462)
Other comprehensive income (loss)	$ 821		821
Net income (loss)	77,220			77,220
Dividends on common stock				(96,227)
Ending Balance at Sep. 30, 2022	$ 2,234,849	$ 1,478,443	(10,218)	766,624
Dividends declared per common share	$ 1.32
Beginning Balance (in shares) at Jun. 30, 2022		72,976,082
Shares issued		798,722
Ending Balance (in shares) at Sep. 30, 2022		73,774,804
Beginning Balance at Jun. 30, 2022		$ 1,443,102	(10,490)	804,882
Equity compensation expense		3,140
Issuance of common stock, net of issuance costs		32,201
Other comprehensive income (loss)	$ 272		272
Net income (loss)	(5,798)			(5,798)
Dividends on common stock				(32,460)
Ending Balance at Sep. 30, 2022	$ 2,234,849	$ 1,478,443	(10,218)	766,624
Dividends declared per common share	$ 0.44
Beginning Balance (in shares) at Dec. 31, 2022	74,945,948	74,945,948
Shares issued		2,418,177
Ending Balance (in shares) at Sep. 30, 2023	77,364,125	77,364,125
Beginning Balance at Dec. 31, 2022	$ 2,334,668	$ 1,525,185	(2,058)	811,541
Equity compensation expense		7,097
Issuance of common stock, net of issuance costs		88,165
Payment of minimum tax withholdings for share-based payment awards		(1,667)
Other comprehensive income (loss)	(56)		(56)
Net income (loss)	87,045			87,045
Dividends on common stock				(105,365)
Ending Balance at Sep. 30, 2023	$ 2,409,887	$ 1,618,780	(2,114)	793,221
Dividends declared per common share	$ 1.38
Beginning Balance (in shares) at Jun. 30, 2023		76,524,184
Shares issued		839,941
Ending Balance (in shares) at Sep. 30, 2023	77,364,125	77,364,125
Beginning Balance at Jun. 30, 2023		$ 1,588,503	(2,095)	814,013
Equity compensation expense		1,637
Issuance of common stock, net of issuance costs		28,640
Other comprehensive income (loss)	$ (19)		(19)
Net income (loss)	14,716			14,716
Dividends on common stock				(35,508)
Ending Balance at Sep. 30, 2023	$ 2,409,887	$ 1,618,780	$ (2,114)	$ 793,221
Dividends declared per common share	$ 0.46

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ 14,716	$ (5,798)	$ 87,045	$ 77,220

Insider Trading Arrangements

Insider Trading Arrangements	9 Months Ended
	Sep. 30, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2023
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. AERC is a wholly-owned subsidiary of Avista Corp. The primary subsidiary of AERC is AEL&P, which comprises Avista Corp.'s regulated utility operations in Alaska. Avista Capital, a wholly owned non-regulated subsidiary of Avista Corp., is the parent company of the subsidiary companies in the non-utility businesses, with the exception of AJT Mining Properties, Inc., which is a subsidiary of AERC. See Note 17 for b usiness segment information. Basis of Reporting The condensed consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying condensed consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants. 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. Derivative Assets and Liabilities Derivatives are recorded as either assets or liabilities on the Condensed Consolidated Balance Sheets measured at estimated fair value. The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and costs result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rate cases. The resulting regulatory assets associated with energy commodity derivative instruments are probable of recovery through future rates. Substantially all forward contracts to purchase or sell power and natural gas are recorded as derivative assets or liabilities at estimated fair value with an offsetting regulatory asset or liability. Contracts not considered derivatives are accounted for on the accrual basis until they are settled or realized unless there is a decline in the fair value of the contract determined to be other-than-temporary. 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 Condensed Consolidated Balance Sheets. Fair Value Measurements Fair value represents the price that would be received when selling an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. Energy commodity derivative assets and liabilities, deferred compensation assets, some equity investments, as well as derivatives related to interest rate swaps and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 12 for the Company’s fair value disclosures. Contingencies The Company has unresolved regulatory, legal and tax issues which have inherently uncertain outcomes. The Company accrues a loss contingency if it is probable a liability has been incurred and the amount of the loss or impairment can be reasonably estimated. The Company also discloses loss contingencies that do not meet these conditions for accrual if there is a reasonable possibility that a material loss may be incurred. See Note 16 for further discussion of the Company's commitments and contingencies.

New Accounting Standards

New Accounting Standards	9 Months Ended
	Sep. 30, 2023
Accounting Standards Update and Change in Accounting Principle [Abstract]
New Accounting Standards	NOTE 2. NEW ACCO UNTING STANDARDS ASU 2022-03 "Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions" In June 2022, the FASB issued ASU 2022-03, Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions. The purpose of this guidance is to clarify that a contractual restriction on the ability to sell an equity security is not considered part of the unit of account of the equity security, and therefore should not be considered when measuring the equity security's fair value. Additionally, an entity cannot separately recognize and measure a contractual sale restriction. This guidance also adds specific disclosures related to equity securities subject to contractual sale restrictions, including (i) the fair value of equity securities subject to contractual sale restrictions reflected in the balance sheet, (ii) the nature and remaining duration of the restrictions and (iii) the circumstances that could cause a lapse in the restrictions. The amendments are effective on January 1, 2024, with early adoption permitted. The amendments must be applied using a prospective approach with any adjustments from the adoption of the amendments recognized in earnings and disclosed upon adoption. The Company expects these amendments to only affect its disclosure requirements.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2023
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	NOTE 3. BALANCE SHEET COMPONENTS Inventory Inventories of materials and supplies, emission allowances, fuel stock and stored natural gas are recorded at average cost and consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Materials and supplies $ 80,916 $ 75,766 Emission allowances 40,842 — Stored natural gas 17,841 26,788 Fuel stock 5,575 5,120 Total $ 145,174 $ 107,674 Other Current Assets Other current assets consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Prepayments $ 51,194 $ 30,201 Income taxes receivable 32,157 30,740 Derivative assets net of collateral 1,981 18,198 Collateral posted for derivative instruments after netting with outstanding — 66,142 Other 8,257 5,886 Total $ 93,589 $ 151,167 Net Utility Property Net utility property, which is recorded at original cost, net of accumulated depreciation, consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Utility plant in service $ 7,708,173 $ 7,561,688 Construction work in progress 199,365 164,147 Total 7,907,538 7,725,835 Less: Accumulated depreciation and amortization 2,282,470 2,281,126 Total $ 5,625,068 $ 5,444,709 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 September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Equity investments $ 154,873 $ 147,809 Operating lease ROU assets 68,087 68,238 Finance lease ROU assets 37,324 40,056 Non-utility property 30,909 25,401 Notes receivable 18,234 17,954 Long-term prepaid license fees 16,293 17,936 Pension asset 22,268 13,382 Investment in affiliated trust 11,547 11,547 Deferred compensation assets 7,763 7,541 Other 22,919 15,221 Total $ 390,217 $ 365,085 Other Current Liabilities Other current liabilities consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, Accrued taxes other than income taxes $ 29,722 $ 38,568 Derivative liabilities 19,684 26,910 Employee paid time off accruals 31,231 29,279 Accrued interest 42,610 20,863 Deferred wholesale revenue — 8,481 Pensions and other postretirement benefits 14,327 15,625 Other 45,227 49,689 Total $ 182,801 $ 189,415 Other Non-Current Liabilities and Deferred Credits Other non-current liabilities and deferred credits consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, Operating lease liabilities $ 67,088 $ 64,284 Finance lease liabilities 39,945 42,495 Deferred investment tax credits 28,371 28,784 Climate Commitment Act obligations 30,457 — Asset retirement obligations 16,024 15,783 Derivative liabilities 14,035 7,892 Other 16,786 16,617 Total $ 212,706 $ 175,855 Regulatory Assets and Liabilities Regulatory assets and liabilities consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, 2023 December 31, 2022 Current Non-Current Current Non-Current Regulatory Assets Energy commodity derivatives $ 45,144 $ 13,715 $ 112,090 $ 18,185 Decoupling surcharge 2,087 3,407 6,250 5,449 Deferred natural gas costs 84,851 — 52,091 — Deferred power costs 34,751 17,766 23,356 24,043 Deferred income taxes — 242,498 — 240,325 Pension and other postretirement benefit plans — 131,269 — 135,337 Interest rate swaps — 181,050 — 185,919 AFUDC above FERC allowed rate — 49,778 — 51,649 Settlement with Coeur d'Alene Tribe — 36,972 — 37,809 Advanced meter infrastructure — 30,104 — 32,381 Utility plant abandoned — 30,362 — 24,389 Deferred Climate Commitment Act costs — 30,760 — — COVID-19 deferrals — 10,170 — 9,793 Unamortized debt repurchase costs — 5,817 — 6,177 Demand side management programs — 2,728 — 3,683 Other regulatory assets 1,094 68,703 — 58,189 Total regulatory assets $ 167,927 $ 855,099 $ 193,787 $ 833,328 Regulatory Liabilities Income tax related liabilities $ 41,680 $ 357,812 $ 73,267 $ 390,734 Deferred natural gas costs 6,599 — — — Deferred power costs — 3,712 — — Decoupling rebate 13,644 21,327 9,469 20,476 Utility plant retirement costs — 411,250 — 376,817 Interest rate swaps — 26,681 — 24,204 Deferred Climate Commitment Act revenues — 21,675 — — COVID-19 deferrals — 10,640 — 11,874 Other regulatory liabilities 11,920 10,620 12,929 16,732 Total regulatory liabilities $ 73,843 $ 863,717 $ 95,665 $ 840,837

Revenue

Revenue	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Revenue	NOTE 4. REVENUE The core principle of the revenue recognition accounting model is that an entity should identify the various performance obligations in a contract, allocate the transaction price among the performance obligations and recognize revenue when (or as) the entity satisfies each performance obligation. Utility Revenues Revenue from Contracts with Customers General The majority of Avista Corp.’s revenue is from rate-regulated sales of electricity and natural gas to retail customers, which has two performance obligations, (1) having service available for a specified period (typically a month at a time) and (2) the delivery of energy to customers. The total energy price generally has a fixed component (basic charge) related to having service available and a usage-based component, related to the delivery and consumption of energy. The commodity is sold and/or delivered to and consumed by the customer simultaneously, and the provisions of the relevant utility commission authorization determine the charges the Company may bill the customer. Given that all revenue recognition criteria are met upon the delivery of energy to customers, revenue is recognized immediately at that time. Revenues from contracts with customers are presented in the Condensed Consolidated Statements of Income in the line item "Utility revenues, exclusive of alternative revenue programs." Non-Derivative Wholesale Contracts The Company has certain wholesale contracts which are not accounted for as derivatives and, accordingly, are considered revenue from contracts with customers. Revenue is recognized as energy is delivered to the customer or the service is available for a specified period of time, consistent with the discussion of rate-regulated sales above. Alternative Revenue Programs (Decoupling) ASC 606 retained existing GAAP associated with alternative revenue programs, which specified alternative revenue programs are contracts between an entity and a regulator of utilities, not a contract between an entity and a customer. GAAP requires an entity to present revenue arising from alternative revenue programs separately from revenues arising from contracts with customers on the face of the Condensed Consolidated Statements of Income. The Company's decoupling mechanisms (also known as a FCA in Idaho) qualify as alternative revenue programs. Decoupling revenue deferrals are recognized in the Condensed Consolidated Statements of Income during the period they occur (i.e. during the period of revenue shortfall or excess due to fluctuations in customer usage), subject to certain limitations, and a regulatory asset or liability is established that will be surcharged or rebated to customers in future periods. GAAP requires that for any alternative revenue program, like decoupling, the revenue must be expected to be collected from customers within 24 months of the deferral to qualify for recognition in the current period Condensed Consolidated Statement of Income. Any amounts included in the Company's decoupling program not expected to be collected from customers within 24 months are not recorded in the financial statements until the period in which revenue recognition criteria are met. The amounts expected to be collected from customers within 24 months represents an estimate made by the Company on an ongoing basis due to it being based on the volumes of electric and natural gas sold to customers on a go-forward basis. The Company records alternative program revenues under the gross method, which is to amortize the decoupling regulatory asset/liability to the alternative revenue program line item on the Condensed 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 excluded from revenue from contracts with customers and therefore disclosed separately. The revenue or loss is recognized for these items upon the settlement/expiration of the derivative contract. Derivative revenue includes those transactions entered into and settled within the same month. Other Utility Revenue Other utility revenue includes rent, sales of materials, late fees and other charges that do not represent contracts with customers. Other utility revenue also includes the provision for earnings sharing. This revenue is excluded from revenue from contracts with customers, as this revenue does not represent items where a customer is a party that has contracted with the Company to obtain goods or services that are an output of the Company’s ordinary activities in exchange for consideration. As such, these revenues are presented separately from revenue from contracts with customers. Other Considerations for Utility Revenues Gross Versus Net Presentation Revenues and resource costs from Avista Utilities’ settled energy contracts “booked out” (not physically delivered) are reported on a net basis as part of derivative revenues. Utility-related taxes collected from customers (primarily state excise taxes and city utility taxes) are imposed on Avista Utilities as opposed to being imposed on 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 included in revenue from contracts with customers were as follows for the three and nine months ended September 30 (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Utility-related taxes $ 14,484 $ 14,049 $ 56,356 $ 51,091 Significant Judgments and Unsatisfied Performance Obligations The only significant judgments involving revenue recognition are estimates surrounding unbilled revenue and receivables from contracts with customers and estimates surrounding the amount of decoupling revenues that will be collected from customers within 24 months (discussed above). The Company has certain capacity arrangements, where the Company has a contractual obligation to provide either electric or natural gas capacity to its customers for a fixed fee. Most of these arrangements are paid for in arrears by the customers and do not result in deferred revenue and only result in receivables from the customers. The Company has one capacity agreement where the customer makes payments throughout the year. As of September 30, 2023, the Company estimates it had unsatisfied capacity performance obligations of $ 8.7 million , which will be recognized as revenue in future periods as the capacity is provided to the customers. These performance obligations are not reflected in the financial statements, as the Company has not received payment for these services. Disaggregation of Total Operating Revenue The following table disaggregates total operating revenue by segment and source for the three and nine months ended September 30 (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Avista Utilities Revenue from contracts with customers $ 285,821 $ 276,988 $ 1,058,725 $ 970,247 Derivative revenues 77,562 76,248 141,080 218,024 Alternative revenue programs 3,578 ( 5,850 ) ( 9,947 ) ( 28,420 ) Deferrals and amortizations for rate refunds to customers 124 156 769 25 Other utility revenues 2,588 2,113 7,792 7,166 Total Avista Utilities 369,673 349,655 1,198,419 1,167,042 AEL&P Revenue from contracts with customers 9,700 9,526 34,934 32,747 Deferrals and amortizations for rate refunds to customers — ( 49 ) — ( 614 ) Other utility revenues 151 160 474 464 Total AEL&P 9,851 9,637 35,408 32,597 Other non-utility revenues 102 154 367 419 Total operating revenues $ 379,626 $ 359,446 $ 1,234,194 $ 1,200,058 Utility Revenue from Contracts with Customers by Type and Service The following table disaggregates revenue from contracts with customers associated with the Company's electric operations for the three and nine months ended September 30 (dollars in thousands): 2023 2022 Avista AEL&P Total Utility Avista AEL&P Total Utility Three months ended September 30: ELECTRIC OPERATIONS Revenue from contracts with customers Residential $ 95,881 $ 3,186 $ 99,067 $ 94,451 $ 3,123 $ 97,574 Commercial 89,772 6,447 96,219 89,411 6,339 95,750 Industrial 29,584 — 29,584 30,090 — 30,090 Public street and highway lighting 2,005 67 2,072 1,810 64 1,874 Total retail revenue 217,242 9,700 226,942 215,762 9,526 225,288 Transmission 7,721 — 7,721 9,662 — 9,662 Other revenue from contracts with 9,353 — 9,353 11,457 — 11,457 Total electric revenue from contracts $ 234,316 $ 9,700 $ 244,016 $ 236,881 $ 9,526 $ 246,407 Nine months ended September 30: ELECTRIC OPERATIONS Revenue from contracts with customers Residential $ 305,203 $ 14,485 $ 319,688 $ 299,562 $ 13,740 $ 313,302 Commercial 252,344 20,257 272,601 253,694 18,824 272,518 Industrial 82,707 — 82,707 82,235 — 82,235 Public street and highway lighting 5,940 192 6,132 5,586 183 5,769 Total retail revenue 646,194 34,934 681,128 641,077 32,747 673,824 Transmission 24,143 — 24,143 22,764 — 22,764 Other revenue from contracts with 33,580 — 33,580 27,628 — 27,628 Total electric revenue from contracts $ 703,917 $ 34,934 $ 738,851 $ 691,469 $ 32,747 $ 724,216 The following table disaggregates revenue from contracts with customers associated with the Company's natural gas operations for the three and nine months ended September 30 (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Avista Utilities Avista Utilities Avista Utilities Avista Utilities NATURAL GAS OPERATIONS Revenue from contracts with customers Residential $ 29,372 $ 22,960 $ 218,212 $ 174,655 Commercial 15,381 11,978 113,183 86,335 Industrial and interruptible 3,480 1,930 13,136 7,238 Total retail revenue 48,233 36,868 344,531 268,228 Transportation 1,866 1,832 6,058 6,331 Other revenue from contracts with customers 1,406 1,407 4,219 4,219 Total natural gas revenue from contracts with customers $ 51,505 $ 40,107 $ 354,808 $ 278,778

Leases

Leases	9 Months Ended
	Sep. 30, 2023
Leases [Abstract]
Leases	NOTE 5. LE ASES In March 2023, the Company entered into an agreement with Rathdrum Power, LLC (Rathdrum) amending and restating a PPA for the output of the Lancaster plant, a 270 MW natural gas-fired combined cycle combustion turbine. The restated PPA meets the definition of a lease, and all payments are variable in nature, based on capacity, usage or performance of the plant. Therefore, there is no lease obligation or corresponding ROU asset recorded by the Company. The Company previously had a variable interest in Rathdrum through the PPA, but did not consider itself the primary beneficiary of the entity. As a result of entering the amended and restated PPA, the Company reconsidered whether Rathdrum is a variable interest entity, concluding Rathdrum no longer meets the definition of a variable interest entity. This conclusion does not materially impact the Company's financial statements.

Derivatives and Risk Management

Derivatives and Risk Management	9 Months Ended
	Sep. 30, 2023
Derivative Instruments and Hedges, Assets [Abstract]
Derivatives and Risk Management	NOTE 6. DERIVATIVES AND RISK MANAGEMENT Energy Commodity Derivatives Avista Corp. is exposed to market risks relating to changes in electricity and natural gas commodity prices and certain other fuel prices. Market risk is, in general, the risk of fluctuation in the market price of the commodity being traded and is influenced primarily by supply and demand. Market risk includes the fluctuation in the market price of associated derivative commodity instruments. Avista Corp. utilizes derivative instruments, such as forwards, futures, swap derivatives and options, to manage the various risks relating to these commodity price exposures. Avista Corp. has an energy resources risk policy and control procedures to manage these risks. As part of Avista Corp.'s resource procurement and management operations in the electric business, Avista Corp. engages in an ongoing process of resource optimization, which involves the economic selection from available energy resources to serve Avista Corp.'s load obligations and the use of these resources to capture available economic value through wholesale market transactions. These include sales and purchases of electric capacity and energy, fuel for electric generation, and derivative contracts related to capacity, energy and fuel. Such transactions are part of the process of matching resources with load obligations and hedging a portion of the related financial risks. These transactions range from terms of intra-hour up to multiple years. As part of its resource procurement and management of its natural gas business, Avista Corp. makes continuing projections of its natural gas loads and assesses available natural gas resources including natural gas storage availability. Natural gas resource planning typically includes peak requirements, low and average monthly requirements and delivery constraints from natural gas supply locations to Avista Corp.’s distribution system. However, daily variations in natural gas demand can be significantly different than monthly demand projections. Based on these projections, Avista Corp. plans and executes a series of transactions to hedge a portion of its projected natural gas requirements through forward market transactions and derivative instruments. These transactions may extend as much as three natural gas operating years (November through October) into the future. Avista Corp. also leaves a significant portion of its natural gas supply requirements unhedged for purchase in short-term and spot markets. Avista Corp. plans for sufficient natural gas delivery capacity to serve its retail customers for a theoretical peak day event. Avista Corp. generally has more pipeline and storage capacity than what is needed during periods other than a peak-day. Avista Corp. optimizes its natural gas resources by using market opportunities to generate economic value that mitigates the fixed costs. Avista Corp. also optimizes its natural gas storage capacity by purchasing and storing natural gas when prices are traditionally lower, typically in the summer, and withdrawing during higher priced months, typically during the winter. However, if market conditions and prices indicate that Avista Corp. should buy or sell natural gas at other times during the year, Avista Corp. engages in optimization transactions to capture value in the marketplace. Natural gas optimization activities include, but are not limited to, wholesale market sales of surplus natural gas supplies, purchases and sales of natural gas to optimize use of pipeline and storage capacity, and participation in the transportation capacity release market. The following table presents the underlying energy commodity derivative volumes as of September 30, 2023 expected to be delivered or mature in the respective years shown (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical Financial Physical Financial Physical Financial Physical Financial Remainder 2023 5 — 12,377 33,810 74 267 735 5,295 2024 7 — 14,810 61,090 31 400 1,370 11,965 2025 — — 6,363 14,130 — 96 1,115 1,125 2026 — — 1,660 1,800 — — — — As of September 30, 2023 , there were no expected deliveries of energy commodity derivatives after 2 0 26. The following table presents the underlying energy commodity derivative volumes as of December 31, 2022 expected to be delivered or mature in the respective years shown (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical Financial Physical Financial Physical Financial Physical Financial 2023 5 — 19,140 79,253 136 1,011 4,145 29,473 2024 — — 533 30,658 — — 1,370 9,668 2025 — — 450 4,895 — — 1,115 1,125 As of December 31, 2022 , there were no expected deliveries of energy commodity derivatives after 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 recovered through retail rates from customers. Foreign Currency Exchange Derivatives A significant portion of Avista Corp.’s natural gas supply (including fuel for power generation) is obtained from Canadian sources. Most of those transactions are executed in U.S. dollars, which avoids foreign currency risk. A portion of Avista Corp.’s short-term natural gas transactions and long-term Canadian transportation contracts are committed based on Canadian currency prices. The short-term natural gas transactions are settled within 60 days with U.S. dollars. Avista Corp. hedges a portion of the foreign currency risk by purchasing Canadian currency exchange derivatives when such commodity transactions are initiated. The foreign currency exchange derivatives and the unhedged foreign currency risk have not had a material effect on Avista Corp.’s financial condition, results of operations or cash flows and these differences in cost related to currency fluctuations are included with natural gas supply costs for ratemaking. The following table summarizes the foreign currency exchange derivatives outstanding as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Number of contracts 20 19 Notional amount (in United States dollars) $ 5,292 $ 8,563 Notional amount (in Canadian dollars) 7,159 11,659 Interest Rate Swap Derivatives Avista Corp. is affected by fluctuating interest rates related to a portion of its existing debt, and future borrowing requirements. Avista Corp. hedges a portion of its interest rate risk with financial derivative instruments, which may include interest rate swap derivatives. These interest rate swap derivatives are considered economic hedges against fluctuations in future cash flows associated with anticipated debt issuances. The following table summarizes the unsettled interest rate swap derivatives outstanding as of September 30, 2023 and December 31, 2022 (dollars in thousands): Balance Sheet Date Number of Notional Mandatory September 30, 2023 2 $ 20,000 2024 1 $ 10,000 2025 December 31, 2022 4 $ 40,000 2023 1 10,000 2024 See Note 10 for discussion of the issuance of first mortgage bonds and the related settlement of interest rate swaps in connection with the pricing of the bonds in March 2023. The fair value of outstanding interest rate swap derivatives can vary significantly from period to period depending on the total notional amount of swap derivatives outstanding and fluctuations in market interest rates compared to the interest rates fixed by the swaps. Avista Corp. is required to make cash payments to settle the interest rate swap derivatives when the fixed rates are higher than prevailing market rates at the date of settlement. Conversely, Avista Corp. receives cash to settle its interest rate swap derivatives when prevailing market rates at the time of settlement exceed the fixed swap rates. Summary of Outstanding Derivative Instruments The amounts recorded on the Condensed Consolidated Balance Sheet as of September 30, 2023 and December 31, 2022 reflect the offsetting of derivative assets and liabilities where a legal right of offset exists. The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of September 30, 2023 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Gross Collateral Net Asset Foreign currency exchange derivatives Other current assets $ 23 $ — $ — $ 23 Interest rate swap derivatives Other property and investments-net and other non-current assets 6,379 — — 6,379 Energy commodity derivatives Other current assets 3,622 ( 1,664 ) — 1,958 Other property and investments-net and other non-current assets 534 ( 214 ) — 320 Other current liabilities 23,784 ( 70,886 ) 27,418 ( 19,684 ) Other non-current liabilities and deferred credits 4,378 ( 18,413 ) — ( 14,035 ) Total derivative instruments recorded on the balance sheet $ 38,720 $ ( 91,177 ) $ 27,418 $ ( 25,039 ) The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2022 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Gross Collateral Net Asset Foreign currency exchange derivatives Other current assets $ 43 $ — $ — $ 43 Other current liabilities — ( 3 ) — ( 3 ) Interest rate swap derivatives Other current assets 8,536 — — 8,536 Other property and investments-net and other non-current assets 2,648 — — 2,648 Other current liabilities — ( 52 ) — ( 52 ) Energy commodity derivatives Other current assets 32,257 ( 22,638 ) — 9,619 Other property and investments-net and other non-current assets 312 ( 16 ) — 296 Other current liabilities 107,902 ( 229,607 ) 94,850 ( 26,855 ) Other non-current liabilities and deferred credits 6,049 ( 24,530 ) 10,589 ( 7,892 ) Total derivative instruments recorded on the balance sheet $ 157,747 $ ( 276,846 ) $ 105,439 $ ( 13,660 ) Exposure to Demands for Collateral Avista Corp.'s derivative contracts often require collateral (in the form of cash or letters of credit) or other credit enhancements, or reductions or terminations of a portion of the contract through cash settlement. In the event of changes in market prices or a downgrade in Avista Corp.'s credit ratings or other established credit criteria, additional collateral may be required. In periods of price volatility, the level of exposure can change significantly. As a result, sudden and significant demands may be made against Avista Corp.'s credit facilities and cash. Avista Corp. actively monitors the exposure to possible collateral calls and takes steps to mitigate capital requirements. The following table presents Avista Corp.'s collateral outstanding related to its derivative instruments as of September 30, 2023 and December 31, 2022 (in thousands): September 30, December 31, 2023 2022 Energy commodity derivatives Cash collateral posted $ 27,418 $ 171,581 Letters of credit outstanding 9,000 49,425 Balance sheet offsetting 27,418 105,439 No letters of credit or cash collateral were outstanding related to interest rate swap derivatives a s of September 30, 2023 and December 31, 2022. 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 in a liability position and the amount of additional collateral Avista Corp. could be required to post as of September 30, 2023 (in thousands): September 30, 2023 Interest rate swap derivatives Liabilities with credit-risk-related contingent features $ — Additional collateral to post — Energy commodity derivatives Liabilities with credit-risk-related contingent features 5,334 Additional collateral to post 3,996

Pension Plans and Other Postret

Pension Plans and Other Postretirement Benefit Plans	9 Months Ended
	Sep. 30, 2023
Retirement Benefits, Description [Abstract]
Pension Plans and Other Postretirement Benefit Plans	NOTE 7. PENSION PLANS AND OTHE R POSTRETIREMENT BENEFIT PLANS Avista Utilities The Company contributed $ 10.0 million in cash to the pension plan for the nine months ended September 30, 2023 , and does no t expect further contributions in 2023. The Company uses a December 31 measurement date for its defined benefit pension and other postretirement benefit plans. The following table sets forth the components of net periodic benefit costs for the three and nine months ended September 30 (dollars in thousands): Pension Benefits Other Postretirement Benefits 2023 2022 2023 2022 Three months ended September 30: Service cost $ 3,098 $ 5,914 $ 559 $ 1,095 Interest cost 8,524 6,578 1,872 1,343 Expected return on plan assets ( 10,922 ) ( 10,950 ) ( 891 ) ( 700 ) Amortization of prior service cost (credit) 123 75 ( 263 ) ( 275 ) Net loss (gain) recognition 1,184 997 ( 54 ) 826 Net periodic benefit cost $ 2,007 $ 2,614 $ 1,223 $ 2,289 Nine months ended September 30: Service cost $ 11,092 $ 17,914 $ 1,909 $ 3,255 Interest cost 24,277 20,005 4,825 4,167 Expected return on plan assets ( 32,766 ) ( 32,851 ) ( 2,673 ) ( 2,100 ) Amortization of prior service cost (credit) 369 225 ( 789 ) ( 825 ) Net loss recognition 3,208 3,084 471 2,586 Net periodic benefit cost $ 6,180 $ 8,377 $ 3,743 $ 7,083 Total service costs in the table above are recognized in the same accounts as the associated labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses. The non-service portion of costs in the table above are recorded to other expense below income from operations in the Condensed Consolidated Statements of Income or capitalized as a regulatory asset. Approximately 40 percent of the costs are capitalized to regulatory assets and 60 percent is expensed to the income statement.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Taxes	NOTE 8. IN COME TAXES In accordance with interim reporting requirements, the Company uses an estimated annual effective tax rate for computing its provisions for income taxes. An estimate of annual income tax expense (or benefit) is made each interim period using estimates for annual pre-tax income, income tax adjustments, and tax credits. The estimated annual effective tax rates do not include discrete events such as tax law changes, examination settlements, accounting method changes, or adjustments to tax expense or benefits attributable to prior years. Discrete events are recorded in the interim period in which they occur or become known. The estimated annual tax rate is applied to year-to-date pre-tax income to determine income tax expense (or benefit) for the interim period consistent with the annual estimate. In subsequent interim periods, income tax expense (or benefit) for the period is computed as the difference between the year-to-date amount reported for the previous interim period and the current period’s year-to-date amount. The following table summarizes the significant factors impacting the difference between the Company's effective tax rate and the federal statutory rate for the three and nine months ended September 30 (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Federal income taxes at statutory rates $ 2,294 21.0 % $ ( 1,185 ) 21.0 % $ 14,872 21.0 % $ 13,764 21.0 % Increase (decrease) in tax resulting from: Flow through related to deduction of meters ( 3,744 ) ( 34.3 ) 1,192 ( 21.1 ) ( 22,956 ) ( 32.4 ) ( 18,643 ) ( 28.4 ) Tax effect of regulatory treatment of utility ( 828 ) ( 7.6 ) 420 ( 7.5 ) ( 6,040 ) ( 8.5 ) ( 6,878 ) ( 10.5 ) State income tax expense 151 1.4 ( 45 ) 0.8 949 1.3 856 1.3 Tax credits ( 862 ) ( 7.9 ) — — ( 1,997 ) ( 2.8 ) — — Settlement of prior year tax returns ( 867 ) ( 7.9 ) ( 318 ) 5.6 ( 867 ) ( 1.2 ) ( 318 ) ( 0.5 ) Uncertain tax positions 184 1.7 — — 184 0.2 — — Other ( 114 ) ( 1.0 ) 93 ( 1.6 ) ( 369 ) ( 0.5 ) ( 459 ) ( 0.7 ) Total income tax benefit $ ( 3,786 ) ( 34.6 )% $ 157 ( 2.8 )% $ ( 16,224 ) ( 22.9 )% $ ( 11,678 ) ( 17.8 )% (1) The Company's general rate cases included approval of base rate increases, offset by tax customer credits. As the tax customer credits are returned to customers, this results in a decrease to income tax expense as a result of flowing through the benefits related to meters and mixed service costs. The decrease in income tax expense offsets the increases in base rates granted to the Company in these general rate cases.

Short-Term Borrowings

Short-Term Borrowings	9 Months Ended
	Sep. 30, 2023
Short-Term Debt [Abstract]
Short-Term Borrowings	NOTE 9. S HORT-TERM BORROWINGS Avista Corp. Lines of Credit Avista Corp. has a committed line of credit in the total amount of $ 500 million, with an expiration date of June 2028 and the option to extend for two additional one year periods (subject to customary conditions). In June 2023, the then-existing agreement was amended to increase the capacity of the committed line of credit from $ 400 million to $ 500 million, extend the expiration date and replace the London Interbank Offered Rate (LIBOR) provisions with SOFR provisions. The committed line of credit is secured by non-transferable first mortgage bonds of Avista Corp. issued to the agent bank that would only be payable in the event, and then only to the extent, Avista Corp. defaults on its obligations under the committed line of credit. The bonds would bear interest at a rate of 12 percent. Balances outstanding and interest rates on borrowings (excluding letters of credit) under Avista Corp.’s revolving committed line of credit were as follows as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Borrowings outstanding at end of period $ 220,000 $ 313,000 Letters of credit outstanding at end of period 4,638 35,563 Average interest rate on borrowings at end of period 6.42 % 5.31 % In December 2022, Avista Corp. entered into a revolving credit agreement in the amount of $ 100 million. As of December 31, 2022, Avista Corp. did no t have any outstanding borrowings under this agreement. The agreement was terminated in June 2023 . The borrowings outstanding under Avista Corp.'s committed lines of credit were classified as short-term borrowings on the Condensed Consolidated Balance Sheets. 2022 Term Loan In December 2022, Avista Corp. entered into a term loan agreement in the amount of $ 150 million with a maturity date of March 30, 2023 . Avista Corp. borrowed the entire $ 150 million available under the agreement in 2022, and repaid the entire outstanding balance in March 2023. 2022 Letter of Credit Facility In December 2022, Avista Corp. entered into a letter of credit a greement in the aggregate amount of $ 50 million. Either party may terminate the agreement at any time. Avista Corp. had $ 9.0 million and $ 18.5 million in letters of credit outstanding under this agreement as of September 30, 2023 and December 31, 2022, respectively. Letters of credit are not reflected on the Condensed Consolidated Balance Sheets. If a letter of credit were drawn upon by the holder, we would have an immediate obligation to reimburse the bank that issued the letter. Covenants and Default Provisions The short-term borrowing agreements contain customary covenants and default provisions, including a change in control (as defined in the agreements). The events of default under each of the credit facilities also include a cross default from other indebtedness (as defined) and, in the case of the letter of credit agreement, other obligations. The committed line of credit agreement also includes 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 September 30, 2023, the Company was in compliance with this covenant. AEL&P AEL&P has a committed line of credit in the amount of $ 25.0 million that expires in June 2028 . There was $ 1.5 million outstanding under this agreement as of September 30, 2023 , and no borrowings or letters of credit outstanding under this agreement as of December 31, 2022 . 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.

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2023
Debt Disclosure [Abstract]
Long Term Debt	NOTE 10. LONG-TERM DEBT In March 2023, the Company issued and sold $ 250.0 mi llion of 5.66 percent first mortgage bonds due in 2053 with institutional investors in the private placement market. In connection with the pricing of the first mortgage bonds in March 2023, the Company cash-settled four interest rate swap derivatives (notional aggregate amount of $ 40.0 million) and received a net amount of $ 7.5 million, which will be amortized as a component of interest expense over the life of the debt. See Note 6 for a discussion of interest rate swap derivatives. A portion of the net proceeds from the sale of these bonds was used for the construction or improvement of utility facilities, and a portion was used to refinance existing indebtedness, including the repayment of Avista Corp.'s $ 150 million term loan.

Long-Term Debt to Affiliated Tr

Long-Term Debt to Affiliated Trusts	9 Months Ended
	Sep. 30, 2023
Long Term Debt To Affiliated Trust [Abstract]
Long- Term Debt To Affiliated Trusts	NOTE 11. 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. Effective July 3, 2023, the reference to LIBOR in the formulation for the distribution rate on these securities was replaced with three-month CME Term SOFR, as calculated and published by CME Group Benchmark Administration, Ltd. (a successor administrator), plus a tenor spread adjustment of 0.26 percent. Accordingly, the distribution rate on the Preferred Trust Securities will now be the three-month CME Term SOFR plus 1.137 percent calculated and reset quarterly. The distribution rates were as follows during the nine months ended September 30, 2023 and the year ended December 31, 2022: September 30, December 31, 2023 2022 Low distribution rate 5.64 % 1.05 % High distribution rate 6.55 % 5.64 % Distribution rate at the end of the period 6.55 % 5.64 % Concurrent with the issuance of the Preferred Trust Securities, Avista Capital II issued $ 1.5 million of Common Trust Securities to the Company. The Preferred Trust Securities may be redeemed at the option of Avista Capital II at any time and mature on June 1, 2037. In December 2000, the Company purchased $ 10.0 million of these Preferred Trust Securities. The Company owns 100 percent of Avista Capital II and has solely and unconditionally guaranteed the payment of distributions on, and redemption price and liquidation amount for, the Preferred Trust Securities to the extent 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 condensed consolidated financial statements as Avista Corp. is not the primary beneficiary. As such, the sole assets of the capital trusts are $ 51.5 million of junior subordinated deferrable interest debentures of Avista Corp., which are reflected on the Condensed Consolidated Balance Sheets. Interest expense to affiliated trusts in the Condensed Consolidated Statements of Income represents interest expense on these debentures.

Fair Value

Fair Value	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value	NOTE 12. FAIR VALUE The carrying values of cash and cash equivalents, accounts and notes receivable, accounts payable, and short-term borrowings as shown on the Condensed Consolidated Balance Sheets are reasonable estimates of their fair values. The carrying values of long-term debt (including current portion and material finance leases) and long-term debt to affiliated trusts as shown on the Condensed Consolidated Balance Sheets may be different from the estimated fair value. See below for the estimated fair value of long-term debt and long-term debt to affiliated trusts. The fair value hierarchy prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to fair values derived from unobservable inputs (Level 3 measurement). The three levels of the fair value hierarchy are defined as follows: Level 1 – Quoted prices are available in active markets for identical assets or liabilities. Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 – Pricing inputs are other than quoted prices in active markets included in Level 1, but which are either directly or indirectly observable as of the reporting date. Level 2 includes those financial instruments valued using models or other valuation methodologies. These models are primarily industry-standard models that consider various assumptions, including quoted forward prices for commodities, time value, volatility factors, and current market and contractual prices for the underlying instruments, as well as other relevant economic measures. Substantially all of these assumptions are observable in the marketplace throughout the full term of the instrument, can be derived from observable data or are supported by observable levels at which transactions are executed in the marketplace. Level 3 – Pricing inputs include significant inputs generally unobservable from objective sources. These inputs may be used with internally developed methodologies that result in management’s best estimate of fair value. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy levels. The determination of the fair values incorporates various factors including the credit standing of the counterparties involved and the impact of credit enhancements (such as cash deposits and letters of credit), and the impact of Avista Corp.’s nonperformance risk on its liabilities. The following table sets forth the carrying value and estimated fair value of the Company’s financial instruments not reported at estimated fair value on the Condensed Consolidated Balance Sheets as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, 2023 December 31, 2022 Carrying Estimated Carrying Estimated Long-term debt (Level 2) $ 1,100,000 $ 886,339 $ 1,113,500 $ 966,881 Long-term debt (Level 3) 1,450,000 1,030,511 1,200,000 881,480 Snettisham finance lease obligation (Level 3) 43,304 38,200 45,730 41,700 Long-term debt to affiliated trusts (Level 3) 51,547 45,021 51,547 42,836 These estimates of fair value of long-term debt and long-term debt to affiliated trusts were primarily based on available market information, which generally consists of estimated market prices from third party brokers for debt with similar risk and terms. The price ranges obtained from the third party brokers consisted of market prices of 54.44 percent to 100.08 percent of the principal amount, where 100.0 percent of the principal amount (adjusted for unamortized discount or premium) represents the carrying value recorded on the Condensed Consolidated Balance Sheets. Level 2 long-term debt represents publicly issued bonds with quoted market prices; however, due to their limited trading activity, they are classified as Level 2 because brokers must generate quotes and make estimates if there is no trading activity near a period end. Level 3 long-term debt consists of private placement bonds and debt to affiliated trusts, which typically have no secondary trading activity. Fair values in Level 3 are estimated based on market prices from third party brokers using secondary market quotes for debt with similar risk and terms to generate quotes for Avista Corp. bonds. Due to the unique nature of the Snettisham 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 September 30, 2023 and December 31, 2022. The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Condensed Consolidated Balance Sheets as of September 30, 2023 and December 31, 2022 at fair value on a recurring basis (dollars in thousands): Level 1 Level 2 Level 3 Counterparty Total September 30, 2023 Assets: Energy commodity derivatives $ — $ 32,318 $ — $ ( 30,040 ) $ 2,278 Foreign currency exchange derivatives — 23 — — 23 Interest rate swap derivatives — 6,379 — — 6,379 Equity Investments — — 50,477 — 50,477 Deferred compensation assets Mutual Funds: Fixed income securities (3) 1,119 — — — 1,119 Equity securities (3) 6,466 — — — 6,466 Total $ 7,585 $ 38,720 $ 50,477 $ ( 30,040 ) $ 66,742 Liabilities: Energy commodity derivatives (2) $ — $ 75,804 $ 15,373 $ ( 57,458 ) $ 33,719 Total $ — $ 75,804 $ 15,373 $ ( 57,458 ) $ 33,719 December 31, 2022 Assets: Energy commodity derivatives (2) $ — $ 146,232 $ 288 $ ( 136,605 ) $ 9,915 Foreign currency exchange derivatives — 43 — — 43 Interest rate swap derivatives — 11,184 — — 11,184 Equity Investments — — 54,284 — 54,284 Deferred compensation assets Mutual Funds: Fixed income securities (3) 1,267 — — — 1,267 Equity securities (3) 6,132 — — — 6,132 Total $ 7,399 $ 157,459 $ 54,572 $ ( 136,605 ) $ 82,825 Liabilities: Energy commodity derivatives (2) $ — $ 258,769 $ 18,022 $ ( 242,044 ) $ 34,747 Foreign currency exchange derivatives — 3 — — 3 Interest rate swap derivatives — 52 — — 52 Total $ — $ 258,824 $ 18,022 $ ( 242,044 ) $ 34,802 (1) The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties. (2) The Level 3 energy commodity derivative balances are associated with natural gas exchange agreements. (3) Included in other property and investments-net and other non-current assets on the Condensed Consolidated Balance Sheets. The difference between the amount of derivative assets and liabilities disclosed in respective levels in the table above and the amount of derivative assets and liabilities disclosed on the Condensed Consolidated Balance Sheets is due to netting arrangements with certain counterparties. See Note 6 for additional discussion of derivative netting. To establish fair value for energy commodity derivatives, the Company uses quoted market prices and forward price curves to estimate the fair value of energy commodity derivative instruments included in Level 2. In particular, electric derivative valuations are performed using market quotes, adjusted for periods in between quotable periods. Natural gas derivative valuations are estimated using New York Mercantile Exchange pricing for similar instruments, adjusted for basin differences, using market quotes. Where observable inputs are available for substantially the full term of the contract, the derivative asset or liability is included in Level 2. To establish fair values for interest rate swap derivatives, the Company uses forward market curves for interest rates for the term of the swaps and discounts the cash flows back to present value using an appropriate discount rate. The discount rate is calculated by third party brokers according to the terms of the swap derivatives and evaluated by the Company for reasonableness, with consideration given to the potential non-performance risk by the Company. Future cash flows of the interest rate swap derivatives are equal to the fixed interest rate in the swap compared to the floating market interest rate multiplied by the notional amount for each period. To establish fair value for foreign currency derivatives, the Company uses forward market curves for Canadian dollars against the U.S. dollar and multiplies the difference between the locked-in price and the market price by the notional amount of the derivative. Forward foreign currency market curves are provided by third party brokers. The Company's credit spread is factored into the locked-in price of the foreign exchange contracts. Deferred compensation assets and liabilities represent funds held by the Company in a Rabbi Trust for an executive deferral plan. These funds consist of actively traded equity and bond funds with quoted prices in active markets. Level 3 Fair Value Natural Gas Exchange Agreement For the natural gas commodity exchange agreement, the Company uses the same Level 2 market 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 are not 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 September 30, 2023 (dollars in thousands): Fair Value Valuation Unobservable Range and Weighted September 30, 2023 Technique Input Average Price Natural gas exchange agreement $ ( 15,373 ) Internally derived weighted average cost of gas Forward purchase prices $ 2.62 - $ 3.86 /mmBTU 3.30 Weighted Average Forward sales prices $ 3.22 - $ 11.65 /mmBTU 8.03 Weighted Average Purchase volumes 140,000 - 310,000 mmBTUs Sales volumes 75,000 - 310,000 mmBTUs The valuation methods, significant inputs and resulting fair values described above were developed by the Company's management and are reviewed on at least a quarterly basis to ensure they provide a reasonable estimate of fair value each reporting period. Equity Investments The Company has two equity investments measured at fair value on a recurring basis. For one investment, fair value is determined using a market approach, starting with enterprise values from recent market transaction data for comparable companies with similar equity instruments. The market transaction data was used to estimate an enterprise value of the underlying investment and that value was allocated to the various classes of equity via an option pricing model and a waterfall approach. The selection of appropriate comparable companies and the expected time to a liquidation event requires management judgment. The significant assumptions in the analysis include the comparable market transactions and related enterprise values, time to liquidity event and the market discount for lack of liquidity. In the event there are relevant market transactions for the same or similar securities of the subject company or there is the reasonable possibility of a transaction occurring, those transactions are utilized as an input to the valuation with a probability weight applied to the valuation. For the second investment, the fair value is determined using an income approach utilizing a discounted cash flow model. The model is based on income statement forecasts from the underlying company to determine cash flows for the period of ownership. The model then utilizes market multiples from publicly traded comparable companies in similar industries and projects to estimate the terminal fair value. The market multiples are reduced to reflect the difference in the life cycle between the publicly traded comparable companies and the start-up nature of the investment company. The selection of appropriate comparable companies, market multiples and the reduction to those market multiples requires management judgment. The significant assumptions in the model include the discount rate representing the risk associated with the investment, market multiples and the related reduction to those multiples, revenue forecasts, and the estimated terminal date for the investment. In the event there are relevant market transactions for the same or similar securities of the subject company or there is the reasonable possibility of a transaction occurring, those transactions are used to determine the fair value of Avista Corp.’s investment under a market approach instead of utilizing a discounted cash flow model. The market transactions are considered Level 3 inputs because they are not publicly available observable transactions. The following table presents the quantitative information which was used to estimate the fair values of the Level 3 equity investments as of September 30, 2023 (dollars in thousands): Fair Value at September 30, 2023 Valuation Technique Unobservable Input Range Equity investments $ 50,477 Market approach Comparable enterprise values $ 130,000 -$ 388,600 246,000 Average Time to liquidity event 1 year Discounted cash flows Revenue market multiples 0.42 x to 5.47 x Revenue 1.76 x Average Market exit reduction 50 % Discount rate 25 % Annual revenues $ 6,000 - $ 265,000 Terminal date 2026 The following table presents activity for assets and liabilities measured at fair value using significant unobservable inputs (Level 3) for the three and nine months ended September 30 (dollars in thousands): Natural Gas Exchange Agreement (1) Equity Investments Total Three Months Ended September 30, 2023: Beginning balance $ ( 11,721 ) $ 48,453 $ 36,732 Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities ( 3,652 ) — ( 3,652 ) Recognized in net income — 2,024 2,024 Ending balance as of September 30, 2023 $ ( 15,373 ) $ 50,477 $ 35,104 Three Months Ended September 30, 2022: Beginning balance $ ( 2,289 ) $ — $ ( 2,289 ) Transfers in (2) — 1,952 1,952 Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities ( 4,551 ) — ( 4,551 ) Recognized in net income — 3,829 3,829 Ending balance as of September 30, 2022 $ ( 6,840 ) $ 5,781 $ ( 1,059 ) Nine Months Ended September 30, 2023: Beginning balance $ ( 17,734 ) $ 54,284 $ 36,550 Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities 2,115 — 2,115 Recognized in net income — ( 3,174 ) ( 3,174 ) Purchases and debt conversions — 2,367 2,367 Settlements 246 — 246 Other — ( 3,000 ) ( 3,000 ) Ending balance as of September 30, 2023 $ ( 15,373 ) $ 50,477 $ 35,104 Nine Months Ended September 30, 2022: Beginning balance $ ( 7,771 ) $ — $ ( 7,771 ) Transfers in (2) — 1,952 1,952 Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities 3,144 — 3,144 Recognized in net income — 3,829 3,829 Settlements ( 2,213 ) — ( 2,213 ) Ending balance as of September 30, 2022 $ ( 6,840 ) $ 5,781 $ ( 1,059 ) (1) There were no purchases, issuances or transfers from other categories of any derivatives instruments during the periods presented in the table above. (2) The Company elected to measure certain equity investments at fair value on a recurring basis in 2022, as such the transfer in represents the value as of the election.

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2023
Stockholders' Equity Note [Abstract]
Common Stock	NOTE 13. CO MMON STOCK The Company issued common stock for total net proceeds of $ 28.6 million and $ 88.2 million during the three and nine months ended September 30, 2023, respectively. Most of these issuances came through the Company's sales agency agreements under which the Company may offer and sell new shares of common stock through its sales agents from time to time. Under these sales agency agreements, the Company issued 0.8 million and 2.3 million shares during the three and nine months ended September 30, 2023 .

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2023
Accumulated Other Comprehensive Loss [Abstract]
Accumulated Other Comprehensive Loss	NOTE 14. ACCUMULATED OT HER COMPREHENSIVE LOSS Accumulated other comprehensive loss, net of tax, consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, Unfunded benefit obligation for pensions and other postretirement benefit plans - 562 and $ 547 , respectively $ 2,114 $ 2,058 The following table details the reclassifications out of accumulated other comprehensive loss to net income by component for the three and nine months ended September 30 (dollars in thousands): Amounts Reclassified from Accumulated Other Three months ended September 30, Nine months ended September 30, Details about Accumulated Other Comprehensive Loss Components 2023 2022 2023 2022 Amortization of defined benefit pension and Amortization of net prior service cost (1) $ ( 140 ) $ ( 200 ) $ ( 420 ) $ ( 600 ) Amortization of net loss (1) 1,130 1,823 3,679 5,670 Adjustment due to effects of regulation (1) ( 1,014 ) ( 1,279 ) ( 3,330 ) ( 4,031 ) Total before tax (2) ( 24 ) 344 ( 71 ) 1,039 Tax expense (benefit) (2) 5 ( 72 ) 15 ( 218 ) Net of tax (2) $ ( 19 ) $ 272 $ ( 56 ) $ 821 (1) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details). (2) Description is also the affected line item on the Condensed Consolidated Statement of Income.

Earnings Per Common Share

Earnings Per Common Share	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Earnings Per Common Share	NOTE 15. EARNINGS PER COMMON SHAR E The following table presents the computation of basic and diluted earnings per common share for the three and nine months ended September 30 (in thousands, except per share amounts): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Numerator: Net income (loss) $ 14,716 $ ( 5,798 ) $ 87,045 $ 77,220 Denominator: Weighted-average number of common shares outstanding-basic 76,734 73,229 75,962 72,547 Effect of dilutive securities: Performance and restricted stock awards 27 69 94 82 Weighted-average number of common shares outstanding-diluted 76,761 73,298 76,056 72,629 Earnings (loss) per common share: Basic $ 0.19 $ ( 0.08 ) $ 1.15 $ 1.06 Diluted $ 0.19 $ ( 0.08 ) $ 1.14 $ 1.06 There were no shares excluded from the calculation because they were antidilutive.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE 16. 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 will vigorously protect and defend its interests and pursue its rights. However, no assurance can be given as to the ultimate outcome of any matter because litigation and other contested proceedings are inherently subject to numerous uncertainties. For matters affecting Avista Utilities’ or AEL&P's operations, the Company intends to seek, to the extent appropriate, recovery of incurred costs through the ratemaking process. Boyds Fire (State of Washington Department of Natural Resources (DNR) v. Avista) In August 2019, the Company was served with a complaint, captioned “State of Washington Department of Natural Resources v. Avista Corporation,” seeking recovery of up to $ 4.4 million for fire suppression and investigation costs and related expenses incurred in connection with a wildfire that occurred in Ferry County, Washington, in August 2018. Specifically, the complaint alleges the fire, which became known as the “Boyds Fire,” was caused by a dead ponderosa pine tree falling into an overhead distribution line, and 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 were subsequently filed by private landowners seeking property damages, and holders of insurance subrogation claims seeking recovery of insurance proceeds paid. The lawsuits were filed in the Superior Court of Ferry County, Washington. The Company continues to vigorously defend itself in the litigation. However, at this time the Company is unable to predict the likelihood of an adverse outcome or estimate a range of potential loss in the event of such an outcome. Road 11 Fire In April 2022, Avista Corp. received a notice of claim from property owners seeking damages of $ 5 million in connection with a fire that occurred in Douglas County, Washington, in July 2020. In June 2022, those claimants filed suit in the Superior Court of Douglas County, Washington, seeking unspecified damages. The fire, which was designated as the “Road 11 Fire,” occurred in the vicinity of an Avista Corp. 115kv line, resulting in damage to three overhead transmission structures. The fire occurred during a high wind event and grew to 10,000 acres before being contained. The Company disputes that it is liable for the fire and will vigorously defend itself in the pending legal proceeding; however, at this time the Company is unable to predict the likelihood of an adverse outcome or estimate a range of potential loss in the event of such an outcome. Labor Day 2020 Windstorm General In September 2020, a severe windstorm occurred in eastern Washington and northern Idaho. The extreme weather event resulted in customer outages and multiple wildfires in the region. The Company has become aware of instances where, during the 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. However, the Company's investigation has found no evidence of negligence with respect to any of those fires. Consistent with that conclusion, the statute of limitations with respect to the claims arising out of the Labor Day 2020 Windstorm has now passed and, with the exception of the Babb Road Fire discussed below, no legal action has been commenced. Babb Road Fire In May 2021 the Company learned the Washington Department of Natural Resources (DNR) had completed its investigation and issued a report on the Babb Road Fire. The Babb Road fire covered approximately 15,000 acres and destroyed approximately 220 structures. There are no reports of personal injury or death resulting from the fire. The DNR report concluded, among other things, that • the fire was ignited when a branch of a multi-dominant Ponderosa Pine tree was broken off by the wind and fell on an Avista Corp. distribution line; • the tree was located approximately 30 feet from the center of Avista Corp.’s distribution line and approximately 20 feet beyond Avista Corp.’s right-of-way; • the tree showed some evidence of insect damage, damage at the top of the tree from porcupines, a small area of scarring where a lateral branch/leader (LBL) had broken off in the past, and some past signs of Gall Rust disease. The DNR report concluded as follows: “It is my opinion that because of the unusual configuration of the tree, and its proximity to the powerline, a closer inspection was warranted. A nearer inspection of the tree should have revealed the cut LBL ends and its previous failure, and necessitated determination of the failure potential of the adjacent LBL, implicated in starting the Babb Road Fire.” The DNR report acknowledged that, other than the multi-dominant nature of the tree, the conditions mentioned above would not have been easily visible without close-up inspection of, or cutting into, the tree. The report also acknowledged that, while the presence of multiple tops would have been visible from the nearby roadway, the tree did not fail at a v-fork due to the presence of multiple tops. The Company contends that applicable inspection standards did not require a closer inspection of the otherwise healthy tree, nor was the Company negligent with respect to its maintenance, inspection or vegetation management practices. Eleven lawsuits have been filed in connection with the Babb Road fire. This includes a lawsuit filed by two individuals and a business entity on September 1, 2023. Asplundh Tree Company and CNUC Utility Consulting, which both perform vegetation management services as independent contractors to the Company, are also named as defendants in each of the lawsuits. The lawsuits include six subrogation actions filed by insurance companies seeking to recover approximately $ 23 million purportedly paid to insureds to date; four actions on behalf of individual plaintiffs seeking unspecified damages; and a class action lawsuit seeking unspecified damages. All proceedings were consolidated for discovery and pre-trial proceedings, are pending in the Superior Court of Spokane County Washington under the lead action Blakely v. Avista Corporation et al. , and variously assert causes of action for negligence, private nuisance, trespass and inverse condemnation (a theory of strict liability). On September 16, 2022, the Company filed a motion in the Superior Court of Spokane County, Washington, seeking dismissal of the Plaintiffs' inverse condemnation claims as a matter of law on the grounds that they are not legally cognizable under Washington law. On October 14, 2022, the Superior Court heard oral argument on that motion. The Court concluded the Company's motion involved mixed questions of law and fact, and, as a consequence, could not be granted at that stage of the proceedings; however, the Court indicated the Company could bring the issue before the Court again after discovery is completed. The Company will vigorously defend itself in the legal proceedings; however, at this time the Company is unable to predict the likelihood of an adverse outcome or estimate a range of potential loss in the event of such an outcome. August 2023 Fire Activity On August 18, 2023, a severe windstorm caused multiple fires in eastern Washington. This includes the Gray Fire, which started to the west of Medical Lake and quickly spread to the east, burning more than 10,000 acres and impacting approximately 240 homes. The Company’s investigation has determined that it did not have facilities near, nor were its facilities involved in, the origin of the Gray Fire. The Company’s facilities were secondarily impacted by the fire, and have since been repaired. On August 29, 2023, a fire started in windy conditions near Orofino, Idaho, burning 53 acres and six primary residences. The Company did have electrical facilities in the area of the fire; however, the Idaho Department of Lands’ investigation into the cause of the fire is ongoing. The Company is conducting an investigation internally, and has not yet reached any conclusions as to the origin of the fire. With the exception of one claim for personal property, the Company has not received any claims in connection with the fire. Colstrip Colstrip Owners Arbitration and Litigation Colstrip Units 3 and 4 are owned by the Company, PacifiCorp, Portland General Electric (PGE), and Puget Sound Energy (PSE) (collectively, the "Western Co-Owners"), as well as NorthWestern and Talen Montana, LLC (Talen), as tenants in common under an Ownership and Operating Agreement, dated May 6, 1981, as amended (O&O Agreement), in the percentages set forth below: Co-Owner Unit 3 Unit 4 Avista 15 % 15 % PacifiCorp 10 % 10 % PGE 20 % 20 % PSE 25 % 25 % NorthWestern — 30 % Talen 30 % — Colstrip Units 1 and 2, owned by PSE and Talen, were shut down in 2020 and are in the process of being decommissioned. The co-owners of Units 3 and 4 also own undivided interests in facilities common to both Units 3 and 4, as well as in certain facilities common to all four Colstrip units. The Washington Clean Energy Transformation Act (CETA), among other things, imposes deadlines by which each electric utility must eliminate from its electricity rates in Washington the costs and benefits associated with coal-fired resources, such as Colstrip. The practical impact of CETA is electricity from such resources, including Colstrip, may no longer be delivered to Washington retail customers after 2025. The co-owners of Colstrip Units 3 and 4 have differing needs for the generating capacity of these units. Accordingly, certain business disagreements have arisen among the co-owners, including, disagreements as to the requirements for shutting down these units. NorthWestern has initiated arbitration pursuant to the O&O Agreement to resolve these business disagreements, and two actions have been initiated to compel arbitration of those disputes: one by Talen in the Montana Thirteenth Judicial District Court for Yellowstone County, and one by the Western Co-Owners, which is pending in Montana Federal District Court. In light of the ownership transfer agreements discussed below, the Colstrip owners agreed to stay both the litigation and the arbitration through January 12, 2024, at which time the proceedings would resume absent further agreement between the owners. Agreement Between Talen Energy and Puget Sound Energy In September 2022, the Company received notice that PSE and Talen entered into an agreement through which PSE has agreed to transfer its 25 percent ownership in Colstrip Units 3 and 4 to Talen at the end of 2025. The terms and conditions of the agreement are similar in most respects to the NorthWestern Transaction discussed below. Agreement Between Avista and NorthWestern On January 16, 2023, the Company entered into an agreement with NorthWestern under which the Company will transfer its 15 percent ownership in Colstrip Units 3 and 4 to NorthWestern. There is no monetary exchange included in the transaction. The transaction is scheduled to close on December 31, 2025 or such other date as the parties mutually agree upon. Under the agreement, the Company will remain obligated through the close of the transaction to pay its share of (i) operating expenses, (ii) capital expenditures, but not in excess of the portion allocable pro rata to the portion of useful life (through 2030) expired through the close of the transaction, and (iii) except for certain costs relating to post-closing activities, site remediation expenses. In addition, the Company would enter into an agreement under which it would retain its voting rights with respect to decisions relating to remediation. The Company will retain its Colstrip transmission system assets, which are excluded from the transaction. Under the Colstrip O&O Agreement, each of the other owners of Colstrip has a 90-day period in which to evaluate the transaction and determine whether to exercise their respective rights of first refusal as to a portion of the generation being turned over to NorthWestern. That period was extended, by agreement of the Owners, through January 12, 2024. The transaction is subject to the satisfaction of customary closing conditions including the receipt of any required regulatory approvals, as well as NorthWestern's ability to enter into a new coal supply agreement by December 31, 2024. The Company does not expect this transaction to have a material impact on its financial results. Burnett et al. v. Talen et al. Multiple property owners initiated a legal proceeding (titled Burnett et al. v. Talen et al. ) in the Montana District Court for Rosebud County against Talen, PSE, PacifiCorp, PGE, Avista Corp., NorthWestern, and Westmoreland Rosebud Mining. The plaintiffs allege a failure to contain coal dust in connection with the operation of Colstrip, and seek unspecified damages. The Company will vigorously defend itself in the litigation, but at this time is unable to predict the outcome, nor an amount or range of potential impact in the event of an outcome adverse to the Company’s interests. Westmoreland Mine Permits Two lawsuits have been commenced by the Montana Environmental Information Center and others, challenging certain permits relating to the operation of the Westmoreland Rosebud Mine, which provides coal to Colstrip. In the first, the Montana District Court for Rosebud County issued an order vacating a permit for one area of the mine. In the second, the Montana Federal District Court vacated a decision by the federal Office of Surface Mining Reclamation and Enforcement approving expansion of the mine into a new area, pending further analysis of potential environmental impact. Both decisions have been appealed. Avista Corp. is not a party to either of these proceedings, but 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 surrounded by flood water in the Spokane River. The Company voluntarily reported its actions to the NPS several days later. Thereafter, in March 2018, the NPS notified the Company that it might seek recovery for unspecified costs and damages allegedly caused during the incident pursuant to the System Unit Resource Protection Act (SURPA), 54 U.S.C. 100721 et seq. In January 2021, the United States Department of Justice (DOJ) requested the Company and the DOJ renew discussions relating to the matter. In July 2021, the DOJ communicated that it may seek damages of approximately $ 2 million in connection with the incident for alleged damage to “natural and cultural resources”. In addition, the DOJ indicated that it may seek treble damages under the SURPA and state law, bringing its total potential claim to approximately $ 6 million. The Company disputes the position taken by the DOJ with respect to the incident, as well as the nature and extent of the DOJ’s alleged damages, and will vigorously defend itself in any litigation that may arise with respect to the matter. The Company and the DOJ have engaged in discussions to understand their respective positions and determine whether a resolution of the dispute may be possible. However, the Company cannot predict the outcome of the matter. Rathdrum, Idaho Natural Gas Incident In October 2021, there was an incident in Rathdrum, Idaho involving the Company’s natural gas infrastructure. The incident occurred after a third party damaged those facilities during excavation work. The incident resulted in a fire which destroyed one residence and resulted in minor injuries to the occupants. On January 23, 2023, the Company was served with a lawsuit filed in the District Court of Kootenai County, Idaho by one property owner, seeking unspecified damages. The Company intends to vigorously defend itself in this action. Climate Commitment Act (CCA) Obligations Effective January 1, 2023, the CCA went into effect in the State of Washington, requiring the Company to secure enough carbon allowances to cover its carbon emissions over a certain amount each year. The state has issued carbon allowances to cover electric retail sales. In May 2023, a model was approved for use in calculating the allowances needed for compliance which assumes hydroelectric generation is first used for wholesale sales, therefore reducing allowances required for wholesale sales. The Company expects to recover any costs incurred for its Washington operations through the ratemaking process. Other Contingencies In the normal course of business, the Company has various other legal claims and contingent matters outstanding. The Company believes any ultimate liability arising from these actions will not have a material impact on its financial condition, results of operations or cash flows. It is possible a change could occur in the Company’s estimates of the probability or amount of a liability being incurred. Such a change, should it occur, could be significant. See "Note 22 of the Notes to Consolidated Financial Statements" in the 2022 Form 10-K for additional discussion regarding other contingencies.

Information by Business Segment

Information by Business Segments	9 Months Ended
	Sep. 30, 2023
Segment Reporting [Abstract]
Information by Business Segments	NOTE 17. INFORMATION BY BUSINESS SEGMENTS The business segment presentation reflects the basis used by the Company's management to analyze performance and determine the allocation of resources. The Company's management evaluates performance based on income (loss) from operations before income taxes as well as net income (loss). The accounting policies of the segments are the same as those described in the summary of significant accounting policies. Avista Utilities' business is managed based on the total regulated utility operation; therefore, it is considered one segment. AEL&P is a separate reportable business segment, as it has separate financial reports reviewed in detail by the Chief Operating Decision Maker and its operations and risks are sufficiently different from Avista Utilities and the other businesses at AERC that it cannot be aggregated with 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 three months ended September 30, 2023: Operating revenues $ 369,673 $ 9,851 $ 379,524 $ 102 $ — $ 379,626 Resource costs 146,793 1,489 148,282 — — 148,282 Other operating expenses 98,609 3,860 102,469 603 — 103,072 Depreciation and amortization 64,125 2,735 66,860 45 — 66,905 Income (loss) from operations 37,081 1,552 38,633 ( 546 ) — 38,087 Interest expense (2) 33,896 1,456 35,352 538 ( 406 ) 35,484 Income tax expense (benefit) ( 3,845 ) 36 ( 3,809 ) 23 — ( 3,786 ) Net income 13,498 288 13,786 930 — 14,716 Capital expenditures (3) 127,666 4,865 132,531 — — 132,531 For the three months ended September 30, 2022: Operating revenues $ 349,655 $ 9,637 $ 359,292 $ 154 $ — $ 359,446 Resource costs 146,384 1,400 147,784 — — 147,784 Other operating expenses 98,062 3,639 101,701 1,041 — 102,742 Depreciation and amortization 60,780 2,704 63,484 32 — 63,516 Income (loss) from operations 18,660 1,661 20,321 ( 919 ) — 19,402 Interest expense (2) 28,214 1,489 29,703 243 ( 111 ) 29,835 Income tax expense (benefit) 197 21 218 ( 61 ) — 157 Net income (loss) ( 5,987 ) 228 ( 5,759 ) ( 39 ) — ( 5,798 ) Capital expenditures (3) 116,809 3,854 120,663 — — 120,663 For the nine months ended September 30 2023: Operating revenues $ 1,198,419 $ 35,408 $ 1,233,827 $ 367 $ — $ 1,234,194 Resource costs 478,947 3,507 482,454 — — 482,454 Other operating expenses 299,274 11,244 310,518 2,363 — 312,881 Depreciation and amortization 190,008 8,188 198,196 76 — 198,272 Income (loss) from operations 148,897 11,671 160,568 ( 2,072 ) — 158,496 Interest expense (2) 102,014 4,360 106,374 1,333 ( 942 ) 106,765 Income tax expense (benefit) ( 17,349 ) 2,048 ( 15,301 ) ( 923 ) — ( 16,224 ) Net income (loss) 83,935 5,689 89,624 ( 2,579 ) — 87,045 Capital expenditures (3) 347,264 12,013 359,277 — — 359,277 For the nine months ended September 30 2022: Operating revenues $ 1,167,042 $ 32,597 $ 1,199,639 $ 419 $ — $ 1,200,058 Resource costs 489,029 3,020 492,049 — — 492,049 Other operating expenses 289,828 10,882 300,710 4,907 — 305,617 Depreciation and amortization 180,765 8,102 188,867 94 — 188,961 Income (loss) from operations 121,476 9,760 131,236 ( 4,582 ) — 126,654 Interest expense (2) 81,864 4,463 86,327 508 ( 121 ) 86,714 Income tax expense (benefit) ( 14,728 ) 1,070 ( 13,658 ) 1,980 — ( 11,678 ) Net income 65,241 4,292 69,533 7,687 — 77,220 Capital expenditures (3) 324,123 7,186 331,309 756 — 332,065 Total Assets: As of September 30, 2023: $ 7,026,484 $ 271,192 $ 7,297,676 $ 190,853 $ ( 18,499 ) $ 7,470,030 As of December 31, 2022: $ 6,976,164 $ 264,322 $ 7,240,486 $ 187,027 $ ( 10,163 ) $ 7,417,350 (1) Intersegment eliminations reported as interest expense represent intercompany interest. (2) Including interest expense to affiliated trusts. (3) The capital expenditures for the other businesses are included in other investing activities on the Condensed Consolidated Statements of Cash Flows.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2023
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. AERC is a wholly-owned subsidiary of Avista Corp. The primary subsidiary of AERC is AEL&P, which comprises Avista Corp.'s regulated utility operations in Alaska. Avista Capital, a wholly owned non-regulated subsidiary of Avista Corp., is the parent company of the subsidiary companies in the non-utility businesses, with the exception of AJT Mining Properties, Inc., which is a subsidiary of AERC. See Note 17 for b usiness segment information.
Basis of Reporting	Basis of Reporting The condensed consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying condensed consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants.
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.
Derivative Assets and Liabilities	Derivative Assets and Liabilities Derivatives are recorded as either assets or liabilities on the Condensed Consolidated Balance Sheets measured at estimated fair value. The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and costs result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rate cases. The resulting regulatory assets associated with energy commodity derivative instruments are probable of recovery through future rates. Substantially all forward contracts to purchase or sell power and natural gas are recorded as derivative assets or liabilities at estimated fair value with an offsetting regulatory asset or liability. Contracts not considered derivatives are accounted for on the accrual basis until they are settled or realized unless there is a decline in the fair value of the contract determined to be other-than-temporary. 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 Condensed Consolidated Balance Sheets.
Fair Value Measurements	Fair Value Measurements Fair value represents the price that would be received when selling an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. Energy commodity derivative assets and liabilities, deferred compensation assets, some equity investments, as well as derivatives related to interest rate swaps and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 12 for the Company’s fair value disclosures.
Contingencies	Contingencies The Company has unresolved regulatory, legal and tax issues which have inherently uncertain outcomes. The Company accrues a loss contingency if it is probable a liability has been incurred and the amount of the loss or impairment can be reasonably estimated. The Company also discloses loss contingencies that do not meet these conditions for accrual if there is a reasonable possibility that a material loss may be incurred. See Note 16 for further discussion of the Company's commitments and contingencies.
Inventory	Inventories of materials and supplies, emission allowances, fuel stock and stored natural gas are recorded at average cost and consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Materials and supplies $ 80,916 $ 75,766 Emission allowances 40,842 — Stored natural gas 17,841 26,788 Fuel stock 5,575 5,120 Total $ 145,174 $ 107,674

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2023
Balance Sheet Related Disclosures [Abstract]
Schedule of Inventory	Inventories of materials and supplies, emission allowances, fuel stock and stored natural gas are recorded at average cost and consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Materials and supplies $ 80,916 $ 75,766 Emission allowances 40,842 — Stored natural gas 17,841 26,788 Fuel stock 5,575 5,120 Total $ 145,174 $ 107,674
Schedule of Other Current Assets	Other current assets consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Prepayments $ 51,194 $ 30,201 Income taxes receivable 32,157 30,740 Derivative assets net of collateral 1,981 18,198 Collateral posted for derivative instruments after netting with outstanding — 66,142 Other 8,257 5,886 Total $ 93,589 $ 151,167
Schedule of Net Utility Property Recorded at Original Cost Net of Accumulated Depreciation	Net utility property, which is recorded at original cost, net of accumulated depreciation, consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Utility plant in service $ 7,708,173 $ 7,561,688 Construction work in progress 199,365 164,147 Total 7,907,538 7,725,835 Less: Accumulated depreciation and amortization 2,282,470 2,281,126 Total $ 5,625,068 $ 5,444,709
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 September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Equity investments $ 154,873 $ 147,809 Operating lease ROU assets 68,087 68,238 Finance lease ROU assets 37,324 40,056 Non-utility property 30,909 25,401 Notes receivable 18,234 17,954 Long-term prepaid license fees 16,293 17,936 Pension asset 22,268 13,382 Investment in affiliated trust 11,547 11,547 Deferred compensation assets 7,763 7,541 Other 22,919 15,221 Total $ 390,217 $ 365,085
Other Current Liabilities	Other current liabilities consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, Accrued taxes other than income taxes $ 29,722 $ 38,568 Derivative liabilities 19,684 26,910 Employee paid time off accruals 31,231 29,279 Accrued interest 42,610 20,863 Deferred wholesale revenue — 8,481 Pensions and other postretirement benefits 14,327 15,625 Other 45,227 49,689 Total $ 182,801 $ 189,415
Schedule of Other Non-Current Liabilities and Deferred Credits	Other non-current liabilities and deferred credits consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, Operating lease liabilities $ 67,088 $ 64,284 Finance lease liabilities 39,945 42,495 Deferred investment tax credits 28,371 28,784 Climate Commitment Act obligations 30,457 — Asset retirement obligations 16,024 15,783 Derivative liabilities 14,035 7,892 Other 16,786 16,617 Total $ 212,706 $ 175,855
Schedule of Regulatory Assets and Liabilities	Regulatory assets and liabilities consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, 2023 December 31, 2022 Current Non-Current Current Non-Current Regulatory Assets Energy commodity derivatives $ 45,144 $ 13,715 $ 112,090 $ 18,185 Decoupling surcharge 2,087 3,407 6,250 5,449 Deferred natural gas costs 84,851 — 52,091 — Deferred power costs 34,751 17,766 23,356 24,043 Deferred income taxes — 242,498 — 240,325 Pension and other postretirement benefit plans — 131,269 — 135,337 Interest rate swaps — 181,050 — 185,919 AFUDC above FERC allowed rate — 49,778 — 51,649 Settlement with Coeur d'Alene Tribe — 36,972 — 37,809 Advanced meter infrastructure — 30,104 — 32,381 Utility plant abandoned — 30,362 — 24,389 Deferred Climate Commitment Act costs — 30,760 — — COVID-19 deferrals — 10,170 — 9,793 Unamortized debt repurchase costs — 5,817 — 6,177 Demand side management programs — 2,728 — 3,683 Other regulatory assets 1,094 68,703 — 58,189 Total regulatory assets $ 167,927 $ 855,099 $ 193,787 $ 833,328 Regulatory Liabilities Income tax related liabilities $ 41,680 $ 357,812 $ 73,267 $ 390,734 Deferred natural gas costs 6,599 — — — Deferred power costs — 3,712 — — Decoupling rebate 13,644 21,327 9,469 20,476 Utility plant retirement costs — 411,250 — 376,817 Interest rate swaps — 26,681 — 24,204 Deferred Climate Commitment Act revenues — 21,675 — — COVID-19 deferrals — 10,640 — 11,874 Other regulatory liabilities 11,920 10,620 12,929 16,732 Total regulatory liabilities $ 73,843 $ 863,717 $ 95,665 $ 840,837

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Schedule of Utilities Operating Revenue Expense Taxes	Utility-related taxes included in revenue from contracts with customers were as follows for the three and nine months ended September 30 (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Utility-related taxes $ 14,484 $ 14,049 $ 56,356 $ 51,091
Disaggregation of Revenue	Disaggregation of Total Operating Revenue The following table disaggregates total operating revenue by segment and source for the three and nine months ended September 30 (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Avista Utilities Revenue from contracts with customers $ 285,821 $ 276,988 $ 1,058,725 $ 970,247 Derivative revenues 77,562 76,248 141,080 218,024 Alternative revenue programs 3,578 ( 5,850 ) ( 9,947 ) ( 28,420 ) Deferrals and amortizations for rate refunds to customers 124 156 769 25 Other utility revenues 2,588 2,113 7,792 7,166 Total Avista Utilities 369,673 349,655 1,198,419 1,167,042 AEL&P Revenue from contracts with customers 9,700 9,526 34,934 32,747 Deferrals and amortizations for rate refunds to customers — ( 49 ) — ( 614 ) Other utility revenues 151 160 474 464 Total AEL&P 9,851 9,637 35,408 32,597 Other non-utility revenues 102 154 367 419 Total operating revenues $ 379,626 $ 359,446 $ 1,234,194 $ 1,200,058 Utility Revenue from Contracts with Customers by Type and Service The following table disaggregates revenue from contracts with customers associated with the Company's electric operations for the three and nine months ended September 30 (dollars in thousands): 2023 2022 Avista AEL&P Total Utility Avista AEL&P Total Utility Three months ended September 30: ELECTRIC OPERATIONS Revenue from contracts with customers Residential $ 95,881 $ 3,186 $ 99,067 $ 94,451 $ 3,123 $ 97,574 Commercial 89,772 6,447 96,219 89,411 6,339 95,750 Industrial 29,584 — 29,584 30,090 — 30,090 Public street and highway lighting 2,005 67 2,072 1,810 64 1,874 Total retail revenue 217,242 9,700 226,942 215,762 9,526 225,288 Transmission 7,721 — 7,721 9,662 — 9,662 Other revenue from contracts with 9,353 — 9,353 11,457 — 11,457 Total electric revenue from contracts $ 234,316 $ 9,700 $ 244,016 $ 236,881 $ 9,526 $ 246,407 Nine months ended September 30: ELECTRIC OPERATIONS Revenue from contracts with customers Residential $ 305,203 $ 14,485 $ 319,688 $ 299,562 $ 13,740 $ 313,302 Commercial 252,344 20,257 272,601 253,694 18,824 272,518 Industrial 82,707 — 82,707 82,235 — 82,235 Public street and highway lighting 5,940 192 6,132 5,586 183 5,769 Total retail revenue 646,194 34,934 681,128 641,077 32,747 673,824 Transmission 24,143 — 24,143 22,764 — 22,764 Other revenue from contracts with 33,580 — 33,580 27,628 — 27,628 Total electric revenue from contracts $ 703,917 $ 34,934 $ 738,851 $ 691,469 $ 32,747 $ 724,216 The following table disaggregates revenue from contracts with customers associated with the Company's natural gas operations for the three and nine months ended September 30 (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Avista Utilities Avista Utilities Avista Utilities Avista Utilities NATURAL GAS OPERATIONS Revenue from contracts with customers Residential $ 29,372 $ 22,960 $ 218,212 $ 174,655 Commercial 15,381 11,978 113,183 86,335 Industrial and interruptible 3,480 1,930 13,136 7,238 Total retail revenue 48,233 36,868 344,531 268,228 Transportation 1,866 1,832 6,058 6,331 Other revenue from contracts with customers 1,406 1,407 4,219 4,219 Total natural gas revenue from contracts with customers $ 51,505 $ 40,107 $ 354,808 $ 278,778

Derivatives and Risk Manageme_2

Derivatives and Risk Management (Tables)	9 Months Ended
	Sep. 30, 2023
Derivative Instruments and Hedges, Assets [Abstract]
Schedule of Energy Commodity Derivative Volumes	The following table presents the underlying energy commodity derivative volumes as of September 30, 2023 expected to be delivered or mature in the respective years shown (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical Financial Physical Financial Physical Financial Physical Financial Remainder 2023 5 — 12,377 33,810 74 267 735 5,295 2024 7 — 14,810 61,090 31 400 1,370 11,965 2025 — — 6,363 14,130 — 96 1,115 1,125 2026 — — 1,660 1,800 — — — — As of September 30, 2023 , there were no expected deliveries of energy commodity derivatives after 2 0 26. The following table presents the underlying energy commodity derivative volumes as of December 31, 2022 expected to be delivered or mature in the respective years shown (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical Financial Physical Financial Physical Financial Physical Financial 2023 5 — 19,140 79,253 136 1,011 4,145 29,473 2024 — — 533 30,658 — — 1,370 9,668 2025 — — 450 4,895 — — 1,115 1,125 As of December 31, 2022 , there were no expected deliveries of energy commodity derivatives after 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 outstanding as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Number of contracts 20 19 Notional amount (in United States dollars) $ 5,292 $ 8,563 Notional amount (in Canadian dollars) 7,159 11,659
Summary of Unsettled Interest Rate Swap Derivatives	The following table summarizes the unsettled interest rate swap derivatives outstanding as of September 30, 2023 and December 31, 2022 (dollars in thousands): Balance Sheet Date Number of Notional Mandatory September 30, 2023 2 $ 20,000 2024 1 $ 10,000 2025 December 31, 2022 4 $ 40,000 2023 1 10,000 2024
Schedules of Fair Values and Locations of Derivative Instruments	The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of September 30, 2023 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Gross Collateral Net Asset Foreign currency exchange derivatives Other current assets $ 23 $ — $ — $ 23 Interest rate swap derivatives Other property and investments-net and other non-current assets 6,379 — — 6,379 Energy commodity derivatives Other current assets 3,622 ( 1,664 ) — 1,958 Other property and investments-net and other non-current assets 534 ( 214 ) — 320 Other current liabilities 23,784 ( 70,886 ) 27,418 ( 19,684 ) Other non-current liabilities and deferred credits 4,378 ( 18,413 ) — ( 14,035 ) Total derivative instruments recorded on the balance sheet $ 38,720 $ ( 91,177 ) $ 27,418 $ ( 25,039 ) The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2022 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Gross Collateral Net Asset Foreign currency exchange derivatives Other current assets $ 43 $ — $ — $ 43 Other current liabilities — ( 3 ) — ( 3 ) Interest rate swap derivatives Other current assets 8,536 — — 8,536 Other property and investments-net and other non-current assets 2,648 — — 2,648 Other current liabilities — ( 52 ) — ( 52 ) Energy commodity derivatives Other current assets 32,257 ( 22,638 ) — 9,619 Other property and investments-net and other non-current assets 312 ( 16 ) — 296 Other current liabilities 107,902 ( 229,607 ) 94,850 ( 26,855 ) Other non-current liabilities and deferred credits 6,049 ( 24,530 ) 10,589 ( 7,892 ) Total derivative instruments recorded on the balance sheet $ 157,747 $ ( 276,846 ) $ 105,439 $ ( 13,660 )
Schedule of Collateral Outstanding Related to Derivative Instruments	The following table presents Avista Corp.'s collateral outstanding related to its derivative instruments as of September 30, 2023 and December 31, 2022 (in thousands): September 30, December 31, 2023 2022 Energy commodity derivatives Cash collateral posted $ 27,418 $ 171,581 Letters of credit outstanding 9,000 49,425 Balance sheet offsetting 27,418 105,439 No letters of credit or cash collateral were outstanding related to interest rate swap derivatives a s of September 30, 2023 and December 31, 2022. 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 in a liability position and the amount of additional collateral Avista Corp. could be required to post as of September 30, 2023 (in thousands): September 30, 2023 Interest rate swap derivatives Liabilities with credit-risk-related contingent features $ — Additional collateral to post — Energy commodity derivatives Liabilities with credit-risk-related contingent features 5,334 Additional collateral to post 3,996

Pension Plans and Other Postr_2

Pension Plans and Other Postretirement Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2023
Retirement Benefits, Description [Abstract]
Components of Net Periodic Benefit Cost	The Company uses a December 31 measurement date for its defined benefit pension and other postretirement benefit plans. The following table sets forth the components of net periodic benefit costs for the three and nine months ended September 30 (dollars in thousands): Pension Benefits Other Postretirement Benefits 2023 2022 2023 2022 Three months ended September 30: Service cost $ 3,098 $ 5,914 $ 559 $ 1,095 Interest cost 8,524 6,578 1,872 1,343 Expected return on plan assets ( 10,922 ) ( 10,950 ) ( 891 ) ( 700 ) Amortization of prior service cost (credit) 123 75 ( 263 ) ( 275 ) Net loss (gain) recognition 1,184 997 ( 54 ) 826 Net periodic benefit cost $ 2,007 $ 2,614 $ 1,223 $ 2,289 Nine months ended September 30: Service cost $ 11,092 $ 17,914 $ 1,909 $ 3,255 Interest cost 24,277 20,005 4,825 4,167 Expected return on plan assets ( 32,766 ) ( 32,851 ) ( 2,673 ) ( 2,100 ) Amortization of prior service cost (credit) 369 225 ( 789 ) ( 825 ) Net loss recognition 3,208 3,084 471 2,586 Net periodic benefit cost $ 6,180 $ 8,377 $ 3,743 $ 7,083

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Summary of Significant Factors Impact on Difference Between Effective Tax Rate and Federal Statutory Rate	The following table summarizes the significant factors impacting the difference between the Company's effective tax rate and the federal statutory rate for the three and nine months ended September 30 (dollars in thousands): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Federal income taxes at statutory rates $ 2,294 21.0 % $ ( 1,185 ) 21.0 % $ 14,872 21.0 % $ 13,764 21.0 % Increase (decrease) in tax resulting from: Flow through related to deduction of meters ( 3,744 ) ( 34.3 ) 1,192 ( 21.1 ) ( 22,956 ) ( 32.4 ) ( 18,643 ) ( 28.4 ) Tax effect of regulatory treatment of utility ( 828 ) ( 7.6 ) 420 ( 7.5 ) ( 6,040 ) ( 8.5 ) ( 6,878 ) ( 10.5 ) State income tax expense 151 1.4 ( 45 ) 0.8 949 1.3 856 1.3 Tax credits ( 862 ) ( 7.9 ) — — ( 1,997 ) ( 2.8 ) — — Settlement of prior year tax returns ( 867 ) ( 7.9 ) ( 318 ) 5.6 ( 867 ) ( 1.2 ) ( 318 ) ( 0.5 ) Uncertain tax positions 184 1.7 — — 184 0.2 — — Other ( 114 ) ( 1.0 ) 93 ( 1.6 ) ( 369 ) ( 0.5 ) ( 459 ) ( 0.7 ) Total income tax benefit $ ( 3,786 ) ( 34.6 )% $ 157 ( 2.8 )% $ ( 16,224 ) ( 22.9 )% $ ( 11,678 ) ( 17.8 )% (1) The Company's general rate cases included approval of base rate increases, offset by tax customer credits. As the tax customer credits are returned to customers, this results in a decrease to income tax expense as a result of flowing through the benefits related to meters and mixed service costs. The decrease in income tax expense offsets the increases in base rates granted to the Company in these general rate cases.

Short-Term Borrowings (Tables)

Short-Term Borrowings (Tables)	9 Months Ended
	Sep. 30, 2023
Avista Utilities [Member]
Line of Credit Facility [Line Items]
Schedule of Balances Outstanding and Interest Rates of Borrowings	Balances outstanding and interest rates on borrowings (excluding letters of credit) under Avista Corp.’s revolving committed line of credit were as follows as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, 2023 2022 Borrowings outstanding at end of period $ 220,000 $ 313,000 Letters of credit outstanding at end of period 4,638 35,563 Average interest rate on borrowings at end of period 6.42 % 5.31 %

Long-Term Debt to Affiliated _2

Long-Term Debt to Affiliated Trusts (Tables)	9 Months Ended
	Sep. 30, 2023
Long Term Debt To Affiliated Trust [Abstract]
Schedule of Distribution Rates	The distribution rates were as follows during the nine months ended September 30, 2023 and the year ended December 31, 2022: September 30, December 31, 2023 2022 Low distribution rate 5.64 % 1.05 % High distribution rate 6.55 % 5.64 % Distribution rate at the end of the period 6.55 % 5.64 %

Fair Value (Tables)

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2023
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 Condensed Consolidated Balance Sheets as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, 2023 December 31, 2022 Carrying Estimated Carrying Estimated Long-term debt (Level 2) $ 1,100,000 $ 886,339 $ 1,113,500 $ 966,881 Long-term debt (Level 3) 1,450,000 1,030,511 1,200,000 881,480 Snettisham finance lease obligation (Level 3) 43,304 38,200 45,730 41,700 Long-term debt to affiliated trusts (Level 3) 51,547 45,021 51,547 42,836
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 Condensed Consolidated Balance Sheets as of September 30, 2023 and December 31, 2022 at fair value on a recurring basis (dollars in thousands): Level 1 Level 2 Level 3 Counterparty Total September 30, 2023 Assets: Energy commodity derivatives $ — $ 32,318 $ — $ ( 30,040 ) $ 2,278 Foreign currency exchange derivatives — 23 — — 23 Interest rate swap derivatives — 6,379 — — 6,379 Equity Investments — — 50,477 — 50,477 Deferred compensation assets Mutual Funds: Fixed income securities (3) 1,119 — — — 1,119 Equity securities (3) 6,466 — — — 6,466 Total $ 7,585 $ 38,720 $ 50,477 $ ( 30,040 ) $ 66,742 Liabilities: Energy commodity derivatives (2) $ — $ 75,804 $ 15,373 $ ( 57,458 ) $ 33,719 Total $ — $ 75,804 $ 15,373 $ ( 57,458 ) $ 33,719 December 31, 2022 Assets: Energy commodity derivatives (2) $ — $ 146,232 $ 288 $ ( 136,605 ) $ 9,915 Foreign currency exchange derivatives — 43 — — 43 Interest rate swap derivatives — 11,184 — — 11,184 Equity Investments — — 54,284 — 54,284 Deferred compensation assets Mutual Funds: Fixed income securities (3) 1,267 — — — 1,267 Equity securities (3) 6,132 — — — 6,132 Total $ 7,399 $ 157,459 $ 54,572 $ ( 136,605 ) $ 82,825 Liabilities: Energy commodity derivatives (2) $ — $ 258,769 $ 18,022 $ ( 242,044 ) $ 34,747 Foreign currency exchange derivatives — 3 — — 3 Interest rate swap derivatives — 52 — — 52 Total $ — $ 258,824 $ 18,022 $ ( 242,044 ) $ 34,802 (1) The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties. (2) The Level 3 energy commodity derivative balances are associated with natural gas exchange agreements. (3) Included in other property and investments-net and other non-current assets on the Condensed 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 September 30, 2023 (dollars in thousands): Fair Value Valuation Unobservable Range and Weighted September 30, 2023 Technique Input Average Price Natural gas exchange agreement $ ( 15,373 ) Internally derived weighted average cost of gas Forward purchase prices $ 2.62 - $ 3.86 /mmBTU 3.30 Weighted Average Forward sales prices $ 3.22 - $ 11.65 /mmBTU 8.03 Weighted Average Purchase volumes 140,000 - 310,000 mmBTUs Sales volumes 75,000 - 310,000 mmBTUs The following table presents the quantitative information which was used to estimate the fair values of the Level 3 equity investments as of September 30, 2023 (dollars in thousands): Fair Value at September 30, 2023 Valuation Technique Unobservable Input Range Equity investments $ 50,477 Market approach Comparable enterprise values $ 130,000 -$ 388,600 246,000 Average Time to liquidity event 1 year Discounted cash flows Revenue market multiples 0.42 x to 5.47 x Revenue 1.76 x Average Market exit reduction 50 % Discount rate 25 % Annual revenues $ 6,000 - $ 265,000 Terminal date 2026
Schedule of Activity for Natural Gas Exchange Agreement Derivative Assets (Liabilities) Measured At Fair Value Using Significant Unobservable Inputs (Level 3)	The following table presents activity for assets and liabilities measured at fair value using significant unobservable inputs (Level 3) for the three and nine months ended September 30 (dollars in thousands): Natural Gas Exchange Agreement (1) Equity Investments Total Three Months Ended September 30, 2023: Beginning balance $ ( 11,721 ) $ 48,453 $ 36,732 Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities ( 3,652 ) — ( 3,652 ) Recognized in net income — 2,024 2,024 Ending balance as of September 30, 2023 $ ( 15,373 ) $ 50,477 $ 35,104 Three Months Ended September 30, 2022: Beginning balance $ ( 2,289 ) $ — $ ( 2,289 ) Transfers in (2) — 1,952 1,952 Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities ( 4,551 ) — ( 4,551 ) Recognized in net income — 3,829 3,829 Ending balance as of September 30, 2022 $ ( 6,840 ) $ 5,781 $ ( 1,059 ) Nine Months Ended September 30, 2023: Beginning balance $ ( 17,734 ) $ 54,284 $ 36,550 Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities 2,115 — 2,115 Recognized in net income — ( 3,174 ) ( 3,174 ) Purchases and debt conversions — 2,367 2,367 Settlements 246 — 246 Other — ( 3,000 ) ( 3,000 ) Ending balance as of September 30, 2023 $ ( 15,373 ) $ 50,477 $ 35,104 Nine Months Ended September 30, 2022: Beginning balance $ ( 7,771 ) $ — $ ( 7,771 ) Transfers in (2) — 1,952 1,952 Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities 3,144 — 3,144 Recognized in net income — 3,829 3,829 Settlements ( 2,213 ) — ( 2,213 ) Ending balance as of September 30, 2022 $ ( 6,840 ) $ 5,781 $ ( 1,059 ) (1) There were no purchases, issuances or transfers from other categories of any derivatives instruments during the periods presented in the table above. (2) The Company elected to measure certain equity investments at fair value on a recurring basis in 2022, as such the transfer in represents the value as of the election.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2023
Accumulated Other Comprehensive Loss [Abstract]
Schedule of Accumulated Other Comprehensive Loss, Net of Tax	Accumulated other comprehensive loss, net of tax, consisted of the following as of September 30, 2023 and December 31, 2022 (dollars in thousands): September 30, December 31, Unfunded benefit obligation for pensions and other postretirement benefit plans - 562 and $ 547 , respectively $ 2,114 $ 2,058
Reclassification out of Accumulated Other Comprehensive Loss	The following table details the reclassifications out of accumulated other comprehensive loss to net income by component for the three and nine months ended September 30 (dollars in thousands): Amounts Reclassified from Accumulated Other Three months ended September 30, Nine months ended September 30, Details about Accumulated Other Comprehensive Loss Components 2023 2022 2023 2022 Amortization of defined benefit pension and Amortization of net prior service cost (1) $ ( 140 ) $ ( 200 ) $ ( 420 ) $ ( 600 ) Amortization of net loss (1) 1,130 1,823 3,679 5,670 Adjustment due to effects of regulation (1) ( 1,014 ) ( 1,279 ) ( 3,330 ) ( 4,031 ) Total before tax (2) ( 24 ) 344 ( 71 ) 1,039 Tax expense (benefit) (2) 5 ( 72 ) 15 ( 218 ) Net of tax (2) $ ( 19 ) $ 272 $ ( 56 ) $ 821 (1) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details). (2) Description is also the affected line item on the Condensed Consolidated Statement of Income.

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2023
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 for the three and nine months ended September 30 (in thousands, except per share amounts): Three months ended September 30, Nine months ended September 30, 2023 2022 2023 2022 Numerator: Net income (loss) $ 14,716 $ ( 5,798 ) $ 87,045 $ 77,220 Denominator: Weighted-average number of common shares outstanding-basic 76,734 73,229 75,962 72,547 Effect of dilutive securities: Performance and restricted stock awards 27 69 94 82 Weighted-average number of common shares outstanding-diluted 76,761 73,298 76,056 72,629 Earnings (loss) per common share: Basic $ 0.19 $ ( 0.08 ) $ 1.15 $ 1.06 Diluted $ 0.19 $ ( 0.08 ) $ 1.14 $ 1.06

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Ownership and Operating Ownership Interest Percentage	Colstrip Units 3 and 4 are owned by the Company, PacifiCorp, Portland General Electric (PGE), and Puget Sound Energy (PSE) (collectively, the "Western Co-Owners"), as well as NorthWestern and Talen Montana, LLC (Talen), as tenants in common under an Ownership and Operating Agreement, dated May 6, 1981, as amended (O&O Agreement), in the percentages set forth below: Co-Owner Unit 3 Unit 4 Avista 15 % 15 % PacifiCorp 10 % 10 % PGE 20 % 20 % PSE 25 % 25 % NorthWestern — 30 % Talen 30 % —

Information by Business Segme_2

Information by Business Segments (Tables)	9 Months Ended
	Sep. 30, 2023
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 three months ended September 30, 2023: Operating revenues $ 369,673 $ 9,851 $ 379,524 $ 102 $ — $ 379,626 Resource costs 146,793 1,489 148,282 — — 148,282 Other operating expenses 98,609 3,860 102,469 603 — 103,072 Depreciation and amortization 64,125 2,735 66,860 45 — 66,905 Income (loss) from operations 37,081 1,552 38,633 ( 546 ) — 38,087 Interest expense (2) 33,896 1,456 35,352 538 ( 406 ) 35,484 Income tax expense (benefit) ( 3,845 ) 36 ( 3,809 ) 23 — ( 3,786 ) Net income 13,498 288 13,786 930 — 14,716 Capital expenditures (3) 127,666 4,865 132,531 — — 132,531 For the three months ended September 30, 2022: Operating revenues $ 349,655 $ 9,637 $ 359,292 $ 154 $ — $ 359,446 Resource costs 146,384 1,400 147,784 — — 147,784 Other operating expenses 98,062 3,639 101,701 1,041 — 102,742 Depreciation and amortization 60,780 2,704 63,484 32 — 63,516 Income (loss) from operations 18,660 1,661 20,321 ( 919 ) — 19,402 Interest expense (2) 28,214 1,489 29,703 243 ( 111 ) 29,835 Income tax expense (benefit) 197 21 218 ( 61 ) — 157 Net income (loss) ( 5,987 ) 228 ( 5,759 ) ( 39 ) — ( 5,798 ) Capital expenditures (3) 116,809 3,854 120,663 — — 120,663 For the nine months ended September 30 2023: Operating revenues $ 1,198,419 $ 35,408 $ 1,233,827 $ 367 $ — $ 1,234,194 Resource costs 478,947 3,507 482,454 — — 482,454 Other operating expenses 299,274 11,244 310,518 2,363 — 312,881 Depreciation and amortization 190,008 8,188 198,196 76 — 198,272 Income (loss) from operations 148,897 11,671 160,568 ( 2,072 ) — 158,496 Interest expense (2) 102,014 4,360 106,374 1,333 ( 942 ) 106,765 Income tax expense (benefit) ( 17,349 ) 2,048 ( 15,301 ) ( 923 ) — ( 16,224 ) Net income (loss) 83,935 5,689 89,624 ( 2,579 ) — 87,045 Capital expenditures (3) 347,264 12,013 359,277 — — 359,277 For the nine months ended September 30 2022: Operating revenues $ 1,167,042 $ 32,597 $ 1,199,639 $ 419 $ — $ 1,200,058 Resource costs 489,029 3,020 492,049 — — 492,049 Other operating expenses 289,828 10,882 300,710 4,907 — 305,617 Depreciation and amortization 180,765 8,102 188,867 94 — 188,961 Income (loss) from operations 121,476 9,760 131,236 ( 4,582 ) — 126,654 Interest expense (2) 81,864 4,463 86,327 508 ( 121 ) 86,714 Income tax expense (benefit) ( 14,728 ) 1,070 ( 13,658 ) 1,980 — ( 11,678 ) Net income 65,241 4,292 69,533 7,687 — 77,220 Capital expenditures (3) 324,123 7,186 331,309 756 — 332,065 Total Assets: As of September 30, 2023: $ 7,026,484 $ 271,192 $ 7,297,676 $ 190,853 $ ( 18,499 ) $ 7,470,030 As of December 31, 2022: $ 6,976,164 $ 264,322 $ 7,240,486 $ 187,027 $ ( 10,163 ) $ 7,417,350 (1) Intersegment eliminations reported as interest expense represent intercompany interest. (2) Including interest expense to affiliated trusts. (3) The capital expenditures for the other businesses are included in other investing activities on the Condensed Consolidated Statements of Cash Flows.

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Materials and supplies	$ 80,916	$ 75,766
Emission allowances	40,842
Stored natural gas	17,841	26,788
Fuel stock	5,575	5,120
Total	$ 145,174	$ 107,674

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Prepayments	$ 51,194	$ 30,201
Income taxes receivable	32,157	30,740
Derivative assets net of collateral	1,981	18,198
Collateral posted for derivative instruments after netting with outstanding derivative	0	66,142
Other	8,257	5,886
Total	$ 93,589	$ 151,167

Balance Sheet Components - Sc_3

Balance Sheet Components - Schedule of Net Utility Property Recorded at Original Cost Net of Accumulated Depreciation (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Utility plant in service	$ 7,708,173	$ 7,561,688
Construction work in progress	199,365	164,147
Total	7,907,538	7,725,835
Less: Accumulated depreciation and amortization	2,282,470	2,281,126
Total	$ 5,625,068	$ 5,444,709

Balance Sheet Components - Othe

Balance Sheet Components - Other Property and Investments-Net and Other Non-current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Equity investments	$ 154,873	$ 147,809
Operating lease ROU assets	$ 68,087	$ 68,238
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Total	Total
Finance lease ROU assets	$ 37,324	$ 40,056
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Total	Total
Non-utility property	$ 30,909	$ 25,401
Notes receivable	18,234	17,954
Long-term prepaid license fees	16,293	17,936
Pension asset	22,268	13,382
Investment in affiliated trust	11,547	11,547
Deferred compensation assets	7,763	7,541
Other	22,919	15,221
Total	$ 390,217	$ 365,085

Balance Sheet Components - Ot_2

Balance Sheet Components - Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Accrued taxes other than income taxes	$ 29,722	$ 38,568
Derivative liabilities	19,684	26,910
Employee paid time off accruals	31,231	29,279
Accrued interest	42,610	20,863
Deferred wholesale revenue		8,481
Pensions and other postretirement benefits	14,327	15,625
Other	45,227	49,689
Total	$ 182,801	$ 189,415

Balance Sheet Components - Sc_4

Balance Sheet Components - Schedule of Other Non-Current Liabilities and Deferred Credits (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Operating lease liabilities	$ 67,088	$ 64,284
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Total	Total
Finance lease liabilities	$ 39,945	$ 42,495
Deferred investment tax credits	28,371	28,784
Climate Commitment Act Obligations	30,457
Asset retirement obligations	16,024	15,783
Derivative liabilities	14,035	7,892
Other	16,786	16,617
Total	$ 212,706	$ 175,855

Balance Sheet Components - Sc_5

Balance Sheet Components - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	$ 167,927	$ 193,787
Regulatory Assets, Non-Current	855,099	833,328
Regulatory Liabilities, Current	73,843	95,665
Regulatory Liabilities, Non-Current	863,717	840,837
Income Tax Related Liabilities [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Current	41,680	73,267
Regulatory Liabilities, Non-Current	357,812	390,734
Deferred Natural Gas Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Current	6,599	0
Regulatory Liabilities, Non-Current	0	0
Deferred power costs
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Non-Current	3,712
Decoupling Rebate [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Current	13,644	9,469
Regulatory Liabilities, Non-Current	21,327	20,476
Utility Plant Retirement Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Current	0	0
Regulatory Liabilities, Non-Current	411,250	376,817
Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Current	0	0
Regulatory Liabilities, Non-Current	26,681	24,204
Deferred Climate Commitment Act Revenues [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Non-Current	21,675
COVID-19 Deferrals [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Current	0	0
Regulatory Liabilities, Non-Current	10,640	11,874
Other Regulatory Liabilities [Member]
Regulated Asset Liability [Line Items]
Regulatory Liabilities, Current	11,920	12,929
Regulatory Liabilities, Non-Current	10,620	16,732
Energy Commodity Derivatives [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	45,144	112,090
Regulatory Assets, Non-Current	13,715	18,185
Decoupling Surcharge [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	2,087	6,250
Regulatory Assets, Non-Current	3,407	5,449
Deferred Natural Gas Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	84,851	52,091
Regulatory Assets, Non-Current	0	0
Deferred Power Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	34,751	23,356
Regulatory Assets, Non-Current	17,766	24,043
Deferred Income Taxes [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	242,498	240,325
Pension and Other Postretirement Benefit Plans [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	131,269	135,337
Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	181,050	185,919
AFUDC Above FERC Allowed Rate [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	49,778	51,649
Settlement with Coeur d'Alene Tribe [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	36,972	37,809
Advanced Meter Infrastructure [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	30,104	32,381
Utility Plant Abandoned [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	30,362	24,389
Deferred Climate Commitment Act Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	30,760	0
COVID-19 Deferrals [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	10,170	9,793
Unamortized Debt Repurchase Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	5,817	6,177
Demand Side Management Programs [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	2,728	3,683
Other Regulatory Assets [Member]
Regulated Asset Liability [Line Items]
Regulatory Assets, Current	0	0
Regulatory Assets, Non-Current	$ 68,703	$ 58,189

Revenue - Schedule of Utilities

Revenue - Schedule of Utilities Operating Revenue Expense Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenue from Contract with Customer [Abstract]
Utility-related taxes	$ 14,484	$ 14,049	$ 56,356	$ 51,091

Revenue - Additional Informatio

Revenue - Additional Information (Details) $ in Millions	Sep. 30, 2023 USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 8.7

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 379,626	$ 359,446	$ 1,234,194	$ 1,200,058
Alternative revenue programs	3,578	(5,850)	(9,947)	(28,420)
Total utility revenues	379,524	359,292	1,233,827	1,199,639
Unregulated Operating Revenue	102	154	367	419
Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	99,067	97,574	319,688	313,302
Commercial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	96,219	95,750	272,601	272,518
Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	29,584	30,090	82,707	82,235
Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	2,072	1,874	6,132	5,769
Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	226,942	225,288	681,128	673,824
Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	7,721	9,662	24,143	22,764
Other Electric Revenues from Contracts With Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	9,353	11,457	33,580	27,628
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	244,016	246,407	738,851	724,216
Avista Utilities [Member]
Disaggregation of Revenue [Line Items]
Derivative revenues	77,562	76,248	141,080	218,024
Alternative revenue programs	3,578	(5,850)	(9,947)	(28,420)
Deferrals and amortizations for rate refunds to customers	124	156	769	25
Other utility revenues	2,588	2,113	7,792	7,166
Total utility revenues	369,673	349,655	1,198,419	1,167,042
Revenue from contract with customer including assessed tax	285,821	276,988	1,058,725	970,247
Avista Utilities [Member] | Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	95,881	94,451	305,203	299,562
Avista Utilities [Member] | Commercial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	89,772	89,411	252,344	253,694
Avista Utilities [Member] | Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	29,584	30,090	82,707	82,235
Avista Utilities [Member] | Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	2,005	1,810	5,940	5,586
Avista Utilities [Member] | Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	217,242	215,762	646,194	641,077
Avista Utilities [Member] | Transmission Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	7,721	9,662	24,143	22,764
Avista Utilities [Member] | Other Electric Revenues from Contracts With Customers [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	9,353	11,457	33,580	27,628
Avista Utilities [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	234,316	236,881	703,917	691,469
Avista Utilities [Member] | Residential Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	29,372	22,960	218,212	174,655
Avista Utilities [Member] | Commercial Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	15,381	11,978	113,183	86,335
Avista Utilities [Member] | Industrial and Interruptible Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	3,480	1,930	13,136	7,238
Avista Utilities [Member] | Retail Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	48,233	36,868	344,531	268,228
Avista Utilities [Member] | Transportation Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	1,866	1,832	6,058	6,331
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	1,406	1,407	4,219	4,219
Avista Utilities [Member] | Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customer including assessed tax	51,505	40,107	354,808	278,778
Alaska Electric Light & Power [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9,700	9,526	34,934	32,747
Deferrals and amortizations for rate refunds to customers		(49)		(614)
Other utility revenues	151	160	474	464
Total utility revenues	9,851	9,637	35,408	32,597
Alaska Electric Light & Power [Member] | Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,186	3,123	14,485	13,740
Alaska Electric Light & Power [Member] | Commercial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6,447	6,339	20,257	18,824
Alaska Electric Light & Power [Member] | Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	67	64	192	183
Alaska Electric Light & Power [Member] | Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9,700	9,526	34,934	32,747
Alaska Electric Light & Power [Member] | Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	9,700	9,526	34,934	32,747
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Unregulated Operating Revenue	$ 102	$ 154	$ 367	$ 419

Leases - Additional Information

Leases - Additional Information (Details)	9 Months Ended
	Sep. 30, 2023 MW
Lancaster Power Purchase Agreement [Member]
Lessee, Lease, Description [Line Items]
Evaluated Power Capacity	270

Derivatives and Risk Manageme_3

Derivatives and Risk Management - Schedule of Energy Commodity Derivative Volumes (Details) MWh in Thousands, MMBTU in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023 MMBTU MWh	Dec. 31, 2022 MMBTU MWh
Purchase [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MWh	5	5
Year two | MWh	0	0
Year three | MWh	0	0
Year four | MWh	0
Purchase [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MMBTU	12,377	19,140
Year two | MMBTU	14,810	533
Year three | MMBTU	6,363	450
Year four | MMBTU	1,660
Purchase [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MWh	0	0
Year two | MWh	0	0
Year three | MWh	0	0
Year four | MWh	0
Purchase [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MMBTU	33,810	79,253
Year two | MMBTU	61,090	30,658
Year three | MMBTU	14,130	4,895
Year four | MMBTU	1,800
Sales [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MWh	74	136
Year two | MWh	31	0
Year three | MWh	0	0
Year four | MWh	0
Sales [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MMBTU	735	4,145
Year two | MMBTU	1,370	1,370
Year three | MMBTU	1,115	1,115
Year four | MMBTU	0
Sales [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MWh	267	1,011
Year two | MWh	400	0
Year three | MWh	96	0
Year four | MWh	0
Sales [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
Year one | MMBTU	5,295	29,473
Year two | MMBTU	11,965	9,668
Year three | MMBTU	1,125	1,125
Year four | MMBTU	0

Derivatives and Risk Manageme_4

Derivatives and Risk Management - Additional Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2023 USD ($) MMBTU MWh	Dec. 31, 2022 USD ($) MMBTU MWh
Canadian [Member]
Derivative [Line Items]
Number of days Canadian currency prices are settled with U.S. dollars	60 days
Interest Rate Swap [Member]
Derivative [Line Items]
Cash collateral posted | $	$ 0	$ 0
Letters of credit outstanding | $	$ 0	$ 0
Purchase [Member] | Physical [Member] | Electric Derivative [Member]
Derivative [Line Items]
Expected deliveries of energy commodity derivatives after four 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 four 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 four 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 four 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 four 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 four 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 four 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 four 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	Sep. 30, 2023 USD ($) DerivativeContracts	Sep. 30, 2023 CAD ($) DerivativeContracts	Dec. 31, 2022 USD ($) DerivativeContracts	Dec. 31, 2022 CAD ($) DerivativeContracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Number of contracts | DerivativeContracts	20	20	19	19
United States of America, Dollars [Member] | Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Notional amount	$ 5,292		$ 8,563
Canada, Dollars [Member] | Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Notional amount		$ 7,159		$ 11,659

Derivatives and Risk Manageme_6

Derivatives and Risk Management - Summary of Unsettled Interest Rate Swap Derivatives (Details) - Interest Rate Swap [Member] $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023 USD ($) Contract	Dec. 31, 2022 USD ($) Contract
2023 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts | Contract		4
Notional Amount | $		$ 40,000
Mandatory Cash Settlement Date		2023
2024 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts | Contract	2	1
Notional Amount | $	$ 20,000	$ 10,000
Mandatory Cash Settlement Date	2024	2024
2025 [Member]
Derivatives, Fair Value [Line Items]
Number of Contracts | Contract	1
Notional Amount | $	$ 10,000
Mandatory Cash Settlement Date	2025

Derivatives and Risk Manageme_7

Derivatives and Risk Management - Schedules of Fair Values and Locations of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Gross Asset	$ 38,720	$ 157,747
Gross Liability	(91,177)	(276,846)
Collateral Netted	27,418	105,439
Net Asset (Liability) on Balance Sheet	(25,039)	(13,660)
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	27,418	105,439
Other Current Liabilities [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Liability		(3)
Net Asset (Liability) on Balance Sheet		(3)
Other Current Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Liability		(52)
Net Asset (Liability) on Balance Sheet		(52)
Other Current Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	23,784	107,902
Gross Liability	(70,886)	(229,607)
Collateral Netted	27,418	94,850
Net Asset (Liability) on Balance Sheet	(19,684)	(26,855)
Other Current Assets [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	23	43
Net Asset (Liability) on Balance Sheet	23	43
Other Current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		8,536
Net Asset (Liability) on Balance Sheet		8,536
Other Current Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	3,622	32,257
Gross Liability	(1,664)	(22,638)
Net Asset (Liability) on Balance Sheet	1,958	9,619
Other Property and Investments Net and Other Non-current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	6,379	2,648
Net Asset (Liability) on Balance Sheet	6,379	2,648
Other Property and Investments Net and Other Non-current Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	534	312
Gross Liability	(214)	(16)
Net Asset (Liability) on Balance Sheet	320	296
Other Noncurrent Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	4,378	6,049
Gross Liability	(18,413)	(24,530)
Collateral Netted		10,589
Net Asset (Liability) on Balance Sheet	$ (14,035)	$ (7,892)

Derivatives and Risk Manageme_8

Derivatives and Risk Management - Schedule of Collateral Outstanding Related to Derivative Instruments (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Derivative [Line Items]
Balance sheet offsetting	$ 27,418,000	$ 105,439,000
Commodity Contracts [Member]
Derivative [Line Items]
Cash collateral posted	27,418,000	171,581,000
Letters of credit outstanding	9,000,000	49,425,000
Balance sheet offsetting	27,418,000	105,439,000
Liabilities with credit-risk-related contingent features	5,334,000
Additional collateral to post	3,996,000
Interest Rate Swap [Member]
Derivative [Line Items]
Cash collateral posted	0	0
Letters of credit outstanding	0	$ 0
Liabilities with credit-risk-related contingent features	0
Additional collateral to post	$ 0

Pension Plans and Other Postr_3

Pension Plans and Other Postretirement Benefit Plans - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Payment for pension benefits	$ 10,000,000	$ 42,000,000
Percentage of service related net periodic benefit costs capitalized to utility property	40%
Percentage of service related net periodic benefit costs recorded to operating expenses	60%
Percentage of non-service related net periodic benefit costs capitalized to regulatory assets	40%
Percentage of non-service related net periodic benefit costs recorded to other expense	60%
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to pension plan	$ 0

Pension Plans and Other Postr_4

Pension Plans and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3,098	$ 5,914	$ 11,092	$ 17,914
Interest cost	8,524	6,578	24,277	20,005
Expected return on plan assets	(10,922)	(10,950)	(32,766)	(32,851)
Amortization of prior service cost (credit)	123	75	369	225
Net loss (gain) recognition	1,184	997	3,208	3,084
Net periodic benefit cost	2,007	2,614	6,180	8,377
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	559	1,095	1,909	3,255
Interest cost	1,872	1,343	4,825	4,167
Expected return on plan assets	(891)	(700)	(2,673)	(2,100)
Amortization of prior service cost (credit)	(263)	(275)	(789)	(825)
Net loss (gain) recognition	(54)	826	471	2,586
Net periodic benefit cost	$ 1,223	$ 2,289	$ 3,743	$ 7,083

Income Taxes - Summary of Signi

Income Taxes - Summary of Significant Factors Impact on Difference Between Effective Tax Rate and Federal Statutory Rate (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Federal income taxes at statutory rates	$ 2,294	$ (1,185)	$ 14,872	$ 13,764
Flow through related to deduction of meters and mixed service costs	(3,744)	1,192	(22,956)	(18,643)
Tax effect of regulatory treatment of utility plant differences	(828)	420	(6,040)	(6,878)
State income tax expense	151	(45)	949	856
Tax credits	(862)		(1,997)
Settlement of prior year tax returns	(867)	(318)	(867)	(318)
Uncertain tax positions	184		184
Other	(114)	93	(369)	(459)
Total income tax benefit	$ (3,786)	$ 157	$ (16,224)	$ (11,678)
Federal income taxes at statutory rates	21%	21%	21%	21%
Flow through related to deduction of meters and mixed service costs	(34.30%)	(21.10%)	(32.40%)	(28.40%)
Tax effect of regulatory treatment of utility plant differences	(7.60%)	(7.50%)	(8.50%)	(10.50%)
State income tax expense	1.40%	0.80%	1.30%	1.30%
Tax credits	(7.90%)		(2.80%)
Settlement of prior year tax returns	(7.90%)	5.60%	(1.20%)	(0.50%)
Uncertain tax positions	1.70%		0.20%
Other	(1.00%)	(1.60%)	(0.50%)	(0.70%)
Total income tax benefit	(34.60%)	(2.80%)	(22.90%)	(17.80%)

Short-Term Borrowings - Additio

Short-Term Borrowings - Additional Information (Details) - USD ($)	1 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2021	Sep. 30, 2023	Dec. 31, 2022	Mar. 31, 2023	Apr. 30, 2014
Short-term Debt [Line Items]
Line of credit, outstanding			$ 0
Avista Utilities [Member]
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity		$ 500,000,000			$ 400,000,000
Line of credit facility, expiration date	2028-06
Line of credit facility additional expiration period		2 years
Bearing interest rate		12%
Credit agreement amount borrowed				$ 150,000,000
Letters of credit outstanding		$ 4,638,000	35,563,000
Line of credit facility, covenant terms, maximum debt to equity ratio		65%
Avista Utilities [Member] | Revolving credit agreement [Member]
Short-term Debt [Line Items]
Line of credit facility, termination date		2023-06
Current borrowings			100,000,000
Avista Utilities [Member] | 2022 Term Loan [Member]
Short-term Debt [Line Items]
Principal amount			$ 150,000,000
Maturity date			Mar. 30, 2023
Avista Utilities [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Principal amount			$ 50,000,000
Letters of credit outstanding		$ 9,000,000	18,500,000
Alaska Electric Light & Power [Member]
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity		$ 25,000,000
Line of credit facility, expiration date		2028-06
Line of credit, outstanding		$ 1,500,000	$ 0

Short-Term Borrowings - Schedul

Short-Term Borrowings - Schedule of Balances Outstanding and Interest Rates of Borrowings (Details) - Avista Utilities [Member] - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Borrowings outstanding at end of period	$ 220,000	$ 313,000
Letters of credit outstanding at end of period	$ 4,638	$ 35,563
Average interest rate on borrowings at end of period	6.42%	5.31%

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details) $ in Thousands	1 Months Ended	9 Months Ended
	Mar. 31, 2023 USD ($) Contract	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt		$ 250,000	$ 399,856
Repayments of short-term debt		$ 150,000
5.66% Due in 2053 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt	$ 250,000
Debt instrument interest rate percentage	5.66%
Debt instrument maturity year	2053
5.66% Due in 2053 [Member] | Interest Rate Swap [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Number of interest rate swaps settled | Contract	4
Notional amount	$ 40,000
Net payments from settlement of derivatives	$ 7,500

Long-Term Debt to Affiliated _3

Long-Term Debt to Affiliated Trusts - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended	12 Months Ended
	Jul. 31, 2023	Sep. 30, 2023	Dec. 31, 2000
Debt Instrument [Line Items]
Payments for repurchase of trust preferred securities			$ 10
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
Avista Corp [Member]
Debt Instrument [Line Items]
Noncontrolling interest, ownership percentage by parent		100%
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%
Trust Preferred Securities Subject to Mandatory Redemption [Member] | 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] | SOFR [Member] | Avista Capital II [Member]
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	1.137%
Debt instrument basis tenor spread adjustment rate	0.26%
Common Trust Securities [Member] | 1997 Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B [Member] | Avista Capital II [Member]
Debt Instrument [Line Items]
Principal amount		$ 1.5

Long-Term Debt to Affiliated _4

Long-Term Debt to Affiliated Trusts - Schedule of Distribution Rates Paid (Details) - Trust Preferred Securities Subject to Mandatory Redemption [Member]	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Interest rate	6.55%	5.64%
Minimum [Member]
Debt Instrument [Line Items]
Interest rate	5.64%	1.05%
Maximum [Member]
Debt Instrument [Line Items]
Interest rate	6.55%	5.64%

Fair Value - Schedule of Carryi

Fair Value - Schedule of Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Level 2 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 1,100,000	$ 1,113,500
Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	886,339	966,881
Level 3 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,450,000	1,200,000
Level 3 [Member] | Reported Value Measurement [Member] | Alaska Electric Light & Power [Member] | Finance Lease [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease Obligation	43,304	45,730
Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,030,511	881,480
Level 3 [Member] | Estimate of Fair Value Measurement [Member] | Alaska Electric Light & Power [Member] | Finance Lease [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Finance Lease Obligation	38,200	41,700
Affiliated Entity [Member] | Level 3 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	51,547	51,547
Affiliated Entity [Member] | Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 45,021	$ 42,836

Fair Value - Additional Informa

Fair Value - Additional Information (Details)	Sep. 30, 2023 Investment
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of equity investments measured at fair value on recurring basic	2
Measurement Input, Quoted Price [Member] | Secured and Unsecured Debt [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, measurement input	1
Measurement Input, Quoted Price [Member] | Minimum [Member] | Secured and Unsecured Debt [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, measurement input	0.5444
Measurement Input, Quoted Price [Member] | Maximum [Member] | Secured and Unsecured Debt [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, measurement input	1.0008

Fair Value - Schedule of Fair V

Fair Value - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands		Sep. 30, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		$ 38,720	$ 157,747
Liability		91,177	276,846
Fair Value, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		66,742	82,825
Financial Liabilities Fair Value Disclosure		33,719	34,802
Counterparty and Cash Collateral Netting, Assets	[1]	(30,040)	(136,605)
Counterparty and Cash Collateral Netting, Liabilities	[1]	(57,458)	(242,044)
Fair Value, Recurring [Member] | Fixed Income Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	[2]	1,119	1,267
Fair Value, Recurring [Member] | Equity Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity investments		50,477	54,284
Deferred compensation assets:	[2]	6,466	6,132
Fair Value, Recurring [Member] | Energy Commodity Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and Cash Collateral Netting, Assets	[1]	(30,040)	(136,605)	[3]
Derivative Asset		2,278	9,915	[3]
Counterparty and Cash Collateral Netting, Liabilities	[1],[3]	(57,458)	(242,044)
Derivative Liability	[3]	33,719	34,747
Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset		6,379	11,184
Derivative Liability			$ 52
Fair Value, Recurring [Member] | Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Liability		$ 15,373
Fair Value, Recurring [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Investments and Other Noncurrent Assets	Investments and Other Noncurrent Assets
Derivative Liability, Statement of Financial Position [Extensible Enumeration]			Other Liabilities, Noncurrent
Derivative Asset		$ 23	$ 43
Derivative Liability			3
Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		7,585	7,399
Fair Value, Recurring [Member] | Level 1 [Member] | Fixed Income Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	[2]	1,119	1,267
Fair Value, Recurring [Member] | Level 1 [Member] | Equity Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	[2]	6,466	6,132
Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		38,720	157,459
Financial Liabilities Fair Value Disclosure		75,804	258,824
Fair Value, Recurring [Member] | Level 2 [Member] | Energy Commodity Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		32,318	146,232	[3]
Liability	[3]	75,804	258,769
Fair Value, Recurring [Member] | Level 2 [Member] | Interest Rate Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		6,379	11,184
Liability			52
Fair Value, Recurring [Member] | Level 2 [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset		23	43
Liability			3
Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure		50,477	54,572
Financial Liabilities Fair Value Disclosure		15,373	18,022
Fair Value, Recurring [Member] | Level 3 [Member] | Equity Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity investments		50,477	54,284
Fair Value, Recurring [Member] | Level 3 [Member] | Energy Commodity Derivatives [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	[3]		288
Liability	[3]	$ 15,373	$ 18,022
[1] The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties. Included in other property and investments-net and other non-current assets on the Condensed Consolidated Balance Sheets. The Level 3 energy commodity derivative balances are associated with natural gas exchange agreements.

Fair Value - Schedule of Quanti

Fair Value - Schedule of Quantitative Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2023 USD ($) MMBTU $ / MMBTU	Dec. 31, 2022 USD ($)
Fair Value, Recurring [Member] | Equity Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments	$ 50,477	$ 54,284
Fair Value, Recurring [Member] | Equity Investments [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments	$ 50,477	$ 54,284
Fair Value, Recurring [Member] | Discounted Cash Flows [Member] | Equity Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, terminal date	2026
Fair Value, Recurring [Member] | Discounted Cash Flows [Member] | Equity Investments [Member] | Discount Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	25
Fair Value, Recurring [Member] | Discounted Cash Flows [Member] | Equity Investments [Member] | Market Exit Reduction [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	50
Fair Value, Recurring [Member] | Minimum [Member] | Market Approach [Member] | Equity Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, comparable enterprise values	$ 130,000
Equity investments, time to liquidity event	1 year
Fair Value, Recurring [Member] | Minimum [Member] | Discounted Cash Flows [Member] | Equity Investments [Member] | Annual Revenues [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, annual revenues	$ 6,000
Fair Value, Recurring [Member] | Minimum [Member] | Discounted Cash Flows [Member] | Equity Investments [Member] | Revenue Market Multiples [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	0.42
Fair Value, Recurring [Member] | Maximum [Member] | Market Approach [Member] | Equity Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, comparable enterprise values	$ 388,600
Fair Value, Recurring [Member] | Maximum [Member] | Discounted Cash Flows [Member] | Equity Investments [Member] | Annual Revenues [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, annual revenues	$ 265,000
Fair Value, Recurring [Member] | Maximum [Member] | Discounted Cash Flows [Member] | Equity Investments [Member] | Revenue Market Multiples [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	5.47
Fair Value, Recurring [Member] | Weighted Average [Member] | Market Approach [Member] | Equity Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, comparable enterprise values	$ 246,000
Fair Value, Recurring [Member] | Weighted Average [Member] | Discounted Cash Flows [Member] | Equity Investments [Member] | Revenue Market Multiples [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Equity investments, measurement input	1.76
Natural Gas Exchange Agreements [Member] | 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 | $ / MMBTU	2.62
Transaction/Delivery Volumes | MMBTU	140,000
Natural Gas Exchange Agreements [Member] | 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 | $ / MMBTU	3.86
Transaction/Delivery Volumes | MMBTU	310,000
Natural Gas Exchange Agreements [Member] | 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 | $ / MMBTU	3.3
Natural Gas Exchange Agreements [Member] | 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 | $ / MMBTU	3.22
Transaction/Delivery Volumes | MMBTU	75,000
Natural Gas Exchange Agreements [Member] | 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 | $ / MMBTU	11.65
Transaction/Delivery Volumes | MMBTU	310,000
Natural Gas Exchange Agreements [Member] | 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 | $ / MMBTU	8.03
Natural Gas Exchange Agreements [Member] | Fair Value, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Derivative Liability	$ (15,373)

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) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)
Level 3 [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 36,732	$ (2,289)	$ 36,550	$ (7,771)
Transfers in		1,952		1,952
Included in regulatory assets/liabilities	(3,652)	(4,551)	2,115	3,144
Recognized in net income	2,024	3,829	(3,174)	3,829
Purchases			2,367
Settlements			246	(2,213)
Other			(3,000)
Ending Balance	35,104	(1,059)	35,104	(1,059)
Natural Gas Exchange Agreements [Member] | Level 3 [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(11,721)	(2,289)	(17,734)	(7,771)
Included in regulatory assets/liabilities	(3,652)	(4,551)	2,115	3,144
Settlements			246	(2,213)
Ending Balance	(15,373)	(6,840)	(15,373)	(6,840)
Equity Investment [Member] | Level 3 [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	48,453		54,284
Transfers in		1,952		1,952
Recognized in net income	2,024	3,829	(3,174)	3,829
Purchases and debt conversions			2,367
Other			(3,000)
Ending Balance	$ 50,477	$ 5,781	$ 50,477	$ 5,781

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Class Of Stock [Line Items]
Proceeds from issuance of common stock	$ 28,600		$ 88,165	$ 92,966
Common stock, shares authorized	200,000,000		200,000,000		200,000,000
Common Stock [Member]
Class Of Stock [Line Items]
Shares issued under sales agency agreements	839,941	798,722	2,418,177	2,277,281
Sales Agency Agreement [Member] | Common Stock [Member]
Class Of Stock [Line Items]
Shares issued under sales agency agreements	800,000		2,300,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss, Net of Tax (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Loss [Abstract]
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $557 and $547, respectively	$ 2,114	$ 2,058

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss - Schedule of Accumulated Other Comprehensive Loss, Net of Tax (Parenthetical) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Loss [Abstract]
Accumulated other comprehensive income (loss), pension and other postretirement benefit plans net unamortized (gain) loss, tax	$ 562	$ 547

Accumulated Other Comprehensi_5

Accumulated Other Comprehensive Loss - Reclassification out of Accumulated Other Comprehensive Loss (Details) - Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Amortization of net prior service cost	$ (140)	$ (200)	$ (420)	$ (600)
Amortization of net loss	1,130	1,823	3,679	5,670
Adjustment due to effects of regulation	(1,014)	(1,279)	(3,330)	(4,031)
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, before tax	(24)	344	(71)	1,039
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, tax	5	(72)	15	(218)
Other comprehensive (income) loss, defined benefit plan, reclassification adjustment from AOCI, after tax	$ (19)	$ 272	$ (56)	$ 821

Earnings Per Common Share - Sch

Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Numerator:
Net income (loss)	$ 14,716	$ (5,798)	$ 87,045	$ 77,220
Denominator:
Weighted-average number of common shares outstanding-basic	76,734	73,229	75,962	72,547
Effect of dilutive securities:
Performance and restricted stock awards	27	69	94	82
Weighted-average number of common shares outstanding-diluted	76,761	73,298	76,056	72,629
Earnings (loss) per common share:
Basic	$ 0.19	$ (0.08)	$ 1.15	$ 1.06
Diluted	$ 0.19	$ (0.08)	$ 1.14	$ 1.06

Earnings Per Common Share - Add

Earnings Per Common Share - Additional Information (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share, amount	0	0	0	0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)		1 Months Ended			9 Months Ended
	Sep. 01, 2023 Lawsuit	Apr. 30, 2022 USD ($) a	Jul. 31, 2021 USD ($)	Aug. 31, 2019 USD ($)	Sep. 30, 2023 USD ($) Lawsuit Plaintiff	Aug. 29, 2023 a Building	Aug. 18, 2023 a Building	Sep. 30, 2022	May 31, 2021 a Building
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
Road 11 Fire [Member] | Damage from Fire [Member] | Avista Corp [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value		$ 5,000,000
Road fire covered area | a		10,000
Babb Road Fire [Member] | Damage from Fire [Member]
Loss Contingencies [Line Items]
Loss contingency, damages sought, value					$ 23,000,000
Number of residential, commercial and other structures impacted | Building									220
Road fire covered area | a									15,000
Number of lawsuit filed by an individual | Lawsuit	2
Number of lawsuit filed by a business entity | Lawsuit	1
Number of subrogation actions filed | Lawsuit					6
Number of actions on behalf of individual plaintiffs | Plaintiff					4
Number of class action lawsuit | Lawsuit					1
August Fire Activity [Member] | Damage from Fire [Member]
Loss Contingencies [Line Items]
Number of residential, commercial and other structures impacted | Building						6	240
Road fire covered area | a						53
August Fire Activity [Member] | Damage from Fire [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Road fire covered area | a							10,000
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					NorthWestern has initiated arbitration pursuant to the O&O Agreement to resolve these business disagreements, and two actions have been initiated to compel arbitration of those disputes: one by Talen in the Montana Thirteenth Judicial District Court for Yellowstone County, and one by the Western Co-Owners, which is pending in Montana Federal District Court. In light of the ownership transfer agreements discussed below, the Colstrip owners agreed to stay both the litigation and the arbitration through January 12, 2024, at which time the proceedings would resume absent further agreement between the owners.
Colstrip [Member] | PSE [Member] | Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest					25%			25%

Commitments and Contingencies_2

Commitments and Contingencies - Ownership and Operating Interest Percentage (Details) - Colstrip [Member]	Sep. 30, 2023	Jan. 16, 2023	Sep. 30, 2022
Avista [Member] | Unit 3 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	15%
Avista [Member] | Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	15%
PacifiCorp [Member] | Unit 3 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	10%
PacifiCorp [Member] | Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	10%
PGE [Member] | Unit 3 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	20%
PGE [Member] | Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	20%
PSE [Member] | Unit 3 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	25%
PSE [Member] | Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	25%		25%
NorthWestern [Member] | Unit 4 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	30%	15%
Talen [Member] | Unit 3 [Member]
Loss Contingencies [Line Items]
Owners percentage interest	30%

Information by Business Segme_3

Information by Business Segments - Additional Information (Details)	9 Months Ended
	Sep. 30, 2023 ReportableSegments
Segment Reporting [Abstract]
Number of reportable segments	1

Information by Business Segme_4

Information by Business Segments - Schedule of Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating revenues	$ 379,626	$ 359,446	$ 1,234,194	$ 1,200,058
Resource costs	148,282	147,784	482,454	492,049
Other operating expenses	103,072	102,742	312,881	305,617
Depreciation and amortization	66,905	63,516	198,272	188,961
Income (loss) from operations	38,087	19,402	158,496	126,654
Interest expense	35,484	29,835	106,765	86,714
Income tax expense (benefit)	(3,786)	157	(16,224)	(11,678)
Net income (loss)	14,716	(5,798)	87,045	77,220
Capital expenditures	132,531	120,663	359,277	332,065
Total Assets	7,470,030		7,470,030		$ 7,417,350
Operating Segments [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	379,524	359,292	1,233,827	1,199,639
Resource costs	148,282	147,784	482,454	492,049
Other operating expenses	102,469	101,701	310,518	300,710
Depreciation and amortization	66,860	63,484	198,196	188,867
Income (loss) from operations	38,633	20,321	160,568	131,236
Interest expense	35,352	29,703	106,374	86,327
Income tax expense (benefit)	(3,809)	218	(15,301)	(13,658)
Net income (loss)	13,786	(5,759)	89,624	69,533
Capital expenditures	132,531	120,663	359,277	331,309
Total Assets	7,297,676		7,297,676		7,240,486
Operating Segments [Member] | Avista Utilities [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	369,673	349,655	1,198,419	1,167,042
Resource costs	146,793	146,384	478,947	489,029
Other operating expenses	98,609	98,062	299,274	289,828
Depreciation and amortization	64,125	60,780	190,008	180,765
Income (loss) from operations	37,081	18,660	148,897	121,476
Interest expense	33,896	28,214	102,014	81,864
Income tax expense (benefit)	(3,845)	197	(17,349)	(14,728)
Net income (loss)	13,498	(5,987)	83,935	65,241
Capital expenditures	127,666	116,809	347,264	324,123
Total Assets	7,026,484		7,026,484		6,976,164
Operating Segments [Member] | Alaska Electric Light & Power [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	9,851	9,637	35,408	32,597
Resource costs	1,489	1,400	3,507	3,020
Other operating expenses	3,860	3,639	11,244	10,882
Depreciation and amortization	2,735	2,704	8,188	8,102
Income (loss) from operations	1,552	1,661	11,671	9,760
Interest expense	1,456	1,489	4,360	4,463
Income tax expense (benefit)	36	21	2,048	1,070
Net income (loss)	288	228	5,689	4,292
Capital expenditures	4,865	3,854	12,013	7,186
Total Assets	271,192		271,192		264,322
Other [Member] | Non-Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	102	154	367	419
Resource costs	0	0	0	0
Other operating expenses	603	1,041	2,363	4,907
Depreciation and amortization	45	32	76	94
Income (loss) from operations	(546)	(919)	(2,072)	(4,582)
Interest expense	538	243	1,333	508
Income tax expense (benefit)	23	(61)	(923)	1,980
Net income (loss)	930	(39)	(2,579)	7,687
Capital expenditures	0	0	0	756
Total Assets	190,853		190,853		187,027
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
Resource costs	0	0	0	0
Other operating expenses	0	0	0	0
Depreciation and amortization	0	0	0	0
Income (loss) from operations	0	0	0	0
Interest expense	(406)	(111)	(942)	(121)
Income tax expense (benefit)	0	0	0	0
Net income (loss)	0	0	0	0
Capital expenditures	0	$ 0	0	$ 0
Total Assets	$ (18,499)		$ (18,499)		$ (10,163)