Avista (AVA) 10-Q 7 Aug 19 2019 Q2 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 02, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	AVISTA CORPORATION
Amendment Flag	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Title of 12(b) Security	Common Stock
Entity Information, Former Legal or Registered Name	None
City Area Code	509
Entity Incorporation, State or Country Code	WA
Document Transition Report	false
Document Quarterly Report	true
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Entity File Number	1-3701
Entity Tax Identification Number	91-0462470
Entity Address, Address Line One	1411 East Mission Avenue
Entity Address, City or Town	Spokane
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	99202-2600
Local Phone Number	489-0500
Trading Symbol	AVA
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000104918
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		66,111,437

Consolidated Statements Of Inco

Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating Revenues:
Utility revenues, exclusive of alternative revenue programs	$ 288,826	$ 309,134	$ 682,067	$ 717,490
Alternative revenue programs	9,725	3,570	5,067	(2,369)
Total utility revenues	298,551	312,704	687,134	715,121
Non-utility revenues	2,261	6,594	10,159	13,538
Total operating revenues	300,812	319,298	697,293	728,659
Utility operating expenses:
Resource costs	88,439	105,969	225,786	260,587
Other operating expenses	87,720	81,078	171,698	158,376
Merger transaction costs	11	983	19,675	1,655
Depreciation and amortization	55,479	45,651	104,393	90,384
Taxes other than income taxes	22,908	25,596	54,851	56,425
Other non-utility operating expenses:
Other operating expenses	6,332	6,543	13,687	13,367
Depreciation and amortization	155	199	364	380
Total operating expenses	261,044	266,019	590,454	581,174
Income from operations	39,768	53,279	106,839	147,485
Interest expense	25,511	25,170	51,162	49,946
Interest Expense, Other	351	302	708	555
Capitalized interest	(1,101)	(1,139)	(2,029)	(2,107)
Merger termination fee	0	0	(103,000)
Other income-net	(8,268)	(1,907)	(9,175)	2,572
Income before income taxes	23,275	30,853	169,173	96,519
Income tax expense (benefit)	(1,741)	5,209	28,276	15,919
Net income	25,016	25,644	140,897	80,600
Net income attributable to noncontrolling interests	303	(67)	216	(133)
Net income attributable to Avista Corporation shareholders	$ 25,319	$ 25,577	$ 141,113	$ 80,467
Weighted-average common shares outstanding (thousands), basic	65,894	65,677	65,814	65,658
Weighted-average common shares outstanding (thousands), diluted	65,963	65,983	65,883	65,957
Earnings per common share attributable to Avista Corporation shareholders:
Basic	$ 0.38	$ 0.39	$ 2.14	$ 1.23
Diluted	$ 0.38	$ 0.39	$ 2.14	$ 1.22

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 25,016	$ 25,644	$ 140,897	$ 80,600
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	161	204	321	408
Total other comprehensive loss	161	204	321	408
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	25,177	25,848	141,218	81,008
Net income attributable to noncontrolling interests	303	(67)	216	(133)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 25,480	$ 25,781	$ 141,434	$ 80,875

Consolidated Statements Of Co_2

Consolidated Statements Of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	$ 42	$ 54	$ 85	$ 109

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current Assets:
Cash and cash equivalents	$ 17,231	$ 14,656
Accounts and notes receivable-less allowances of $3,415 and $5,233, respectively	115,493	165,824
Materials and supplies, fuel stock and stored natural gas	67,659	63,881
Regulatory assets	38,785	48,552
Other current assets	30,599	54,010
Total current assets	269,767	346,923
Net utility property	4,684,654	4,648,930
Goodwill	52,426	57,672
Other regulatory assets	630,451	614,354
Other property and investments-net	240,630	114,697
Total assets	5,877,928	5,782,576
Current Liabilities:
Accounts payable	80,619	108,372
Current portion of long-term debt and capital leases	104,993	107,645
Short-term borrowings	169,000	190,000
Regulatory liabilities	37,954	113,209
Other current liabilities	124,169	120,358
Total current liabilities	516,735	639,584
Long-term debt and capital leases	1,701,434	1,755,529
Long-term debt to affiliated trusts	51,547	51,547
Pensions and other postretirement benefits	214,983	222,537
Deferred income taxes	508,139	487,602
Non-current regulatory liabilities	789,655	780,701
Other non-current liabilities and deferred credits	211,401	71,031
Total liabilities	3,993,894	4,008,531
Avista Corporation Stockholders’ Equity:
Common stock, no par value; 200,000,000 shares authorized; 65,668,477 and 65,494,333 shares issued and outstanding as of March 31, 2018 and December 31, 2017, respectively	1,157,024	1,136,491
Accumulated other comprehensive loss	(7,545)	(7,866)
Retained earnings	734,555	644,595
Total Avista Corporation shareholders’ equity	1,884,034	1,773,220
Noncontrolling Interests	0	825
Total equity	1,884,034	1,774,045
Total liabilities and equity	$ 5,877,928	$ 5,782,576

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts and notes receivable, allowances	$ 3,415	$ 5,233
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares outstanding	66,111,317	65,688,356

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating Activities:
Net income	$ 140,897	$ 80,600
Non-cash items included in net income:
Depreciation and amortization	104,757	92,584
Provision for deferred income taxes	5,577	(1,272)
Power and natural gas cost amortizations (deferrals), net	(47,716)	6,701
Amortization of debt expense	1,338	1,635
Amortization of investment in exchange power	1,225	1,225
Stock-based compensation expense	7,009	3,878
Equity-related AFUDC	(3,253)	(2,845)
Pension and other postretirement benefit expense	18,040	16,025
Other regulatory assets and liabilities and deferred debits and credits	1,122	21,323
Change in decoupling regulatory deferral	(5,444)	2,226
Gain on sale of METALfx (before payment of transaction costs)	(6,477)	0
Other	(3,904)	2,108
Contributions to defined benefit pension plan	(14,600)	(14,600)
Cash paid for settlement of interest rate swap agreements	0	(31,484)
Cash received for settlement of interest rate swap agreements	0	5,594
Changes in certain current assets and liabilities:
Accounts and notes receivable	47,771	65,843
Materials and supplies, fuel stock and natural gas stored	(7,225)	1,174
Collateral posted for derivative instruments	47,352	44,080
Other current assets	(8,783)	3,832
Accounts payable	(19,393)	(21,642)
Other current liabilities	(5,622)	(1,560)
Net cash provided by operating activities	252,671	275,425
Investing Activities:
Utility property capital expenditures (excluding equity-related AFUDC)	(199,988)	(183,132)
Issuance of notes receivable at subsidiaries	(900)	(2,780)
Equity and property investments made by subsidiaries	(6,624)	(7,431)
Proceeds from sale of METALfx (net of cash sold)	16,407	0
Other	1,072	438
Net cash used in investing activities	(190,033)	(192,905)
Financing Activities:
Net decrease in short-term borrowings	(21,000)	(105,398)
Proceeds from issuance of long-term debt	0	374,621
Maturity of long-term debt and capital leases	(1,330)	(276,170)
Issuance of common stock	14,929	1,227
Cash dividends paid	(51,153)	(49,101)
Other	(1,509)	(8,538)
Net cash used in financing activities	(60,063)	(63,359)
Net increase in cash and cash equivalents	2,575	19,161
Cash and cash equivalents at beginning of period	14,656	16,172
Cash and cash equivalents at end of period	$ 17,231	$ 35,333

Consolidated Statements Of Equi

Consolidated Statements Of Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.7450
Beginning Balance (in shares) at Dec. 31, 2017		65,494,333
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued		193,159
Ending Balance (in shares) at Jun. 30, 2018		65,687,492
Beginning Balance at Dec. 31, 2017		$ 1,133,448	$ (8,090)	$ 604,470
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Equity compensation expense		3,558
Issuance of common stock, net of issuance costs		1,227
Payment of minimum tax withholdings for share-based payment awards		(3,929)
Other comprehensive income	$ 408		408
Reclassification of excess income tax benefits			(1,742)	1,742
Net income attributable to Avista Corporation shareholders	80,467			80,467
Cash dividends paid (common stock)				(49,101)
Ending Balance at Jun. 30, 2018	$ 1,762,707	$ 1,134,304	(9,424)	637,578
Beginning Balance Noncontrolling Interest at Dec. 31, 2017					$ 656
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Net income (loss) attributable to noncontrolling interests					133
Cash dividends paid to subsidiary noncontrolling interests					(540)
Deconsolidation of noncontrolling interests related to sale of METALfx					0
Ending Balance Noncontrolling Interest at Jun. 30, 2018					249
Common Stock, Dividends, Per Share, Cash Paid	$ 0.3725
Beginning Balance (in shares) at Mar. 31, 2018		65,668,477
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued		19,015
Ending Balance (in shares) at Jun. 30, 2018		65,687,492
Beginning Balance at Mar. 31, 2018		$ 1,131,549	(9,628)	636,468
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Equity compensation expense		1,760
Issuance of common stock, net of issuance costs		995
Payment of minimum tax withholdings for share-based payment awards		0
Other comprehensive income	$ 204		204
Reclassification of excess income tax benefits			0	0
Net income attributable to Avista Corporation shareholders	25,577			25,577
Cash dividends paid (common stock)				(24,467)
Ending Balance at Jun. 30, 2018	1,762,707	$ 1,134,304	(9,424)	637,578
Beginning Balance Noncontrolling Interest at Mar. 31, 2018					182
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Net income (loss) attributable to noncontrolling interests					67
Cash dividends paid to subsidiary noncontrolling interests					0
Deconsolidation of noncontrolling interests related to sale of METALfx					0
Ending Balance Noncontrolling Interest at Jun. 30, 2018					249
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Total Avista Corporation shareholders’ equity	1,762,458
Total Avista Corporation shareholders’ equity	$ 1,773,220
Common Stock, Dividends, Per Share, Cash Paid	$ 0.7750
Beginning Balance (in shares) at Dec. 31, 2018	65,688,356	65,688,356
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued		422,961
Ending Balance (in shares) at Jun. 30, 2019	66,111,317	66,111,317
Beginning Balance at Dec. 31, 2018	$ 1,774,045	$ 1,136,491	(7,866)	644,595
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Equity compensation expense		6,495
Issuance of common stock, net of issuance costs		14,929
Payment of minimum tax withholdings for share-based payment awards		(891)
Other comprehensive income	321		321
Reclassification of excess income tax benefits			0	0
Net income attributable to Avista Corporation shareholders	141,113			141,113
Cash dividends paid (common stock)				(51,153)
Ending Balance at Jun. 30, 2019	1,884,034	$ 1,157,024	(7,545)	734,555
Beginning Balance Noncontrolling Interest at Dec. 31, 2018	825				825
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Net income (loss) attributable to noncontrolling interests					(216)
Cash dividends paid to subsidiary noncontrolling interests					0
Deconsolidation of noncontrolling interests related to sale of METALfx					(609)
Ending Balance Noncontrolling Interest at Jun. 30, 2019	$ 0				0
Common Stock, Dividends, Per Share, Cash Paid	$ 0.3875
Beginning Balance (in shares) at Mar. 31, 2019		65,749,932
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued		361,385
Ending Balance (in shares) at Jun. 30, 2019	66,111,317	66,111,317
Beginning Balance at Mar. 31, 2019		$ 1,140,242	(7,706)	734,774
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Equity compensation expense		2,043
Issuance of common stock, net of issuance costs		14,739
Payment of minimum tax withholdings for share-based payment awards		0
Other comprehensive income	$ 161		161
Reclassification of excess income tax benefits			0	0
Net income attributable to Avista Corporation shareholders	25,319			25,319
Cash dividends paid (common stock)				(25,538)
Ending Balance at Jun. 30, 2019	1,884,034	$ 1,157,024	$ (7,545)	$ 734,555
Beginning Balance Noncontrolling Interest at Mar. 31, 2019					912
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Net income (loss) attributable to noncontrolling interests					(303)
Cash dividends paid to subsidiary noncontrolling interests					0
Deconsolidation of noncontrolling interests related to sale of METALfx					(609)
Ending Balance Noncontrolling Interest at Jun. 30, 2019	0				$ 0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Total Avista Corporation shareholders’ equity	$ 1,884,034

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Business Avista Corp. is primarily an electric and natural gas utility with certain other business ventures. Avista Utilities is an operating division of Avista Corp., comprising its regulated utility operations in the Pacific Northwest. Avista Utilities provides electric distribution and transmission, and natural gas distribution services in parts of eastern Washington and northern Idaho. Avista Utilities also provides natural gas distribution service in parts of northeastern and southwestern Oregon. Avista Utilities has electric generating facilities in Washington, Idaho, Oregon and Montana. Avista Utilities also supplies electricity to a small number of customers in Montana, most of whom are employees who operate the Company's Noxon Rapids generating facility. AERC is a wholly-owned subsidiary of Avista Corp. The primary subsidiary of AERC is AEL&P, which comprises Avista Corp.'s regulated utility operations in Alaska. Avista Capital, a wholly owned non-regulated subsidiary of Avista Corp., is the parent company of all of the subsidiary companies in the non-utility businesses, with the exception of AJT Mining Properties, Inc., which is a subsidiary of AERC. See Note 16 for business segment information. See Note 18 for discussion of the sale of METALfx, an unregulated subsidiary of the Company. Basis of Reporting The condensed consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying condensed consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants. Derivative Assets and Liabilities Derivatives are recorded as either assets or liabilities on the Condensed Consolidated Balance Sheets measured at estimated fair value. The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and costs result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rate cases. The resulting regulatory assets associated with energy commodity derivative instruments have been concluded to be probable of recovery through future rates. Substantially all forward contracts to purchase or sell power and natural gas are recorded as derivative assets or liabilities at estimated fair value with an offsetting regulatory asset or liability. Contracts that are not considered derivatives are accounted for on the accrual basis until they are settled or realized unless there is a decline in the fair value of the contract that is determined to be other-than-temporary. For interest rate swap derivatives, Avista Corp. records all mark-to-market gains and losses in each accounting period as assets and liabilities, as well as offsetting regulatory assets and liabilities, such that there is no income statement impact. The interest rate swap derivatives are risk management tools similar to energy commodity derivatives. Upon settlement of interest rate swap derivatives, the 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, as well as derivatives related to interest rate swaps and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 11 for the Company’s fair value disclosures. Contingencies The Company has unresolved regulatory, legal and tax issues which have inherently uncertain outcomes. The Company accrues a loss contingency if it is probable that a liability has been incurred and the amount of the loss or impairment can be reasonably estimated. The Company also discloses loss contingencies that do not meet these conditions for accrual if there is a reasonable possibility that a material loss may be incurred. As of June 30, 2019 , the Company has not recorded any significant amounts related to unresolved contingencies. See Note 15 for further discussion of the Company's commitments and contingencies.

New Accounting Standards

New Accounting Standards	6 Months Ended
	Jun. 30, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Standards	NEW ACCOUNTING STANDARDS ASU No. 2016-02, "Leases (Topic 842)" ASU No. 2018-01, "Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842" ASU No. 2018-11, "Leases (Topic 842): Targeted Improvements" On January 1, 2019, the Company adopted ASU No. 2016-02, which outlines a model for entities to use in accounting for leases and supersedes previous lease accounting guidance, as well as several practical expedients in ASU Nos. 2018-01 and 2018-11. The Company adopted ASU No. 2016-02 utilizing a modified retrospective adoption method with the "package of three" and hindsight practical expedients offered by the standard. The "package of three" provides for an entity to not reassess at adoption whether any expired or existing contracts are deemed, for accounting purposes, to be or contain leases, the classification of any expired or existing leases, and any initial direct costs for any existing leases. As a result, the Company did not reassess existing or expired contracts under the new lease guidance and it did not reassess the classification of any existing leases. The Company used the benefit of hindsight in determining both term and impairments associated with any existing leases. Use of this practical expedient has resulted in lease terms that best represent management's expectations with respect to use of the underlying asset but did not result in recognition of any impairment. The Company elected to adopt ASU No. 2018-01, which allows an entity to exclude from application of Topic 842 all easements executed prior to January 1, 2019. In addition, the Company elected to adopt the "comparatives under 840" practical expedient offered in ASU No. 2018-11, which allows an entity to apply the new lease standard at the adoption date, recognizing any necessary cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption and presenting comparative periods in the financial statements under ASC 840 (previous lease accounting guidance). Adoption of the standard did not result in a cumulative effect adjustment within the Company's financial statements. As allowed by ASU No. 2016-02, the Company elected not to apply the requirements of the standard to short-term leases, those leases with an initial term of 12 months or less. These leases are not recorded on the balance sheet and are immaterial to the financial statements. Adoption of the standard impacted the Company's Condensed Consolidated Balance Sheet through recognition of right-of-use (ROU) assets and lease liabilities for the Company's operating leases. Accounting for finance leases (formerly capital leases) remained substantially unchanged. See Note 5 for further information on the Company's leases. ASU No. 2018-02 “Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” In February 2018, the FASB issued ASU No. 2018-02, which amended the guidance for reporting comprehensive income. This ASU allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the enactment of the TCJA in December 2017. This ASU became effective for periods beginning after December 15, 2018 and early adoption was permitted. Upon adoption, the requirements of this ASU must be applied either in the period of adoption or retrospectively to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the TCJA is recognized. The Company early adopted this standard effective January 1, 2018 and elected to apply the guidance during the period of adoption rather than apply the standard retrospectively. As a result, the Company reclassified $1.7 million in tax benefits from accumulated other comprehensive loss to retained earnings during the six months ended June 30, 2018 . ASU 2018-13 "Fair Value Measurement (Topic 820)" In August 2018, the FASB issued ASU No. 2018-13, which amends the fair value measurement disclosure requirements of ASC 820. The requirements of this ASU include additional disclosure regarding the range and weighted average used to develop significant unobservable inputs for Level 3 fair value estimates and the elimination of certain other previously required disclosures, such as the narrative description of the valuation process for Level 3 fair value measurements. This ASU is effective for periods beginning after December 15, 2019 and early adoption is permitted. Entities have the option to early adopt the eliminated or modified disclosure requirements and delay the adoption of all the new disclosure requirements until the effective date of the ASU. The Company is in the process of evaluating this standard; however, it has determined that it will not early adopt any portion of this standard as of June 30, 2019 . ASU No. 2018-14 "Compensation - Retirement Benefits - Defined Benefit Plans - General (Subtopic 715-20)" In August 2018, the FASB issued ASU No. 2018-14, which amends ASC 715 to add, remove and/or clarify certain disclosure requirements related to defined benefit pension and other postretirement plans. The additional disclosure requirements are primarily narrative discussion of significant changes in the benefit obligations and plan assets. The removed disclosures are primarily information about accumulated other comprehensive income expected to be recognized over the next year and the effects of changes associated with assumed health care costs. This ASU is effective for periods beginning after December 15, 2021 and early adoption is permitted. The Company is in the process of evaluating this standard; however, it has determined that it will not early adopt this standard as of June 30, 2019 .

Balance Sheet Components Balanc

Balance Sheet Components Balance Sheet Components (Notes)	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Supplemental Balance Sheet Disclosures [Text Block]	BALANCE SHEET COMPONENTS Materials and Supplies, Fuel Stock and Stored Natural Gas Inventories of materials and supplies, fuel stock and stored natural gas are recorded at average cost for our regulated operations and the lower of cost or market for our non-regulated operations and consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Materials and supplies $ 46,886 $ 47,403 Fuel stock 6,332 4,869 Stored natural gas 14,441 11,609 Total $ 67,659 $ 63,881 Other Current Assets Other current assets consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Collateral posted for derivative instruments after netting with outstanding derivative liabilities $ — $ 26,809 Prepayments 24,515 17,536 Other 6,084 9,665 Total $ 30,599 $ 54,010 Net Utility Property Net utility property consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Utility plant in service $ 6,262,789 $ 6,209,968 Construction work in progress 191,845 160,598 Total 6,454,634 6,370,566 Less: Accumulated depreciation and amortization 1,769,980 1,721,636 Total net utility property $ 4,684,654 $ 4,648,930 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 June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Operating lease ROU assets $ 70,442 $ — Finance lease ROU assets 52,800 — Non-utility property 28,438 31,355 Equity investments 36,921 29,257 Investment in affiliated trust 11,547 11,547 Notes receivable 11,376 11,073 Deferred compensation assets 8,557 8,400 Other 20,549 23,065 Total $ 240,630 $ 114,697 Other Current Liabilities Other current liabilities consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Accrued taxes other than income taxes $ 35,502 $ 36,858 Employee paid time off accruals 22,092 20,992 Accrued interest 16,536 16,704 Current portion of pensions and other postretirement benefits 11,175 9,151 Derivative liabilities 9,274 3,908 Other current liabilities 29,590 32,745 Total other current liabilities $ 124,169 $ 120,358 Other Non-Current Liabilities and Deferred Credits Other non-current liabilities and deferred credits consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Operating lease liabilities $ 68,228 $ — Finance lease liabilities 53,150 — Deferred investment tax credits 31,172 29,725 Asset retirement obligations 18,595 18,266 Derivative liabilities 27,198 10,300 Other 13,058 12,740 Total $ 211,401 $ 71,031 Regulatory Assets and Liabilities Regulatory assets and liabilities consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, 2019 December 31, 2018 Current Non-Current Current Non-Current Regulatory Assets Energy commodity derivatives $ 25,125 $ 10,764 $ 41,428 $ 16,866 Decoupling surcharge 6,498 16,167 3,408 17,501 Pension and other postretirement benefit plans — 221,454 — 228,062 Interest rate swaps — 155,787 — 133,854 Deferred income taxes — 95,217 — 91,188 Settlement with Coeur d'Alene Tribe — 41,988 — 42,643 Demand side management programs — 13,705 — 19,674 Utility plant to be abandoned — 25,273 — 24,334 Other regulatory assets 7,162 50,096 3,716 40,232 Total regulatory assets $ 38,785 $ 630,451 $ 48,552 $ 614,354 Regulatory Liabilities Income tax related liabilities $ 23,079 $ 418,039 $ 27,997 $ 425,613 Deferred natural gas costs 1,852 — 40,713 — Deferral power costs 6,612 32,617 25,072 16,933 Decoupling rebate 437 2,861 6,782 204 Utility plant retirement costs — 302,734 — 297,379 Interest rate swaps — 17,659 — 28,078 Other regulatory liabilities 5,974 15,745 12,645 12,494 Total regulatory liabilities $ 37,954 $ 789,655 $ 113,209 $ 780,701

Revenue Revenue (Notes)

Revenue Revenue (Notes)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	REVENUE ASC 606 defines the core principle of the revenue recognition model is that an entity should identify the various performance obligations in a contract, allocate the transaction price among the performance obligations and recognize revenue when (or as) the entity satisfies each performance obligation. Utility Revenues Revenue from Contracts with Customers General The majority of Avista Corp.’s revenue is from rate-regulated sales of electricity and natural gas to retail customers, which has two performance obligations, (1) having service available for a specified period (typically a month at a time) and (2) the delivery of energy to customers. The total energy price generally has a fixed component (basic charge) related to having service available and a usage-based component, related to the delivery and consumption of energy. The commodity is sold and/or delivered to and consumed by the customer simultaneously, and the provisions of the relevant utility commission authorization determine the charges the Company may bill the customer. Given that all revenue recognition criteria are met upon the delivery of energy to customers, revenue is recognized immediately at that time. Revenues from contracts with customers are presented in the Condensed Consolidated Statements of Income in the line item "Utility revenues, exclusive of alternative revenue programs." Non-Derivative Wholesale Contracts The Company has certain wholesale contracts which are not accounted for as derivatives and, accordingly, are within the scope of ASC 606 and considered revenue from contracts with customers. Revenue is recognized as energy is delivered to the customer or the service is available for a specified period of time, consistent with the discussion of rate-regulated sales above. Alternative Revenue Programs (Decoupling) ASC 606 retained existing GAAP associated with alternative revenue programs, which specified that alternative revenue programs are contracts between an entity and a regulator of utilities, not a contract between an entity and a customer. GAAP requires that an entity present revenue arising from alternative revenue programs separately from revenues arising from contracts with customers on the face of the Condensed Consolidated Statements of Income. The Company's decoupling mechanisms (also known as a FCA in Idaho) qualify as alternative revenue programs. Decoupling revenue deferrals are recognized in the Condensed Consolidated Statements of Income during the period they occur (i.e. during the period of revenue shortfall or excess due to fluctuations in customer usage), subject to certain limitations, and a regulatory asset or liability is established that will be surcharged or rebated to customers in future periods. GAAP requires that for any alternative revenue program, like decoupling, the revenue must be expected to be collected from customers within 24 months of the deferral to qualify for recognition in the current period Condensed Consolidated Statement of Income. Any amounts included in the Company's decoupling program that are not expected to be collected from customers within 24 months are not recorded in the financial statements until the period in which revenue recognition criteria are met. The amounts expected to be collected from customers within 24 months represents an estimate that must be made by the Company on an ongoing basis due to it being based on the volumes of electric and natural gas sold to customers on a go-forward basis. Derivative Revenue Most wholesale electric and natural gas transactions (including both physical and financial transactions), and the sale of fuel are considered derivatives, which are specifically scoped out of ASC 606. As such, these revenues are disclosed separately from revenue from contracts with customers. Revenue is recognized for these items upon the settlement/expiration of the derivative contract. Derivative revenue includes those transactions that are entered into and settled within the same month. Other Utility Revenue Other utility revenue includes rent, revenues from the lineman training school, sales of materials, late fees and other charges that do not represent contracts with customers. Other utility revenue also includes the provision for earnings sharing and the deferral and amortization of refunds to customers associated with the TCJA. This revenue is scoped out of ASC 606, as this revenue does not represent items where a customer is a party that has contracted with the Company to obtain goods or services that are an output of the Company’s ordinary activities in exchange for consideration. As such, these revenues are presented separately from revenue from contracts with customers. Other Considerations for Utility Revenues Gross Versus Net Presentation Revenues and resource costs from Avista Utilities’ settled energy contracts that are “booked out” (not physically delivered) are reported on a net basis as part of derivative revenues. Utility-related taxes collected from customers (primarily state excise taxes and city utility taxes) are taxes that are imposed on Avista Utilities as opposed to being imposed on its customers; therefore, Avista Utilities is the taxpayer and records these transactions on a gross basis in revenue from contracts with customers and operating expense (taxes other than income taxes). The utility-related taxes collected from customers at AEL&P are imposed on the customers rather than AEL&P; therefore, the customers are the taxpayers and AEL&P is acting as their agent. As such, these transactions at AEL&P are presented on a net basis within revenue from contracts with customers. Utility-related taxes that were included in revenue from contracts with customers were as follows for the three and six months ended June 30 (dollars in thousands): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Utility-related taxes $ 12,688 $ 12,986 $ 31,777 $ 32,153 Non-Utility Revenues Revenue from Contracts with Customers Non-utility revenues from contracts with customers are primarily derived from the operations of METALfx (through the date of its sale in April 2019, see Note 18 for further discussion). The contracts associated with METALfx have one performance obligation, the delivery of a product, and revenues are recognized when the risk of loss transfers to the customer, which occurs when products are shipped. Significant Judgments and Unsatisfied Performance Obligations The only significant judgments involving revenue recognition are estimates surrounding unbilled revenue and receivables from contracts with customers and estimates surrounding the amount of decoupling revenues that will be collected from customers within 24 months (discussed above). The Company has certain capacity arrangements, where the Company has a contractual obligation to provide either electric or natural gas capacity to its customers for a fixed fee. Most of these arrangements are paid for in arrears by the customers and do not result in deferred revenue and only result in receivables from the customers. The Company does have one capacity agreement where the customer makes payments throughout the year and depending on the timing of the customer payments, it can result in an immaterial amount of deferred revenue or a receivable from the customer. As of June 30, 2019 , the Company estimates it had unsatisfied capacity performance obligations of $7.9 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 six months ended June 30 (dollars in thousands): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Avista Utilities Revenue from contracts with customers $ 231,605 $ 239,113 $ 585,907 $ 593,275 Derivative revenues 42,128 56,357 66,255 114,749 Alternative revenue programs 9,725 3,570 5,067 (2,369 ) Deferrals and amortizations for rate refunds to customers 2,512 982 4,647 (18,840 ) Other utility revenues 3,838 2,200 5,634 4,161 Total Avista Utilities 289,808 302,222 667,510 690,976 AEL&P Revenue from contracts with customers 8,620 10,759 19,356 25,409 Deferrals and amortizations for rate refunds to customers (47 ) (427 ) (95 ) (1,549 ) Other utility revenues 170 150 363 285 Total AEL&P 8,743 10,482 19,624 24,145 Other Revenue from contracts with customers 2,024 6,324 9,671 13,053 Other revenues 237 270 488 485 Total other 2,261 6,594 10,159 13,538 Total operating revenues $ 300,812 $ 319,298 $ 697,293 $ 728,659 Utility Revenue from Contracts with Customers by Type and Service The following table disaggregates revenue from contracts with customers associated with the Company's utility operations for the three and six months ended June 30 (dollars in thousands): 2019 2018 Avista Utilities AEL&P Total Utility Avista Utilities AEL&P Total Utility Three months ended June 30: ELECTRIC OPERATIONS Revenue from contracts with customers Residential $ 72,886 $ 3,724 $ 76,610 $ 74,818 $ 4,155 $ 78,973 Commercial and governmental 76,375 4,837 81,212 76,462 6,541 83,003 Industrial 26,245 — 26,245 27,985 — 27,985 Public street and highway lighting 1,897 59 1,956 1,899 63 1,962 Total retail revenue 177,403 8,620 186,023 181,164 10,759 191,923 Transmission 4,250 — 4,250 4,171 — 4,171 Other revenue from contracts with customers 4,379 — 4,379 3,919 — 3,919 Total revenue from contracts with customers $ 186,032 $ 8,620 $ 194,652 $ 189,254 $ 10,759 $ 200,013 NATURAL GAS OPERATIONS Revenue from contracts with customers Residential $ 27,937 $ — $ 27,937 $ 30,767 $ — $ 30,767 Commercial 13,369 — 13,369 14,668 — 14,668 Industrial and interruptible 1,103 — 1,103 1,078 — 1,078 Total retail revenue 42,409 — 42,409 46,513 — 46,513 Transportation 2,039 — 2,039 2,221 — 2,221 Other revenue from contracts with customers 1,125 — 1,125 1,125 — 1,125 Total revenue from contracts with customers $ 45,573 $ — $ 45,573 $ 49,859 $ — $ 49,859 Six months ended June 30: ELECTRIC OPERATIONS Residential $ 188,279 $ 9,576 $ 197,855 $ 189,571 $ 10,693 $ 200,264 Commercial and governmental 155,621 9,658 165,279 155,371 14,585 169,956 Industrial 51,493 — 51,493 53,104 — 53,104 Public street and highway lighting 3,800 122 3,922 3,758 131 3,889 Total retail revenue 399,193 19,356 418,549 401,804 25,409 427,213 Transmission 9,402 — 9,402 8,001 — 8,001 Other revenue from contracts with customers 12,573 — 12,573 10,210 — 10,210 Total electric revenue from contracts with customers $ 421,168 $ 19,356 $ 440,524 $ 420,015 $ 25,409 $ 445,424 2019 2018 Avista Utilities AEL&P Total Utility Avista Utilities AEL&P Total Utility NATURAL GAS OPERATIONS Residential $ 105,272 $ — $ 105,272 $ 111,421 $ — $ 111,421 Commercial 49,964 — 49,964 52,040 — 52,040 Industrial and interruptible 2,730 — 2,730 2,761 — 2,761 Total retail revenue 157,966 — 157,966 166,222 — 166,222 Transportation 4,523 — 4,523 4,788 — 4,788 Other revenue from contracts with customers 2,250 — 2,250 2,250 — 2,250 Total natural gas revenue from contracts with customers $ 164,739 $ — $ 164,739 $ 173,260 $ — $ 173,260

Leases Leases (Notes)

Leases Leases (Notes)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Lessee, Operating Leases [Text Block]	LEASES ASC 842, which outlines a model for entities to use in accounting for leases and supersedes previous lease accounting guidance, became effective on January 1, 2019. The core principle of the model is that an entity should recognize the ROU assets and liabilities that arise from leases on the balance sheet and depreciate or amortize the asset and liability over the term of the lease, as well as provide disclosure to enable users of the condensed consolidated financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. Significant Judgments and Assumptions The Company determines if an arrangement is a lease, as well as its classification, at its inception. ROU assets represent the Company's right to use an underlying asset for the lease term, and lease liabilities represent the Company's obligation to make lease payments arising from the lease. Operating and finance lease ROU assets and lease liabilities are recognized at the commencement date of the agreement based on the present value of lease payments over the lease term. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date to determine the present value of lease payments. The implicit rate is used when it is readily determinable. The operating and finance lease ROU assets also include any lease payments made and exclude lease incentives, if any, that accrue to the benefit of the lessee. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Any difference between lease expense and cash paid for leased assets is recognized as a regulatory asset or regulatory liability. Description of Leases The Company has operating leases for land associated with its utility operations, as well as communication sites which support network and radio communications within its service territory. The Company's leases have remaining terms of 1 to 74 years . Most of the Company's leases include options to extend the lease term for periods of 5 to 50 years . Options are exercised at the Company's discretion. The Company has an operating lease with the state of Montana associated with submerged land around the Company's hydroelectric facilities in the Clark Fork River basin, which expires in 2046. The terms of this lease are subject to renegotiation, depending on the outcome of ongoing litigation between Montana and NorthWestern Energy. In addition, the state of Montana and Avista Corp. are engaged in litigation regarding the lease terms. As such, amounts recorded for this lease are uncertain and amounts may change in the future depending on the outcome of the ongoing litigation. Through its wholly-owned subsidiary, AEL&P, the Company has a PPA which is treated as a finance lease for accounting purposes related to the Snettisham Hydroelectric Project, which expires in 2034. For ratemaking purposes, this lease is treated as an operating lease with a constant level of annual rental expense (straight line rent expense). Because of this regulatory treatment, any difference between the operating lease expense for ratemaking purposes and the expenses recognized under finance lease treatment (interest and amortization of the finance lease ROU asset) is recorded as a regulatory asset and amortized during the later years of the lease when the finance lease expense is less than the operating lease expense included in base rates. In 2018 and prior years, the total cost associated with the Snettisham PPA was included in resource costs. Due to the adoption of the new lease standard, the amortization of the ROU asset is now included in depreciation and amortization and the interest associated with the lease liability is now included in interest expense on the Condensed Consolidated Statement of Income. Certain of the Company's lease agreements include rental payments which are periodically adjusted over the term of the agreement based on the consumer price index. The Company's lease agreements do not include any material residual value guarantees or material restrictive covenants. Avista Corp. does not record leases with a term of 12 months or less in the Condensed Consolidated Balance Sheet. Total short-term lease costs for the three and six months ended June 30, 2019 are immaterial. Leases that Have Not Yet Commenced In June 2018, the Company finalized a lease agreement for office space in Spokane, Washington. The lease period is expected to commence in April 2020, once construction of the building is complete. The lease is an operating lease for a term of 12 years and will result in annual rent expense of approximately $1.1 million , which will be reflected in other operating expenses. In addition to base rent expense, the Company is expected to share in a portion of the annual operating expenses of the building. In March 2019, the Company signed a PPA with Clearway Energy Group (Clearway) to purchase all of the power generated from the Rattlesnake Flat Wind project in Adams County, Washington. The facility has a nameplate capacity of 144 MW and is expected to generate approximately 50 aMW. During negotiations with Clearway, Avista Corp. was involved in the selection of the preferred generation facility type. The PPA is a 20-year agreement with deliveries expected to begin in 2020. The PPA provides Avista Corp. with additional renewable energy, capacity and environmental attributes. Avista Corp. expects to recover the cost of the power purchased through its retail rates. This PPA is considered a lease under ASC 842; however, all of the payments are variable payments based on whether power is generated from the facility. Since all the payments are variable, the Company will not record a lease liability for the agreement, but the expense will be included in resource costs when it becomes operational in 2020. The components of lease expense were as follows for the three and six months ended June 30 , 2019 (dollars in thousands): Three months ended June 30, 2019 Six months ended June 30, 2019 Operating lease cost: Fixed lease cost (Other operating expenses) $ 1,106 $ 2,209 Variable lease cost (Other operating expenses) 244 487 Total operating lease cost $ 1,350 $ 2,696 Finance lease cost: Amortization of ROU asset (Depreciation and amortization) $ 910 $ 1,820 Interest on lease liabilities (Interest expense) 699 1,398 Total finance lease cost $ 1,609 $ 3,218 Supplemental cash flow information related to leases was as follows for the six months ended June 30 (dollars in thousands): 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflows: Operating lease payments $ 4,197 Interest on finance lease 1,398 Total operating cash outflows $ 5,595 Finance cash outflows: Principal payments on finance lease $ 1,330 Supplemental balance sheet information related to leases was as follows for June 30, 2019 (dollars in thousands): June 30, 2019 Operating Leases Operating lease ROU assets (Other property and investments-net and other non-current assets) $ 70,442 Other current liabilities $ 4,123 Other non-current liabilities and deferred credits 68,228 Total operating lease liabilities $ 72,351 Finance Leases Finance lease ROU assets (Other property and investments-net and other non-current assets) (a) $ 52,800 Other current liabilities (b) $ 2,730 Other non-current liabilities and deferred credits (b) 53,150 Total finance lease liabilities $ 55,880 Weighted Average Remaining Lease Term Operating leases 27.01 years Finance leases 8.39 years Weighted Average Discount Rate Operating leases 3.82 % Finance leases 4.88 % (a) At December 31, 2018, the finance lease ROU assets were included in "Net utility property" on the Condensed Consolidated Balance Sheet. Due to the adoption of ASC 842 on January 1, 2019, the Company has reclassified these amounts to "Other property and investments-net and other non-current assets" on the Condensed Consolidated Balance Sheet such that their presentation as of June 30, 2019 is consistent with operating leases. (b) At December 31, 2018, the finance lease liabilities were included in "Current portion of long-term debt" and "Long-term debt and capital leases" on the Condensed Consolidated Balance Sheet. Due to the adoption of ASC 842 on January 1, 2019, the Company has reclassified these amounts to "Other current liabilities" and "Other non-current liabilities and deferred credits" on the Condensed Consolidated Balance Sheet such that their presentation as of June 30, 2019 is consistent with operating leases. Maturities of lease liabilities (including principal and interest) were as follows as of June 30, 2019 (dollars in thousands): Operating Leases Finance Leases Remainder 2019 $ 4,170 $ 2,726 2020 4,364 5,462 2021 4,367 5,457 2022 4,375 5,460 2023 4,391 5,456 Thereafter 95,939 54,574 Total lease payments $ 117,606 $ 79,135 Less: imputed interest (45,255 ) (23,255 ) Total $ 72,351 $ 55,880 Future minimum lease payments (including principal and interest) under Topic 840 as of December 31, 2018 (dollars in thousands): Operating Leases Finance Leases 2019 $ 4,995 $ 5,455 2020 4,876 5,462 2021 4,859 5,457 2022 4,782 5,460 2023 4,780 5,456 Thereafter 102,389 54,574 Total lease payments $ 126,681 $ 81,864 Less: imputed interest — (24,654 ) Total $ 126,681 $ 57,210
Lessee, Finance Leases [Text Block]	LEASES ASC 842, which outlines a model for entities to use in accounting for leases and supersedes previous lease accounting guidance, became effective on January 1, 2019. The core principle of the model is that an entity should recognize the ROU assets and liabilities that arise from leases on the balance sheet and depreciate or amortize the asset and liability over the term of the lease, as well as provide disclosure to enable users of the condensed consolidated financial statements to assess the amount, timing, and uncertainty of cash flows arising from leases. Significant Judgments and Assumptions The Company determines if an arrangement is a lease, as well as its classification, at its inception. ROU assets represent the Company's right to use an underlying asset for the lease term, and lease liabilities represent the Company's obligation to make lease payments arising from the lease. Operating and finance lease ROU assets and lease liabilities are recognized at the commencement date of the agreement based on the present value of lease payments over the lease term. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date to determine the present value of lease payments. The implicit rate is used when it is readily determinable. The operating and finance lease ROU assets also include any lease payments made and exclude lease incentives, if any, that accrue to the benefit of the lessee. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Any difference between lease expense and cash paid for leased assets is recognized as a regulatory asset or regulatory liability. Description of Leases The Company has operating leases for land associated with its utility operations, as well as communication sites which support network and radio communications within its service territory. The Company's leases have remaining terms of 1 to 74 years . Most of the Company's leases include options to extend the lease term for periods of 5 to 50 years . Options are exercised at the Company's discretion. The Company has an operating lease with the state of Montana associated with submerged land around the Company's hydroelectric facilities in the Clark Fork River basin, which expires in 2046. The terms of this lease are subject to renegotiation, depending on the outcome of ongoing litigation between Montana and NorthWestern Energy. In addition, the state of Montana and Avista Corp. are engaged in litigation regarding the lease terms. As such, amounts recorded for this lease are uncertain and amounts may change in the future depending on the outcome of the ongoing litigation. Through its wholly-owned subsidiary, AEL&P, the Company has a PPA which is treated as a finance lease for accounting purposes related to the Snettisham Hydroelectric Project, which expires in 2034. For ratemaking purposes, this lease is treated as an operating lease with a constant level of annual rental expense (straight line rent expense). Because of this regulatory treatment, any difference between the operating lease expense for ratemaking purposes and the expenses recognized under finance lease treatment (interest and amortization of the finance lease ROU asset) is recorded as a regulatory asset and amortized during the later years of the lease when the finance lease expense is less than the operating lease expense included in base rates. In 2018 and prior years, the total cost associated with the Snettisham PPA was included in resource costs. Due to the adoption of the new lease standard, the amortization of the ROU asset is now included in depreciation and amortization and the interest associated with the lease liability is now included in interest expense on the Condensed Consolidated Statement of Income. Certain of the Company's lease agreements include rental payments which are periodically adjusted over the term of the agreement based on the consumer price index. The Company's lease agreements do not include any material residual value guarantees or material restrictive covenants. Avista Corp. does not record leases with a term of 12 months or less in the Condensed Consolidated Balance Sheet. Total short-term lease costs for the three and six months ended June 30, 2019 are immaterial. Leases that Have Not Yet Commenced In June 2018, the Company finalized a lease agreement for office space in Spokane, Washington. The lease period is expected to commence in April 2020, once construction of the building is complete. The lease is an operating lease for a term of 12 years and will result in annual rent expense of approximately $1.1 million , which will be reflected in other operating expenses. In addition to base rent expense, the Company is expected to share in a portion of the annual operating expenses of the building. In March 2019, the Company signed a PPA with Clearway Energy Group (Clearway) to purchase all of the power generated from the Rattlesnake Flat Wind project in Adams County, Washington. The facility has a nameplate capacity of 144 MW and is expected to generate approximately 50 aMW. During negotiations with Clearway, Avista Corp. was involved in the selection of the preferred generation facility type. The PPA is a 20-year agreement with deliveries expected to begin in 2020. The PPA provides Avista Corp. with additional renewable energy, capacity and environmental attributes. Avista Corp. expects to recover the cost of the power purchased through its retail rates. This PPA is considered a lease under ASC 842; however, all of the payments are variable payments based on whether power is generated from the facility. Since all the payments are variable, the Company will not record a lease liability for the agreement, but the expense will be included in resource costs when it becomes operational in 2020. The components of lease expense were as follows for the three and six months ended June 30 , 2019 (dollars in thousands): Three months ended June 30, 2019 Six months ended June 30, 2019 Operating lease cost: Fixed lease cost (Other operating expenses) $ 1,106 $ 2,209 Variable lease cost (Other operating expenses) 244 487 Total operating lease cost $ 1,350 $ 2,696 Finance lease cost: Amortization of ROU asset (Depreciation and amortization) $ 910 $ 1,820 Interest on lease liabilities (Interest expense) 699 1,398 Total finance lease cost $ 1,609 $ 3,218 Supplemental cash flow information related to leases was as follows for the six months ended June 30 (dollars in thousands): 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflows: Operating lease payments $ 4,197 Interest on finance lease 1,398 Total operating cash outflows $ 5,595 Finance cash outflows: Principal payments on finance lease $ 1,330 Supplemental balance sheet information related to leases was as follows for June 30, 2019 (dollars in thousands): June 30, 2019 Operating Leases Operating lease ROU assets (Other property and investments-net and other non-current assets) $ 70,442 Other current liabilities $ 4,123 Other non-current liabilities and deferred credits 68,228 Total operating lease liabilities $ 72,351 Finance Leases Finance lease ROU assets (Other property and investments-net and other non-current assets) (a) $ 52,800 Other current liabilities (b) $ 2,730 Other non-current liabilities and deferred credits (b) 53,150 Total finance lease liabilities $ 55,880 Weighted Average Remaining Lease Term Operating leases 27.01 years Finance leases 8.39 years Weighted Average Discount Rate Operating leases 3.82 % Finance leases 4.88 % (a) At December 31, 2018, the finance lease ROU assets were included in "Net utility property" on the Condensed Consolidated Balance Sheet. Due to the adoption of ASC 842 on January 1, 2019, the Company has reclassified these amounts to "Other property and investments-net and other non-current assets" on the Condensed Consolidated Balance Sheet such that their presentation as of June 30, 2019 is consistent with operating leases. (b) At December 31, 2018, the finance lease liabilities were included in "Current portion of long-term debt" and "Long-term debt and capital leases" on the Condensed Consolidated Balance Sheet. Due to the adoption of ASC 842 on January 1, 2019, the Company has reclassified these amounts to "Other current liabilities" and "Other non-current liabilities and deferred credits" on the Condensed Consolidated Balance Sheet such that their presentation as of June 30, 2019 is consistent with operating leases. Maturities of lease liabilities (including principal and interest) were as follows as of June 30, 2019 (dollars in thousands): Operating Leases Finance Leases Remainder 2019 $ 4,170 $ 2,726 2020 4,364 5,462 2021 4,367 5,457 2022 4,375 5,460 2023 4,391 5,456 Thereafter 95,939 54,574 Total lease payments $ 117,606 $ 79,135 Less: imputed interest (45,255 ) (23,255 ) Total $ 72,351 $ 55,880 Future minimum lease payments (including principal and interest) under Topic 840 as of December 31, 2018 (dollars in thousands): Operating Leases Finance Leases 2019 $ 4,995 $ 5,455 2020 4,876 5,462 2021 4,859 5,457 2022 4,782 5,460 2023 4,780 5,456 Thereafter 102,389 54,574 Total lease payments $ 126,681 $ 81,864 Less: imputed interest — (24,654 ) Total $ 126,681 $ 57,210

Derivatives And Risk Management

Derivatives And Risk Management	6 Months Ended
	Jun. 30, 2019
Derivative Instruments and Hedges, Assets [Abstract]
Derivatives And Risk Management	DERIVATIVES AND RISK MANAGEMENT Energy Commodity Derivatives Avista Corp. is exposed to market risks relating to changes in electricity and natural gas commodity prices and certain other fuel prices. Market risk is, in general, the risk of fluctuation in the market price of the commodity being traded and is influenced primarily by supply and demand. Market risk includes the fluctuation in the market price of associated derivative commodity instruments. Avista Corp. utilizes derivative instruments, such as forwards, futures, swap derivatives and options, in order to manage the various risks relating to these commodity price exposures. Avista Corp. has an energy resources risk policy and control procedures to manage these risks. As part of Avista Corp.'s resource procurement and management operations in the electric business, Avista Corp. engages in an ongoing process of resource optimization, which involves the economic selection from available energy resources to serve Avista Corp.'s load obligations and the use of these resources to capture available economic value through wholesale market transactions. These include sales and purchases of electric capacity and energy, fuel for electric generation, and derivative contracts related to capacity, energy and fuel. Such transactions are part of the process of matching resources with load obligations and hedging a portion of the related financial risks. These transactions range from terms of intra-hour up to multiple years. As part of its resource procurement and management of its natural gas business, Avista Corp. makes continuing projections of its natural gas loads and assesses available natural gas resources including natural gas storage availability. Natural gas resource planning typically includes peak requirements, low and average monthly requirements and delivery constraints from natural gas supply locations to Avista Corp.’s distribution system. However, daily variations in natural gas demand can be significantly different than monthly demand projections. On the basis of these projections, Avista Corp. plans and executes a series of transactions to hedge a portion of its projected natural gas requirements through forward market transactions and derivative instruments. These transactions may extend as much as four natural gas operating years (November through October) into the future. Avista Corp. also leaves a significant portion of its natural gas supply requirements unhedged for purchase in short-term and spot markets. Avista Corp. plans for sufficient natural gas delivery capacity to serve its retail customers for a theoretical peak day event. Avista Corp. generally has more pipeline and storage capacity than what is needed during periods other than a peak-day. Avista Corp. optimizes its natural gas resources by using market opportunities to generate economic value that helps mitigate fixed costs. Avista Corp. also optimizes its natural gas storage capacity by purchasing and storing natural gas when prices are traditionally lower, typically in the summer, and withdrawing during higher priced months, typically during the winter. However, if market conditions and prices indicate that Avista Corp. should buy or sell natural gas at other times during the year, Avista Corp. engages in optimization transactions to capture value in the marketplace. Natural gas optimization activities include, but are not limited to, wholesale market sales of surplus natural gas supplies, purchases and sales of natural gas to optimize use of pipeline and storage capacity, and participation in the transportation capacity release market. The following table presents the underlying energy commodity derivative volumes as of June 30, 2019 that are expected to be delivered in each respective year (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical (1) MWh Financial (1) MWh Physical (1) mmBTUs Financial (1) mmBTUs Physical (1) Financial (1) Physical (1) Financial (1) Remainder 2019 1 559 5,378 61,385 82 1,330 481 26,150 2020 — — 1,138 60,253 123 1,055 1,430 23,683 2021 — — — 17,640 — 246 1,049 8,575 2022 — — — 1,350 — — — — 2023 — — — — — — — — Thereafter — — — — — — — — The following table presents the underlying energy commodity derivative volumes as of December 31, 2018 that are expected to be delivered in each respective year (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) 2019 206 941 10,732 101,293 197 2,790 2,909 54,418 2020 — — 1,138 47,225 123 959 1,430 14,625 2021 — — — 9,670 — — 1,049 4,100 2022 — — — — — — — — 2023 — — — — — — — — Thereafter — — — — — — — — (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 delivered and will be included in the various deferral and recovery mechanisms (ERM, PCA and PGAs), or in the general rate case process, and are expected to be collected through retail rates from customers. Foreign Currency Exchange Derivatives A significant portion of Avista Corp.’s natural gas supply (including fuel for power generation) is obtained from Canadian sources. Most of those transactions are executed in U.S. dollars, which avoids foreign currency risk. A portion of Avista Corp.’s short-term natural gas transactions and long-term Canadian transportation contracts are committed based on Canadian currency prices and settled within 60 days with U.S. dollars. Avista Corp. hedges a portion of the foreign currency risk by purchasing Canadian currency exchange derivatives when such commodity transactions are initiated. The foreign currency exchange derivatives and the unhedged foreign currency risk have not had a material effect on Avista Corp.’s financial condition, results of operations or cash flows and these differences in cost related to currency fluctuations are included with natural gas supply costs for ratemaking. The following table summarizes the foreign currency exchange derivatives that Avista Corp. has outstanding as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Number of contracts 27 31 Notional amount (in United States dollars) $ 2,780 $ 4,018 Notional amount (in Canadian dollars) 3,680 5,386 Interest Rate Swap Derivatives Avista Corp. is affected by fluctuating interest rates related to a portion of its existing debt, and future borrowing requirements. Avista Corp. hedges a portion of its interest rate risk with financial derivative instruments, which may include interest rate swap derivatives and U.S. Treasury lock agreements. These interest rate swap derivatives and U.S. Treasury lock agreements are considered economic hedges against fluctuations in future cash flows associated with anticipated debt issuances. The following table summarizes the unsettled interest rate swap derivatives that Avista Corp. has outstanding as of June 30, 2019 and December 31, 2018 (dollars in thousands): Balance Sheet Date Number of Contracts Notional Amount Mandatory Cash Settlement Date June 30, 2019 6 $ 70,000 2019 6 60,000 2020 3 35,000 2021 9 100,000 2022 December 31, 2018 6 $ 70,000 2019 6 60,000 2020 2 25,000 2021 7 80,000 2022 Upon settlement of interest rate swap derivatives, the cash payments made or received are recorded as a regulatory asset or liability and are subsequently amortized as a component of interest expense over the life of the associated debt. The settled interest rate swap derivatives are also included as a part of Avista Corp.'s cost of debt calculation for ratemaking purposes. The 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 June 30, 2019 and December 31, 2018 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 June 30, 2019 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Asset Gross Liability Collateral Netted Net Asset (Liability) on Balance Sheet Foreign currency exchange derivatives Other current assets $ 33 $ — $ — $ 33 Interest rate swap derivatives Other current assets 771 (338 ) — 433 Other current liabilities — (4,771 ) — (4,771 ) Other non-current liabilities and deferred credits 631 (27,309 ) 5,030 (21,648 ) Energy commodity derivatives Other current assets 582 (247 ) — 335 Other current liabilities 26,541 (52,004 ) 20,960 (4,503 ) Other non-current liabilities and deferred credits 3,996 (14,760 ) 5,214 (5,550 ) Total derivative instruments recorded on the balance sheet $ 32,554 $ (99,429 ) $ 31,204 $ (35,671 ) The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2018 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Asset Gross Liability Collateral Net Asset Foreign currency exchange derivatives Other current liabilities $ — $ (45 ) $ — $ (45 ) Interest rate swap derivatives Other current assets 5,283 — — 5,283 Other property and investments-net and other non-current assets 5,283 (440 ) — 4,843 Other non-current liabilities and deferred credits — (7,391 ) 530 (6,861 ) Energy commodity derivatives Other current assets 400 (130 ) — 270 Other current liabilities 31,457 (73,155 ) 37,790 (3,908 ) Other non-current liabilities and deferred credits 4,426 (21,292 ) 13,427 (3,439 ) Total derivative instruments recorded on the balance sheet $ 46,849 $ (102,453 ) $ 51,747 $ (3,857 ) Exposure to Demands for Collateral Avista Corp.'s derivative contracts often require collateral (in the form of cash or letters of credit) or other credit enhancements, or reductions or terminations of a portion of the contract through cash settlement. In the event of a downgrade in Avista Corp.'s credit ratings or changes in market prices, additional collateral may be required. In periods of price volatility, the level of exposure can change significantly. As a result, sudden and significant demands may be made against Avista Corp.'s credit facilities and cash. Avista Corp. actively monitors the exposure to possible collateral calls and takes steps to mitigate capital requirements. The following table presents Avista Corp.'s collateral outstanding related to its derivative instruments as of June 30, 2019 and December 31, 2018 (in thousands): June 30, December 31, 2019 2018 Energy commodity derivatives Cash collateral posted $ 26,174 $ 78,025 Letters of credit outstanding 14,600 6,500 Balance sheet offsetting (cash collateral against net derivative positions) 26,174 51,217 Interest rate swap derivatives Cash collateral posted 5,030 530 Balance sheet offsetting (cash collateral against net derivative positions) 5,030 530 Certain of Avista Corp.’s derivative instruments contain provisions that require Avista Corp. to maintain an "investment grade" credit rating from the major credit rating agencies. If Avista Corp.’s credit ratings were to fall below "investment grade," it would be in violation of these provisions, and the counterparties to the derivative instruments could request immediate payment or demand immediate and ongoing collateralization on derivative instruments in net liability positions. The following table presents the aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position and the amount of additional collateral Avista Corp. could be required to post as of June 30, 2019 and December 31, 2018 (in thousands): June 30, December 31, 2019 2018 Energy commodity derivatives Liabilities with credit-risk-related contingent features $ 1,564 $ 2,193 Additional collateral to post 1,563 2,193 Interest rate swap derivatives Liabilities with credit-risk-related contingent features 32,418 7,831 Additional collateral to post 25,986 6,579

Pension Plans And Other Postret

Pension Plans And Other Postretirement Benefit Plans	6 Months Ended
	Jun. 30, 2019
Retirement Benefits, Description [Abstract]
Pension Plans and Other Postretirement Benefit Plans	PENSION PLANS AND OTHER POSTRETIREMENT BENEFIT PLANS Avista Utilities Avista Utilities’ maintained the same pension and other postretirement plans during the six months ended June 30, 2019 as those described as of December 31, 2018. The Company’s funding policy is to contribute at least the minimum amounts that are required to be funded under the Employee Retirement Income Security Act, but not more than the maximum amounts that are currently deductible for income tax purposes. The Company contributed $14.6 million in cash to the pension plan for the six months ended June 30, 2019 and it expects to contribute a total of $22.0 million in 2019. 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 six months ended June 30 (dollars in thousands): Pension Benefits Other Postretirement Benefits 2019 2018 2019 2018 Three months ended June 30: Service cost (a) $ 4,948 $ 5,450 $ 753 $ 804 Interest cost 7,100 6,466 1,164 1,197 Expected return on plan assets (7,953 ) (8,250 ) (611 ) (500 ) Amortization of prior service cost 75 75 (275 ) 209 Net loss recognition 2,426 1,842 1,329 562 Net periodic benefit cost $ 6,596 $ 5,583 $ 2,360 $ 2,272 Six months ended June 30: Service cost (a) $ 9,822 $ 10,900 $ 1,525 $ 1,608 Interest cost 14,238 12,932 2,536 2,394 Expected return on plan assets (15,768 ) (16,500 ) (1,329 ) (1,000 ) Amortization of prior service cost 150 150 (550 ) (606 ) Net loss recognition 4,841 3,930 2,575 2,217 Net periodic benefit cost $ 13,283 $ 11,412 $ 4,757 $ 4,613 (a) Total service costs in the table above are recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses.

Income Taxes Income Taxes (Note

Income Taxes Income Taxes (Notes)	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Text Block]	INCOME TAXES The following table summarizes the significant factors impacting the difference between our effective tax rate and the federal statutory rate for the three and six months ended June 30 (dollars in thousands): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Federal income taxes at statutory rates $ 4,874 21.0 % $ 6,479 21.0 % $ 35,513 21.0 % $ 20,269 21.0 % Increase (decrease) in tax resulting from: Tax effect of regulatory treatment of utility plant differences (2,139 ) (9.2 ) (1,981 ) (6.4 ) (4,219 ) (2.5 ) (2,999 ) (3.1 ) State income tax expense (8 ) — 60 0.2 1,651 1.0 1,024 1.1 Acquisition costs 112 0.5 73 0.2 (1,712 ) (1.0 ) 119 0.1 Non-plant excess deferred turnaround (1) (5,091 ) (21.9 ) (11 ) — (5,601 ) (3.3 ) (11 ) — Tax loss on sale of METALfx (1,259 ) (5.4 ) — — (1,259 ) (0.8 ) — — Valuation allowance 1,245 5.3 — — 1,245 0.7 — — Settlement of equity awards — — — — 612 0.4 (990 ) (1.0 ) Other 525 2.2 589 1.9 2,046 1.2 (1,493 ) (1.6 ) Total income tax expense (benefit) $ (1,741 ) (7.5 )% $ 5,209 16.9 % $ 28,276 16.7 % $ 15,919 16.5 % (1) In March 2019, the IPUC approved an all-party settlement agreement related to electric tax benefits that were set aside for Colstrip in the 2017 general rate case order. In the approved settlement agreement, the parties agreed to utilize approximately $6.4 million ( $5.1 million when tax-effected) of the electric tax benefits to offset costs associated with accelerating the depreciation of Colstrip Units 3 & 4, to reflect a remaining useful life of those units through December 31, 2027. In the second quarter 2019, the Company recorded a one-time charge to depreciation expense with an offsetting amount included in income tax expense.

Committed Lines of Credit

Committed Lines of Credit	6 Months Ended
	Jun. 30, 2019
Short-term Debt [Abstract]
Committed Lines of Credit	COMMITTED LINES OF CREDIT Avista Corp. Avista Corp. has a committed line of credit with various financial institutions in the total amount of $400.0 million that expires in April 2021 . The committed line of credit is secured by non-transferable first mortgage bonds of the Company issued to the agent bank that would only become due and payable in the event, and then only to the extent, that the Company defaults on its obligations under the committed line of credit. Balances outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed line of credit were as follows as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Balance outstanding at end of period (1) $ 169,000 $ 190,000 Letters of credit outstanding at end of period $ 18,603 $ 10,503 Average interest rate at end of period 3.26 % 3.18 % (1) As of June 30, 2019 and December 31, 2018 , the balance outstanding was classified as short-term borrowings on the Condensed Consolidated Balance Sheet. AEL&P AEL&P has a committed line of credit in the amount of $25.0 million that expires in November 2019 . As of June 30, 2019 and December 31, 2018 , there were no borrowings or letters of credit outstanding under this committed line of credit. The committed line of credit is secured by non-transferable first mortgage bonds of AEL&P issued to the agent bank that would only become due and payable in the event, and then only to the extent, that AEL&P defaults on its obligations under the committed line of credit.

Long- Term Debt to Affiliated T

Long- Term Debt to Affiliated Trust Long-Term Debt to Affiliated Trust (Notes)	6 Months Ended
	Jun. 30, 2019
Long-Term Debt to Affiliated Trust [Abstract]
Long Term Debt To Affiliated Trusts Disclosure [Text Block]	LONG-TERM DEBT TO AFFILIATED TRUSTS In 1997, the Company issued Floating Rate Junior Subordinated Deferrable Interest Debentures, Series B, with a principal amount of $51.5 million to Avista Capital II, an affiliated business trust formed by the Company. Avista Capital II issued $50.0 million of Preferred Trust Securities with a floating distribution rate of LIBOR plus 0.875 percent , calculated and reset quarterly. The distribution rates paid were as follows during the six months ended June 30, 2019 and the year ended December 31, 2018 : June 30, December 31, 2019 2018 Low distribution rate 3.40 % 2.36 % High distribution rate 3.50 % 3.61 % Distribution rate at the end of the period 3.40 % 3.61 % Concurrent with the issuance of the Preferred Trust Securities, Avista Capital II issued $1.5 million of Common Trust Securities to the Company. The Preferred Trust Securities may be redeemed at the option of Avista Capital II at any time and mature on June 1, 2037. In December 2000, the Company purchased $10.0 million of these Preferred Trust Securities. The Company owns 100 percent of Avista Capital II and has solely and unconditionally guaranteed the payment of distributions on, and redemption price and liquidation amount for, the Preferred Trust Securities to the extent that Avista Capital II has funds available for such payments from the respective debt securities. Upon maturity or prior redemption of such debt securities, the Preferred Trust Securities will be mandatorily redeemed. The Company does not include these capital trusts in its consolidated financial statements as Avista Corp. is not the primary beneficiary. As such, the sole assets of the capital trusts are $51.5 million of junior subordinated deferrable interest debentures of Avista Corp., which are reflected on the Condensed Consolidated Balance Sheets. Interest expense to affiliated trusts in the Condensed Consolidated Statements of Income represents interest expense on these debentures.

Fair Value

Fair Value	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value	FAIR VALUE The carrying values of cash and cash equivalents, accounts and notes receivable, accounts payable, and short-term borrowings are reasonable estimates of their fair values. Long-term debt (including current portion and material capital leases) and long-term debt to affiliated trusts are reported at carrying value on the Condensed Consolidated Balance Sheets. The fair value hierarchy prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to fair values derived from unobservable inputs (Level 3 measurement). The three levels of the fair value hierarchy are defined as follows: Level 1 – Quoted prices are available in active markets for identical assets or liabilities. Active markets are those in which transactions for the asset or liability occur with sufficient frequency and volume to provide pricing information on an ongoing basis. Level 2 – Pricing inputs are other than quoted prices in active markets included in Level 1, but which are either directly or indirectly observable as of the reporting date. Level 2 includes those financial instruments that are valued using models or other valuation methodologies. These models are primarily industry-standard models that consider various assumptions, including quoted forward prices for commodities, time value, volatility factors, and current market and contractual prices for the underlying instruments, as well as other relevant economic measures. Substantially all of these assumptions are observable in the marketplace throughout the full term of the instrument, can be derived from observable data or are supported by observable levels at which transactions are executed in the marketplace. Level 3 – Pricing inputs include significant inputs that are generally unobservable from objective sources. These inputs may be used with internally developed methodologies that result in management’s best estimate of fair value. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy levels. The determination of the fair values incorporates various factors that not only include the credit standing of the counterparties involved and the impact of credit enhancements (such as cash deposits and letters of credit), but also the impact of Avista Corp.’s nonperformance risk on its liabilities. The following table sets forth the carrying value and estimated fair value of the Company’s financial instruments not reported at estimated fair value on the Condensed Consolidated Balance Sheets as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, 2019 December 31, 2018 Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Long-term debt (Level 2) $ 1,053,500 $ 1,198,009 $ 1,053,500 $ 1,142,292 Long-term debt (Level 3) 767,000 762,204 767,000 734,742 Snettisham finance lease obligation (Level 3) 55,880 58,200 57,210 55,600 Long-term debt to affiliated trusts (Level 3) 51,547 39,691 51,547 38,145 These estimates of fair value of long-term debt and long-term debt to affiliated trusts were primarily based on available market information, which generally consists of estimated market prices from third party brokers for debt with similar risk and terms. The price ranges obtained from the third party brokers consisted of par values of 77.00 to 130.25 , where a par value of 100.0 represents the carrying value recorded on the Condensed Consolidated Balance Sheets. Level 2 long-term debt represents publicly issued bonds with quoted market prices; however, due to their limited trading activity, they are classified as Level 2 because brokers must generate quotes and make estimates if there is no trading activity near a period end. Level 3 long-term debt consists of private placement bonds and debt to affiliated trusts, which typically have no secondary trading activity. Fair values in Level 3 are estimated based on market prices from third party brokers using secondary market quotes for debt with similar risk and terms to generate quotes for Avista Corp. bonds. Due to the unique nature of the Snettisham capital lease obligation, the estimated fair value of these items was determined based on a discounted cash flow model using available market information. The Snettisham capital lease obligation was discounted to present value using the Morgan Markets A Ex-Fin discount rate as published on June 30, 2019 . 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 June 30, 2019 and December 31, 2018 at fair value on a recurring basis (dollars in thousands): Level 1 Level 2 Level 3 Counterparty Total June 30, 2019 Assets: Energy commodity derivatives $ — $ 31,074 $ — $ (30,739 ) $ 335 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 45 (45 ) — Foreign currency exchange derivatives — 33 — — 33 Interest rate swap derivatives — 1,402 — (969 ) 433 Deferred compensation assets: Mutual Funds: Fixed income securities (2) 1,787 — — — 1,787 Equity securities (2) 6,325 — — — 6,325 Total $ 8,112 $ 32,509 $ 45 $ (31,753 ) $ 8,913 Liabilities: Energy commodity derivatives $ — $ 63,974 $ — $ (56,913 ) $ 7,061 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 3,037 (45 ) 2,992 Interest rate swap derivatives — 32,418 — (5,999 ) 26,419 Total $ — $ 96,392 $ 3,037 $ (62,957 ) $ 36,472 Level 1 Level 2 Level 3 Counterparty Total December 31, 2018 Assets: Energy commodity derivatives $ — $ 36,252 $ — $ (35,982 ) $ 270 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 31 (31 ) — Interest rate swap derivatives — 10,566 — (440 ) 10,126 Deferred compensation assets: Mutual Funds: Fixed income securities (2) 1,745 — — — 1,745 Equity securities (2) 6,157 — — — 6,157 Total $ 7,902 $ 46,818 $ 31 $ (36,453 ) $ 18,298 Liabilities: Energy commodity derivatives $ — $ 89,283 $ — $ (87,199 ) $ 2,084 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 2,805 (31 ) 2,774 Power exchange agreement — — 2,488 — 2,488 Power option agreement — — 1 — 1 Foreign currency exchange derivatives — 45 — — 45 Interest rate swap derivatives — 7,831 — (970 ) 6,861 Total $ — $ 97,159 $ 5,294 $ (88,200 ) $ 14,253 (1) The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties. (2) These assets are included in other property and investments-net and other non-current assets on the Condensed Consolidated Balance Sheets. The difference between the amount of derivative assets and liabilities disclosed in respective levels in the table above and the amount of derivative assets and liabilities disclosed on the Condensed Consolidated Balance Sheets is due to netting arrangements with certain counterparties. See Note 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 US dollar and multiplies the difference between the locked-in price and the market price by the notional amount of the derivative. Forward foreign currency market curves are provided by third party brokers. The Company's credit spread is factored into the locked-in price of the foreign exchange contracts. Deferred compensation assets and liabilities represent funds held by the Company in a Rabbi Trust for an executive deferral plan. These funds consist of actively traded equity and bond funds with quoted prices in active markets. The balance disclosed in the table above excludes cash and cash equivalents of $0.4 million as of June 30, 2019 and $0.5 million as of December 31, 2018 . Level 3 Fair Value Under the power exchange agreement, which expired on June 30, 2019, the Company purchased power at a price that was based on the average operating and maintenance (O&M) charges from three surrogate nuclear power plants around the country. To estimate the fair value of this agreement, the Company estimated the difference between the purchase price based on the future O&M charges and forward prices for energy. The Company compared the Level 2 brokered quotes and forward price curves described above to an internally developed forward price which was based on the average O&M charges from the three surrogate nuclear power plants for the current year. The Company estimated the volumes of the transactions that would take place in the future based on historical average transaction volumes per delivery year (November to April). Significant increases or decreases in any of these inputs in isolation would result in a significantly higher or lower fair value measurement. For the natural gas commodity exchange agreement, the Company uses the same Level 2 brokered quotes described above; however, the Company also estimates the purchase and sales volumes (within contractual limits) as well as the timing of those transactions. Changing the timing of volume estimates changes the timing of purchases and sales, impacting which brokered quote is used. Because the brokered quotes can vary significantly from period to period, the unobservable estimates of the timing and volume of transactions can have a significant impact on the calculated fair value. The Company currently estimates volumes and timing of transactions based on a most likely scenario using historical data. Historically, the timing and volume of transactions have not been highly correlated with market prices and market volatility. The following table presents the quantitative information which was used to estimate the fair values of the Level 3 assets and liabilities above as of June 30, 2019 (dollars in thousands): Fair Value (Net) at June 30, 2019 Valuation Technique Unobservable Input Range Natural gas exchange agreement $ (2,992 ) Internally derived Forward purchase prices $1.37 - $2.30/mmBTU Forward sales prices $1.45 - $3.62/mmBTU Purchase volumes 118,162 - 310,000 mmBTUs Sales volumes 60,000 - 310,000 mmBTUs The valuation methods, significant inputs and resulting fair values described above were developed by the Company's management and are reviewed on at least a quarterly basis to ensure they provide a reasonable estimate of fair value each reporting period. The following table presents activity for energy commodity derivative assets (liabilities) measured at fair value using significant unobservable inputs (Level 3) for the three and six months ended June 30 (dollars in thousands): Natural Gas Exchange Agreement Power Exchange Agreement Total Three months ended June 30, 2019: Balance as of April 1, 2019 $ (2,104 ) $ (612 ) $ (2,716 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities (1) (829 ) 1,454 625 Settlements (59 ) (842 ) (901 ) Ending balance as of June 30, 2019 (2) $ (2,992 ) $ — $ (2,992 ) Natural Gas Exchange Agreement Power Exchange Agreement Total Three months ended June 30, 2018: Balance as of April 1, 2018 $ (2,805 ) $ (10,163 ) $ (12,968 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities (1) (768 ) 2,597 1,829 Settlements 93 1,221 1,314 Ending balance as of June 30, 2018 (2) $ (3,480 ) $ (6,345 ) $ (9,825 ) Six months ended June 30, 2019: Balance as of January 1, 2019 $ (2,774 ) $ (2,488 ) $ (5,262 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities (1) 8,148 436 8,584 Settlements (8,366 ) 2,052 (6,314 ) Ending balance as of June 30, 2019 (2) $ (2,992 ) $ — $ (2,992 ) Six months ended June 30, 2018: Balance as of January 1, 2018 $ (3,164 ) $ (13,245 ) $ (16,409 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities (1) (565 ) 720 155 Settlements 249 6,180 6,429 Ending balance as of June 30, 2018 (2) $ (3,480 ) $ (6,345 ) $ (9,825 ) (1) All gains and losses are included in other regulatory assets and liabilities. There were no gains and losses included in either net income or other comprehensive income during any of the periods presented in the table above. (2) There were no purchases, issuances or transfers from other categories of any derivatives instruments during the periods presented in the table above.

Common Stock Common Stock (Note

Common Stock Common Stock (Notes)	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	COMMON STOCK The Company has entered into four separate sales agency agreements under which the sales agents may offer and sell new shares of the Company’s common stock from time to time. During the three and six months ended June 30, 2019 the Company issued 0.4 million shares under the sales agency agreements. These agreements provide for the offering of a maximum of approximately 4.6 million shares, of which approximately 4.2 million remain unissued as of June 30, 2019 . Subject to the satisfaction of customary conditions, the Company has the right to increase the maximum number of shares that may be offered under these agreements subject to regulatory approval. Accumulated other comprehensive loss, net of tax, consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $2,006 and $2,091, respectively $ 7,545 $ 7,866 The following table details the reclassifications out of accumulated other comprehensive loss to net income by component for the three and six months ended June 30 (dollars in thousands). Amounts Reclassified from Accumulated Other Comprehensive Loss Three months ended June 30, Six months ended June 30, Details about Accumulated Other Comprehensive Loss Components 2019 2018 2019 2018 Affected Line Item in Statement of Income Amortization of defined benefit pension items Amortization of net prior service cost $ (200 ) $ (228 ) $ (400 ) $ (456 ) (a) Amortization of net loss 3,755 2,995 7,416 5,990 (a) Adjustment due to effects of regulation (3,352 ) (2,509 ) (6,610 ) (5,017 ) (a) 203 258 406 517 Total before tax (42 ) (54 ) (85 ) (109 ) Tax expense $ 161 $ 204 $ 321 $ 408 Net of tax (a) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details).

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss (Notes)	6 Months Ended
	Jun. 30, 2019
Accumulated Other Comprehensive Loss [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	COMMON STOCK The Company has entered into four separate sales agency agreements under which the sales agents may offer and sell new shares of the Company’s common stock from time to time. During the three and six months ended June 30, 2019 the Company issued 0.4 million shares under the sales agency agreements. These agreements provide for the offering of a maximum of approximately 4.6 million shares, of which approximately 4.2 million remain unissued as of June 30, 2019 . Subject to the satisfaction of customary conditions, the Company has the right to increase the maximum number of shares that may be offered under these agreements subject to regulatory approval. Accumulated other comprehensive loss, net of tax, consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $2,006 and $2,091, respectively $ 7,545 $ 7,866 The following table details the reclassifications out of accumulated other comprehensive loss to net income by component for the three and six months ended June 30 (dollars in thousands). Amounts Reclassified from Accumulated Other Comprehensive Loss Three months ended June 30, Six months ended June 30, Details about Accumulated Other Comprehensive Loss Components 2019 2018 2019 2018 Affected Line Item in Statement of Income Amortization of defined benefit pension items Amortization of net prior service cost $ (200 ) $ (228 ) $ (400 ) $ (456 ) (a) Amortization of net loss 3,755 2,995 7,416 5,990 (a) Adjustment due to effects of regulation (3,352 ) (2,509 ) (6,610 ) (5,017 ) (a) 203 258 406 517 Total before tax (42 ) (54 ) (85 ) (109 ) Tax expense $ 161 $ 204 $ 321 $ 408 Net of tax (a) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details).

Earnings Per Common Share Attri

Earnings Per Common Share Attributable To Avista Corporation	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Common Share Attributable To Avista Corporation Shareholders	EARNINGS PER COMMON SHARE ATTRIBUTABLE TO AVISTA CORP. SHAREHOLDERS The following table presents the computation of basic and diluted earnings per common share attributable to Avista Corp. shareholders for the three and six months ended June 30 (in thousands, except per share amounts): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Numerator: Net income attributable to Avista Corp. shareholders $ 25,319 $ 25,577 $ 141,113 $ 80,467 Denominator: Weighted-average number of common shares outstanding-basic 65,894 65,677 65,814 65,658 Effect of dilutive securities: Performance and restricted stock awards 69 306 69 299 Weighted-average number of common shares outstanding-diluted 65,963 65,983 65,883 65,957 Earnings per common share attributable to Avista Corp. shareholders: Basic $ 0.38 $ 0.39 $ 2.14 $ 1.23 Diluted $ 0.38 $ 0.39 $ 2.14 $ 1.22

Commitments And Contingencies

Commitments And Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	COMMITMENTS AND CONTINGENCIES In the course of its business, the Company becomes involved in various claims, controversies, disputes and other contingent matters, including the items described in this Note. Some of these claims, controversies, disputes and other contingent matters involve litigation or other contested proceedings. For all such matters, the Company intends to vigorously protect and defend its interests and pursue its rights. However, no assurance can be given as to the ultimate outcome of any particular matter because litigation and other contested proceedings are inherently subject to numerous uncertainties. For matters that affect Avista Utilities’ or AEL&P's operations, the Company intends to seek, to the extent appropriate, recovery of incurred costs through the ratemaking process. Cabinet Gorge Total Dissolved Gas Abatement Plan Dissolved atmospheric gas levels (referred to as "Total Dissolved Gas" or "TDG") in the Clark Fork River exceed state of Idaho and federal water quality numeric standards downstream of Cabinet Gorge particularly during periods when excess river flows must be diverted over the spillway. Under the terms of the Clark Fork Settlement Agreement (CFSA) as incorporated in Avista Corp.’s FERC license for the Clark Fork Project, Avista Corp. has worked in consultation with agencies, tribes and other stakeholders to address this issue. Under the terms of a gas supersaturation mitigation plan, Avista Corp. is reducing TDG by constructing spill crest modifications on spill gates at the dam. These modifications have been shown to be effective in reducing TDG downstream. TDG monitoring and analysis is ongoing. Under the terms of the mitigation plan, Avista Corp. will continue to work with stakeholders to determine the degree to which TDG abatement reduces future mitigation obligations. The Company has sought, and will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to this issue. Legal Proceedings Related to the Terminated Acquisition by Hydro One See Note 17 for information regarding the termination of the proposed acquisition of the Company by Hydro One. In connection with the now terminated acquisition, three lawsuits were filed in the United States District Court for the Eastern District of Washington and were subsequently voluntarily dismissed by the plaintiffs. One lawsuit was filed in the Superior Court for the State of Washington in and for Spokane County, captioned as follows: • Fink v. Morris, et al., No. 17203616-6 (filed September 15, 2017, amended complaint filed October 25, 2017). The complaint generally alleged that the members of the Board of Directors of Avista Corp. breached their fiduciary duties by, among other things, conducting an allegedly inadequate sale process and agreeing to the acquisition at a price that allegedly undervalued Avista Corporation, and that Hydro One Limited, Olympus Holding Corp., and Olympus Corp. aided and abetted those purported breaches of duty. The complaint sought various remedies, including monetary damages, attorneys’ fees and expenses. Subsequent to the termination of the proposed acquisition in January 2019, the complaint was voluntarily dismissed by the plaintiffs. 2015 Washington General Rate Cases In January 2016, the Company received an order (Order 05) that concluded its electric and natural gas general rate cases that were originally filed with the WUTC in February 2015. New electric and natural gas rates were effective on January 11, 2016. WUTC Order Denying Industrial Customers of Northwest Utilities / Public Counsel Joint Motion for Clarification, WUTC Staff Motion to Reconsider and WUTC Staff Motion to Reopen Record In January 2016, the Industrial Customers of Northwest Utilities, the Public Counsel Unit of the Washington State Office of the Attorney General (PC) and the WUTC Staff, which is a separate party in the general rate case proceedings from the WUTC Advisory Staff, filed Motions for Clarification requesting the WUTC to clarify their attrition adjustment and the end result electric revenue amounts. The Motions for Clarification suggested that the electric revenue decrease should have been significantly larger than what was included in Order 05. In February 2016, the WUTC issued an order (Order 06) denying the Motions summarized above and affirming Order 05, including an $8.1 million decrease in electric base revenue. PC Petition for Judicial Review In March 2016, PC filed in Thurston County Superior Court a Petition for Judicial Review of the WUTC's Order 05 and Order 06 described above. In April 2016, this matter was certified for review directly by the Court of Appeals, an intermediate appellate court in the State of Washington. On August 7, 2018, the Court of Appeals issued a "Published Opinion" (Opinion) which concluded that the WUTC's use of an attrition allowance to calculate Avista Corp.'s rate base violated Washington law. In the Opinion, the Court stated that because the projected additions to rate base in the future were not "used and useful" for service at the time the request for the rate increase was made, they may not lawfully be included in the Company's rate base to justify a rate increase. Accordingly, the Court concluded that the WUTC erred in including an attrition allowance in the calculation of Avista Corp.’s electric and natural gas rate base. The Court noted, however, that the law does not prohibit an attrition allowance in the calculation, for ratemaking purposes, of recoverable operating and maintenance expense. Since the WUTC order provided one lump sum attrition allowance without distinguishing what portion was for rate base and which was for operating and maintenance expenses or other considerations, the Court struck all portions of the attrition allowance attributable to Avista Corp.'s rate base and reversed and remanded the case for the WUTC to recalculate Avista Corp.’s rates without including an attrition allowance in the calculation of rate base. On October 1, 2018, the Court of Appeals terminated its review of this case, remanding it back to the Thurston County Superior Court. On April 17, 2019, the Thurston County Superior Court issued a Remand Order, granting a Joint Motion of Avista Corp., PC and the WUTC to remand the case back to the WUTC. On June 20, 2019, Avista Corp. filed testimony with the WUTC in the remand case. In Avista Corp.'s testimony, it asserted that the potential amount to return to customers is limited to the 2015 general rate cases because in subsequent Washington general rate cases (specifically those approved in December 2016), the WUTC did not include any attrition allowance on rate base. In the remand testimony the Company also asserted that no refund is due to customers for the 2015 general rate cases because actual 2016 electric rate base was greater than the 2016 electric rate base allowed in the general rate case, which included an attrition allowance. In addition, while 2016 actual natural gas rate base was slightly lower than the rate base allowed in the general rate case including the attrition allowance, any over-earnings were offset by the earnings sharing mechanism that allowed for a refund to customers. Even though the Company believes the issue only relates to the 2015 general rate cases and no refund is due to customers, the Company cannot predict the outcome of this matter at this time and cannot estimate how much, if any, it could be required to refund to customers. Other Contingencies In the normal course of business, the Company has various other legal claims and contingent matters outstanding. The Company believes that any ultimate liability arising from these actions will not have a material impact on its financial condition, results of operations or cash flows. It is possible that a change could occur in the Company’s estimates of the probability or amount of a liability being incurred. Such a change, should it occur, could be significant. See "Note 20 of the Notes to Consolidated Financial Statements" in the 2018 Form 10-K for additional discussion regarding other contingencies.

Information By Business Segment

Information By Business Segments	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Information by Business Segments	INFORMATION BY BUSINESS SEGMENTS The business segment presentation reflects the basis used by the Company's management to analyze performance and determine the allocation of resources. The Company's management evaluates performance based on income (loss) from operations before income taxes as well as net income (loss) attributable to Avista Corp. shareholders. The accounting policies of the segments are the same as those described in the summary of significant accounting policies. Avista Utilities' business is managed based on the total regulated utility operation; therefore, it is considered one segment. AEL&P is a separate reportable business segment, as it has separate financial reports that are reviewed in detail by the Chief Operating Decision Maker and its operations and risks are sufficiently different from Avista Utilities and the other businesses at AERC that it cannot be aggregated with any other operating segments. The Other category, which is not a reportable segment, includes other investments and operations of various subsidiaries, as well as certain other operations of Avista Capital. The following table presents information for each of the Company’s business segments (dollars in thousands): Avista Utilities Alaska Electric Light and Power Company Total Utility Other Intersegment Eliminations (1) Total For the three months ended June 30, 2019: Operating revenues $ 289,808 $ 8,743 $ 298,551 $ 2,261 $ — $ 300,812 Resource costs 88,506 (67 ) 88,439 — — 88,439 Other operating expenses (2) 84,602 3,129 87,731 6,332 — 94,063 Depreciation and amortization 53,070 2,409 55,479 155 — 55,634 Income (loss) from operations 40,978 3,016 43,994 (4,226 ) — 39,768 Interest expense (3) 24,316 1,595 25,911 148 (197 ) 25,862 Income taxes (2,947 ) 380 (2,567 ) 826 — (1,741 ) Net income attributable to Avista Corp. shareholders 21,219 1,076 22,295 3,024 — 25,319 Capital expenditures (4) 103,297 3,076 106,373 22 — 106,395 For the three months ended June 30, 2018: Operating revenues $ 302,222 $ 10,482 $ 312,704 $ 6,594 $ — $ 319,298 Resource costs 103,022 2,947 105,969 — — 105,969 Other operating expenses (2) (5) 78,848 3,213 82,061 6,543 — 88,604 Depreciation and amortization 44,186 1,465 45,651 199 — 45,850 Income (loss) from operations (5) 50,848 2,579 53,427 (148 ) — 53,279 Interest expense (3) 24,428 896 25,324 382 (234 ) 25,472 Income taxes 4,735 446 5,181 28 — 5,209 Net income attributable to Avista Corp. shareholders 24,252 1,282 25,534 43 — 25,577 Capital expenditures (4) 97,963 3,352 101,315 338 — 101,653 Avista Utilities Alaska Electric Light and Power Company Total Utility Other Intersegment Eliminations (1) Total For the six months ended June 30, 2019: Operating revenues $ 667,510 $ 19,624 $ 687,134 $ 10,159 $ — $ 697,293 Resource costs 227,218 (1,432 ) 225,786 — — 225,786 Other operating expenses (2) 185,185 6,188 191,373 13,687 — 205,060 Depreciation and amortization 99,577 4,816 104,393 364 — 104,757 Income (loss) from operations 101,202 9,529 110,731 (3,892 ) — 106,839 Interest expense (3) 48,580 3,191 51,771 736 (637 ) 51,870 Income taxes 25,597 1,743 27,340 936 — 28,276 Net income attributable to Avista Corp. shareholders 133,120 4,628 137,748 3,365 — 141,113 Capital expenditures (4) 195,606 4,382 199,988 184 — 200,172 For the six months ended June 30, 2018: Operating revenues $ 690,976 $ 24,145 $ 715,121 $ 13,538 $ — $ 728,659 Resource costs 254,687 5,900 260,587 — — 260,587 Other operating expenses (2) 153,987 6,044 160,031 13,367 — 173,398 Depreciation and amortization 87,453 2,931 90,384 380 — 90,764 Income (loss) from operations 138,993 8,701 147,694 (209 ) — 147,485 Interest expense (3) 48,393 1,790 50,183 717 (399 ) 50,501 Income taxes 15,152 1,910 17,062 (1,143 ) — 15,919 Net income (loss) attributable to Avista Corp. shareholders 79,792 5,054 84,846 (4,379 ) — 80,467 Capital expenditures (4) 179,139 3,993 183,132 552 — 183,684 Total Assets: As of June 30, 2019: $ 5,520,529 $ 277,934 $ 5,798,463 $ 107,753 $ (28,288 ) $ 5,877,928 As of December 31, 2018: $ 5,458,104 $ 272,950 $ 5,731,054 $ 87,050 $ (35,528 ) $ 5,782,576 (1) Intersegment eliminations reported as interest expense represent intercompany interest. (2) Other operating expenses for Avista Utilities for the three and six months ended June 30 , 2019 and 2018 include merger transaction costs which are separately disclosed on the Condensed Consolidated Statements of Income. (3) Including interest expense to affiliated trusts. (4) The capital expenditures for the other businesses are included in other investing activities on the Condensed Consolidated Statements of Cash Flows.

Termination of Proposed Acquisi

Termination of Proposed Acquisition by Hydro One Termination of Proposed Acquisition by Hydro One (Notes)	6 Months Ended
	Jun. 30, 2019
Business Acquisition [Line Items]
Business Combination Disclosure [Text Block]	On July 19, 2017, Avista Corp. entered into a Merger Agreement that provided for Avista Corp. to become an indirect, wholly-owned subsidiary of Hydro One, subject to the satisfaction or waiver of specified closing conditions, including approval by regulatory agencies. Hydro One, based in Toronto, is Ontario’s largest electricity transmission and distribution provider. Termination of the Merger Agreement Due to the denial of the proposed merger by certain of the Company's regulatory commissions, on January 23, 2019, Avista Corp., Hydro One and certain subsidiaries thereof, entered into a Termination Agreement indicating their mutual agreement to terminate the Merger Agreement, effective immediately. Pursuant to the terms of the Termination Agreement, Hydro One paid Avista Corp. a $103 million termination fee on January 24, 2019. The termination fee was used for reimbursing the Company's transaction costs incurred from 2017 to 2019. The balance of the termination fee remaining after payment of 2019 transaction costs and applicable income taxes was used for general corporate purposes and reduced the Company's need for external financing. The 2019 costs totaled $19.7 million pre-tax and included financial advisers' fees, legal fees, consulting fees and employee time. Other Information Related to the Terminated Acquisition Due to the termination of the acquisition, all the financial commitments that were included in the various settlement agreements with the commissions for the proposed acquisition will not be required to be performed or observed. The Company incurred significant transaction costs consisting primarily of consulting, banking fees, legal fees and employee time, and these costs are not being passed through to customers. When the Company was assuming the transaction was going to be completed, a significant portion of these costs were not deductible for income tax purposes. Now that the transaction has been terminated, the Company expects more of the previously incurred transaction costs to be deductible so it expects additional tax benefits from these costs in 2019. See Note 15 for discussion of shareholder lawsuits filed against the Company, the Company’s directors, Hydro One, Olympus Holding Corp., and Olympus Corp. in relation to the Merger Agreement and the proposed acquisition.

Sale of METALfx Sale of METALfx

Sale of METALfx Sale of METALfx (Notes)	6 Months Ended
	Jun. 30, 2019
Assets Held for Sale [Abstract]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	SALE OF METALfx In April 2019, Bay Area Manufacturing, Inc., a non-regulated subsidiary of Avista Corp., entered into a definitive agreement to sell its interest in METALfx to an independent third party. The transaction was a stock sale for a total cash purchase price of $17.5 million plus cash on-hand, subject to customary closing adjustments. The transaction closed on April 18, 2019, and as of that date the Company has no further involvement with METALfx. The purchase price of $17.5 million , as adjusted, was divided among the security holders of METALfx, including the minority shareholder, pro rata based on ownership (Avista Corp. owned 89.2 percent of the equity of METALfx). As required under the purchase agreement, $1.2 million ( 7 percent of the purchase price) will be held in escrow for 24 months from the closing of the transaction to satisfy certain indemnification obligations. When all escrow amounts are released, the sales transaction is expected to provide cash proceeds to Avista Corp., net of payments to the minority holder, contractually obligated compensation payments and other transaction expenses, of $16.5 million and result in a net gain after-tax of $2.3 million . The Company expects to receive the full amount of its portion of the escrow accounts; therefore, the full amounts are included in the gain calculation. The gross gain is included in "Other income," the transaction expenses paid are included in "Non-utility Other operating expenses" and any taxes associated with the sale are included in "Income tax expense" on the Condensed Consolidated Statements of Income. Prior to the completion of the sales transaction, METALfx was not a reportable business segment and was included in other in the business segment footnote at Note 16. This transaction does not meet the criteria for discontinued operations as it does not represent a strategic shift that will have a major effect on the Company's ongoing operations,

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policy)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Nature Of Business	Nature of Business Avista Corp. is primarily an electric and natural gas utility with certain other business ventures. Avista Utilities is an operating division of Avista Corp., comprising its regulated utility operations in the Pacific Northwest. Avista Utilities provides electric distribution and transmission, and natural gas distribution services in parts of eastern Washington and northern Idaho. Avista Utilities also provides natural gas distribution service in parts of northeastern and southwestern Oregon. Avista Utilities has electric generating facilities in Washington, Idaho, Oregon and Montana. Avista Utilities also supplies electricity to a small number of customers in Montana, most of whom are employees who operate the Company's Noxon Rapids generating facility. AERC is a wholly-owned subsidiary of Avista Corp. The primary subsidiary of AERC is AEL&P, which comprises Avista Corp.'s regulated utility operations in Alaska. Avista Capital, a wholly owned non-regulated subsidiary of Avista Corp., is the parent company of all of the subsidiary companies in the non-utility businesses, with the exception of AJT Mining Properties, Inc., which is a subsidiary of AERC. See Note 16 for business segment information. See Note 18 for discussion of the sale of METALfx, an unregulated subsidiary of the Company.
Basis Of Reporting	Basis of Reporting The condensed consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Intercompany balances were eliminated in consolidation. The accompanying condensed consolidated financial statements include the Company’s proportionate share of utility plant and related operations resulting from its interests in jointly owned plants.
Derivative Assets And Liabilities	Derivative Assets and Liabilities Derivatives are recorded as either assets or liabilities on the Condensed Consolidated Balance Sheets measured at estimated fair value. The WUTC and the IPUC issued accounting orders authorizing Avista Corp. to offset energy commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment is intended to defer the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. Realized benefits and costs result in adjustments to retail rates through PGAs, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rate cases. The resulting regulatory assets associated with energy commodity derivative instruments have been concluded to be probable of recovery through future rates. Substantially all forward contracts to purchase or sell power and natural gas are recorded as derivative assets or liabilities at estimated fair value with an offsetting regulatory asset or liability. Contracts that are not considered derivatives are accounted for on the accrual basis until they are settled or realized unless there is a decline in the fair value of the contract that is determined to be other-than-temporary. For interest rate swap derivatives, Avista Corp. records all mark-to-market gains and losses in each accounting period as assets and liabilities, as well as offsetting regulatory assets and liabilities, such that there is no income statement impact. The interest rate swap derivatives are risk management tools similar to energy commodity derivatives. Upon settlement of interest rate swap derivatives, the 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, as well as derivatives related to interest rate swaps and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 11 for the Company’s fair value disclosures.
Contingencies	Contingencies The Company has unresolved regulatory, legal and tax issues which have inherently uncertain outcomes. The Company accrues a loss contingency if it is probable that a liability has been incurred and the amount of the loss or impairment can be reasonably estimated. The Company also discloses loss contingencies that do not meet these conditions for accrual if there is a reasonable possibility that a material loss may be incurred. As of June 30, 2019 , the Company has not recorded any significant amounts related to unresolved contingencies. See Note 15 for further discussion of the Company's commitments and contingencies.

Balance Sheet Components Bala_2

Balance Sheet Components Balance Sheet Components (Policies)	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Inventory, Policy [Policy Text Block]	Inventories of materials and supplies, fuel stock and stored natural gas are recorded at average cost for our regulated operations and the lower of cost or market for our non-regulated operations and consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Materials and supplies $ 46,886 $ 47,403 Fuel stock 6,332 4,869 Stored natural gas 14,441 11,609 Total $ 67,659 $ 63,881

Revenue Revenue (Policies)

Revenue Revenue (Policies)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue Recognition, Policy [Policy Text Block]	Utility Revenues Revenue from Contracts with Customers General The majority of Avista Corp.’s revenue is from rate-regulated sales of electricity and natural gas to retail customers, which has two performance obligations, (1) having service available for a specified period (typically a month at a time) and (2) the delivery of energy to customers. The total energy price generally has a fixed component (basic charge) related to having service available and a usage-based component, related to the delivery and consumption of energy. The commodity is sold and/or delivered to and consumed by the customer simultaneously, and the provisions of the relevant utility commission authorization determine the charges the Company may bill the customer. Given that all revenue recognition criteria are met upon the delivery of energy to customers, revenue is recognized immediately at that time. Revenues from contracts with customers are presented in the Condensed Consolidated Statements of Income in the line item "Utility revenues, exclusive of alternative revenue programs." Non-Derivative Wholesale Contracts The Company has certain wholesale contracts which are not accounted for as derivatives and, accordingly, are within the scope of ASC 606 and considered revenue from contracts with customers. Revenue is recognized as energy is delivered to the customer or the service is available for a specified period of time, consistent with the discussion of rate-regulated sales above. Alternative Revenue Programs (Decoupling) ASC 606 retained existing GAAP associated with alternative revenue programs, which specified that alternative revenue programs are contracts between an entity and a regulator of utilities, not a contract between an entity and a customer. GAAP requires that an entity present revenue arising from alternative revenue programs separately from revenues arising from contracts with customers on the face of the Condensed Consolidated Statements of Income. The Company's decoupling mechanisms (also known as a FCA in Idaho) qualify as alternative revenue programs. Decoupling revenue deferrals are recognized in the Condensed Consolidated Statements of Income during the period they occur (i.e. during the period of revenue shortfall or excess due to fluctuations in customer usage), subject to certain limitations, and a regulatory asset or liability is established that will be surcharged or rebated to customers in future periods. GAAP requires that for any alternative revenue program, like decoupling, the revenue must be expected to be collected from customers within 24 months of the deferral to qualify for recognition in the current period Condensed Consolidated Statement of Income. Any amounts included in the Company's decoupling program that are not expected to be collected from customers within 24 months are not recorded in the financial statements until the period in which revenue recognition criteria are met. The amounts expected to be collected from customers within 24 months represents an estimate that must be made by the Company on an ongoing basis due to it being based on the volumes of electric and natural gas sold to customers on a go-forward basis. Derivative Revenue Most wholesale electric and natural gas transactions (including both physical and financial transactions), and the sale of fuel are considered derivatives, which are specifically scoped out of ASC 606. As such, these revenues are disclosed separately from revenue from contracts with customers. Revenue is recognized for these items upon the settlement/expiration of the derivative contract. Derivative revenue includes those transactions that are entered into and settled within the same month. Other Utility Revenue Other utility revenue includes rent, revenues from the lineman training school, sales of materials, late fees and other charges that do not represent contracts with customers. Other utility revenue also includes the provision for earnings sharing and the deferral and amortization of refunds to customers associated with the TCJA. This revenue is scoped out of ASC 606, as this revenue does not represent items where a customer is a party that has contracted with the Company to obtain goods or services that are an output of the Company’s ordinary activities in exchange for consideration. As such, these revenues are presented separately from revenue from contracts with customers. Other Considerations for Utility Revenues Gross Versus Net Presentation Revenues and resource costs from Avista Utilities’ settled energy contracts that are “booked out” (not physically delivered) are reported on a net basis as part of derivative revenues. Utility-related taxes collected from customers (primarily state excise taxes and city utility taxes) are taxes that are imposed on Avista Utilities as opposed to being imposed on its customers; therefore, Avista Utilities is the taxpayer and records these transactions on a gross basis in revenue from contracts with customers and operating expense (taxes other than income taxes). The utility-related taxes collected from customers at AEL&P are imposed on the customers rather than AEL&P; therefore, the customers are the taxpayers and AEL&P is acting as their agent. As such, these transactions at AEL&P are presented on a net basis within revenue from contracts with customers. Utility-related taxes that were included in revenue from contracts with customers were as follows for the three and six months ended June 30 (dollars in thousands): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Utility-related taxes $ 12,688 $ 12,986 $ 31,777 $ 32,153 Non-Utility Revenues Revenue from Contracts with Customers Non-utility revenues from contracts with customers are primarily derived from the operations of METALfx (through the date of its sale in April 2019, see Note 18 for further discussion). The contracts associated with METALfx have one performance obligation, the delivery of a product, and revenues are recognized when the risk of loss transfers to the customer, which occurs when products are shipped. Significant Judgments and Unsatisfied Performance Obligations The only significant judgments involving revenue recognition are estimates surrounding unbilled revenue and receivables from contracts with customers and estimates surrounding the amount of decoupling revenues that will be collected from customers within 24 months (discussed above). The Company has certain capacity arrangements, where the Company has a contractual obligation to provide either electric or natural gas capacity to its customers for a fixed fee. Most of these arrangements are paid for in arrears by the customers and do not result in deferred revenue and only result in receivables from the customers. The Company does have one capacity agreement where the customer makes payments throughout the year and depending on the timing of the customer payments, it can result in an immaterial amount of deferred revenue or a receivable from the customer. As of June 30, 2019 , the Company estimates it had unsatisfied capacity performance obligations of $7.9 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.
Revenue Recognition for Alternative Revenue Programs, Policy [Policy Text Block]	Alternative Revenue Programs (Decoupling) ASC 606 retained existing GAAP associated with alternative revenue programs, which specified that alternative revenue programs are contracts between an entity and a regulator of utilities, not a contract between an entity and a customer. GAAP requires that an entity present revenue arising from alternative revenue programs separately from revenues arising from contracts with customers on the face of the Condensed Consolidated Statements of Income. The Company's decoupling mechanisms (also known as a FCA in Idaho) qualify as alternative revenue programs. Decoupling revenue deferrals are recognized in the Condensed Consolidated Statements of Income during the period they occur (i.e. during the period of revenue shortfall or excess due to fluctuations in customer usage), subject to certain limitations, and a regulatory asset or liability is established that will be surcharged or rebated to customers in future periods. GAAP requires that for any alternative revenue program, like decoupling, the revenue must be expected to be collected from customers within 24 months of the deferral to qualify for recognition in the current period Condensed Consolidated Statement of Income. Any amounts included in the Company's decoupling program that are not expected to be collected from customers within 24 months are not recorded in the financial statements until the period in which revenue recognition criteria are met. The amounts expected to be collected from customers within 24 months represents an estimate that must be made by the Company on an ongoing basis due to it being based on the volumes of electric and natural gas sold to customers on a go-forward basis.
Utility, Revenue and Expense Recognition, Policy [Policy Text Block]	Utility-related taxes collected from customers (primarily state excise taxes and city utility taxes) are taxes that are imposed on Avista Utilities as opposed to being imposed on its customers; therefore, Avista Utilities is the taxpayer and records these transactions on a gross basis in revenue from contracts with customers and operating expense (taxes other than income taxes). The utility-related taxes collected from customers at AEL&P are imposed on the customers rather than AEL&P; therefore, the customers are the taxpayers and AEL&P is acting as their agent. As such, these transactions at AEL&P are presented on a net basis within revenue from contracts with customers. Utility-related taxes that were included in revenue from contracts with customers were as follows for the three and six months ended June 30 (dollars in thousands): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Utility-related taxes $ 12,688 $ 12,986 $ 31,777 $ 32,153

Balance Sheet Components Bala_3

Balance Sheet Components Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of Other Current Assets [Table Text Block]	Other current assets consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Collateral posted for derivative instruments after netting with outstanding derivative liabilities $ — $ 26,809 Prepayments 24,515 17,536 Other 6,084 9,665 Total $ 30,599 $ 54,010
Schedule of Inventory, Current [Table Text Block]	Inventories of materials and supplies, fuel stock and stored natural gas are recorded at average cost for our regulated operations and the lower of cost or market for our non-regulated operations and consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Materials and supplies $ 46,886 $ 47,403 Fuel stock 6,332 4,869 Stored natural gas 14,441 11,609 Total $ 67,659 $ 63,881
Public Utility Property, Plant, and Equipment [Table Text Block]	Net utility property consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Utility plant in service $ 6,262,789 $ 6,209,968 Construction work in progress 191,845 160,598 Total 6,454,634 6,370,566 Less: Accumulated depreciation and amortization 1,769,980 1,721,636 Total net utility property $ 4,684,654 $ 4,648,930
Schedule of Other Current Assets [Table Text Block]	Other property and investments-net and other non-current assets consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Operating lease ROU assets $ 70,442 $ — Finance lease ROU assets 52,800 — Non-utility property 28,438 31,355 Equity investments 36,921 29,257 Investment in affiliated trust 11,547 11,547 Notes receivable 11,376 11,073 Deferred compensation assets 8,557 8,400 Other 20,549 23,065 Total $ 240,630 $ 114,697
Other Current Liabilities [Table Text Block]	Other current liabilities consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Accrued taxes other than income taxes $ 35,502 $ 36,858 Employee paid time off accruals 22,092 20,992 Accrued interest 16,536 16,704 Current portion of pensions and other postretirement benefits 11,175 9,151 Derivative liabilities 9,274 3,908 Other current liabilities 29,590 32,745 Total other current liabilities $ 124,169 $ 120,358
Other Noncurrent Liabilities [Table Text Block]	Other non-current liabilities and deferred credits consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Operating lease liabilities $ 68,228 $ — Finance lease liabilities 53,150 — Deferred investment tax credits 31,172 29,725 Asset retirement obligations 18,595 18,266 Derivative liabilities 27,198 10,300 Other 13,058 12,740 Total $ 211,401 $ 71,031
Schedule Of Regulated Asset And Liability [Table Text Block]	Regulatory assets and liabilities consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, 2019 December 31, 2018 Current Non-Current Current Non-Current Regulatory Assets Energy commodity derivatives $ 25,125 $ 10,764 $ 41,428 $ 16,866 Decoupling surcharge 6,498 16,167 3,408 17,501 Pension and other postretirement benefit plans — 221,454 — 228,062 Interest rate swaps — 155,787 — 133,854 Deferred income taxes — 95,217 — 91,188 Settlement with Coeur d'Alene Tribe — 41,988 — 42,643 Demand side management programs — 13,705 — 19,674 Utility plant to be abandoned — 25,273 — 24,334 Other regulatory assets 7,162 50,096 3,716 40,232 Total regulatory assets $ 38,785 $ 630,451 $ 48,552 $ 614,354 Regulatory Liabilities Income tax related liabilities $ 23,079 $ 418,039 $ 27,997 $ 425,613 Deferred natural gas costs 1,852 — 40,713 — Deferral power costs 6,612 32,617 25,072 16,933 Decoupling rebate 437 2,861 6,782 204 Utility plant retirement costs — 302,734 — 297,379 Interest rate swaps — 17,659 — 28,078 Other regulatory liabilities 5,974 15,745 12,645 12,494 Total regulatory liabilities $ 37,954 $ 789,655 $ 113,209 $ 780,701

Revenue Revenue (Tables)

Revenue Revenue (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue [Table Text Block]	Disaggregation of Total Operating Revenue The following table disaggregates total operating revenue by segment and source for the three and six months ended June 30 (dollars in thousands): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Avista Utilities Revenue from contracts with customers $ 231,605 $ 239,113 $ 585,907 $ 593,275 Derivative revenues 42,128 56,357 66,255 114,749 Alternative revenue programs 9,725 3,570 5,067 (2,369 ) Deferrals and amortizations for rate refunds to customers 2,512 982 4,647 (18,840 ) Other utility revenues 3,838 2,200 5,634 4,161 Total Avista Utilities 289,808 302,222 667,510 690,976 AEL&P Revenue from contracts with customers 8,620 10,759 19,356 25,409 Deferrals and amortizations for rate refunds to customers (47 ) (427 ) (95 ) (1,549 ) Other utility revenues 170 150 363 285 Total AEL&P 8,743 10,482 19,624 24,145 Other Revenue from contracts with customers 2,024 6,324 9,671 13,053 Other revenues 237 270 488 485 Total other 2,261 6,594 10,159 13,538 Total operating revenues $ 300,812 $ 319,298 $ 697,293 $ 728,659 Utility Revenue from Contracts with Customers by Type and Service The following table disaggregates revenue from contracts with customers associated with the Company's utility operations for the three and six months ended June 30 (dollars in thousands): 2019 2018 Avista Utilities AEL&P Total Utility Avista Utilities AEL&P Total Utility Three months ended June 30: ELECTRIC OPERATIONS Revenue from contracts with customers Residential $ 72,886 $ 3,724 $ 76,610 $ 74,818 $ 4,155 $ 78,973 Commercial and governmental 76,375 4,837 81,212 76,462 6,541 83,003 Industrial 26,245 — 26,245 27,985 — 27,985 Public street and highway lighting 1,897 59 1,956 1,899 63 1,962 Total retail revenue 177,403 8,620 186,023 181,164 10,759 191,923 Transmission 4,250 — 4,250 4,171 — 4,171 Other revenue from contracts with customers 4,379 — 4,379 3,919 — 3,919 Total revenue from contracts with customers $ 186,032 $ 8,620 $ 194,652 $ 189,254 $ 10,759 $ 200,013 NATURAL GAS OPERATIONS Revenue from contracts with customers Residential $ 27,937 $ — $ 27,937 $ 30,767 $ — $ 30,767 Commercial 13,369 — 13,369 14,668 — 14,668 Industrial and interruptible 1,103 — 1,103 1,078 — 1,078 Total retail revenue 42,409 — 42,409 46,513 — 46,513 Transportation 2,039 — 2,039 2,221 — 2,221 Other revenue from contracts with customers 1,125 — 1,125 1,125 — 1,125 Total revenue from contracts with customers $ 45,573 $ — $ 45,573 $ 49,859 $ — $ 49,859 Six months ended June 30: ELECTRIC OPERATIONS Residential $ 188,279 $ 9,576 $ 197,855 $ 189,571 $ 10,693 $ 200,264 Commercial and governmental 155,621 9,658 165,279 155,371 14,585 169,956 Industrial 51,493 — 51,493 53,104 — 53,104 Public street and highway lighting 3,800 122 3,922 3,758 131 3,889 Total retail revenue 399,193 19,356 418,549 401,804 25,409 427,213 Transmission 9,402 — 9,402 8,001 — 8,001 Other revenue from contracts with customers 12,573 — 12,573 10,210 — 10,210 Total electric revenue from contracts with customers $ 421,168 $ 19,356 $ 440,524 $ 420,015 $ 25,409 $ 445,424 2019 2018 Avista Utilities AEL&P Total Utility Avista Utilities AEL&P Total Utility NATURAL GAS OPERATIONS Residential $ 105,272 $ — $ 105,272 $ 111,421 $ — $ 111,421 Commercial 49,964 — 49,964 52,040 — 52,040 Industrial and interruptible 2,730 — 2,730 2,761 — 2,761 Total retail revenue 157,966 — 157,966 166,222 — 166,222 Transportation 4,523 — 4,523 4,788 — 4,788 Other revenue from contracts with customers 2,250 — 2,250 2,250 — 2,250 Total natural gas revenue from contracts with customers $ 164,739 $ — $ 164,739 $ 173,260 $ — $ 173,260
Schedule Of Utilities Operating Revenue Expense Taxes [Table Text Block]	Utility-related taxes that were included in revenue from contracts with customers were as follows for the three and six months ended June 30 (dollars in thousands): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Utility-related taxes $ 12,688 $ 12,986 $ 31,777 $ 32,153

Leases Leases (Tables)

Leases Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Lease, Cost [Table Text Block]	The components of lease expense were as follows for the three and six months ended June 30 , 2019 (dollars in thousands): Three months ended June 30, 2019 Six months ended June 30, 2019 Operating lease cost: Fixed lease cost (Other operating expenses) $ 1,106 $ 2,209 Variable lease cost (Other operating expenses) 244 487 Total operating lease cost $ 1,350 $ 2,696 Finance lease cost: Amortization of ROU asset (Depreciation and amortization) $ 910 $ 1,820 Interest on lease liabilities (Interest expense) 699 1,398 Total finance lease cost $ 1,609 $ 3,218
Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]	Supplemental cash flow information related to leases was as follows for the six months ended June 30 (dollars in thousands): 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflows: Operating lease payments $ 4,197 Interest on finance lease 1,398 Total operating cash outflows $ 5,595 Finance cash outflows: Principal payments on finance lease $ 1,330
Supplemental Balance Sheet Information Leases [Table Text Block]	Supplemental balance sheet information related to leases was as follows for June 30, 2019 (dollars in thousands): June 30, 2019 Operating Leases Operating lease ROU assets (Other property and investments-net and other non-current assets) $ 70,442 Other current liabilities $ 4,123 Other non-current liabilities and deferred credits 68,228 Total operating lease liabilities $ 72,351 Finance Leases Finance lease ROU assets (Other property and investments-net and other non-current assets) (a) $ 52,800 Other current liabilities (b) $ 2,730 Other non-current liabilities and deferred credits (b) 53,150 Total finance lease liabilities $ 55,880 Weighted Average Remaining Lease Term Operating leases 27.01 years Finance leases 8.39 years Weighted Average Discount Rate Operating leases 3.82 % Finance leases 4.88 % (a) At December 31, 2018, the finance lease ROU assets were included in "Net utility property" on the Condensed Consolidated Balance Sheet. Due to the adoption of ASC 842 on January 1, 2019, the Company has reclassified these amounts to "Other property and investments-net and other non-current assets" on the Condensed Consolidated Balance Sheet such that their presentation as of June 30, 2019 is consistent with operating leases. (b) At December 31, 2018, the finance lease liabilities were included in "Current portion of long-term debt" and "Long-term debt and capital leases" on the Condensed Consolidated Balance Sheet. Due to the adoption of ASC 842 on January 1, 2019, the Company has reclassified these amounts to "Other current liabilities" and "Other non-current liabilities and deferred credits" on the Condensed Consolidated Balance Sheet such that their presentation as of June 30, 2019 is consistent with operating leases.
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	Maturities of lease liabilities (including principal and interest) were as follows as of June 30, 2019 (dollars in thousands): Operating Leases Finance Leases Remainder 2019 $ 4,170 $ 2,726 2020 4,364 5,462 2021 4,367 5,457 2022 4,375 5,460 2023 4,391 5,456 Thereafter 95,939 54,574 Total lease payments $ 117,606 $ 79,135 Less: imputed interest (45,255 ) (23,255 ) Total $ 72,351 $ 55,880
Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block]	Future minimum lease payments (including principal and interest) under Topic 840 as of December 31, 2018 (dollars in thousands): Operating Leases Finance Leases 2019 $ 4,995 $ 5,455 2020 4,876 5,462 2021 4,859 5,457 2022 4,782 5,460 2023 4,780 5,456 Thereafter 102,389 54,574 Total lease payments $ 126,681 $ 81,864 Less: imputed interest — (24,654 ) Total $ 126,681 $ 57,210
Finance Lease, Liability, Maturity [Table Text Block]	Maturities of lease liabilities (including principal and interest) were as follows as of June 30, 2019 (dollars in thousands): Operating Leases Finance Leases Remainder 2019 $ 4,170 $ 2,726 2020 4,364 5,462 2021 4,367 5,457 2022 4,375 5,460 2023 4,391 5,456 Thereafter 95,939 54,574 Total lease payments $ 117,606 $ 79,135 Less: imputed interest (45,255 ) (23,255 ) Total $ 72,351 $ 55,880
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	Future minimum lease payments (including principal and interest) under Topic 840 as of December 31, 2018 (dollars in thousands): Operating Leases Finance Leases 2019 $ 4,995 $ 5,455 2020 4,876 5,462 2021 4,859 5,457 2022 4,782 5,460 2023 4,780 5,456 Thereafter 102,389 54,574 Total lease payments $ 126,681 $ 81,864 Less: imputed interest — (24,654 ) Total $ 126,681 $ 57,210

Derivatives And Risk Manageme_2

Derivatives And Risk Management (Tables)	6 Months Ended
	Jun. 30, 2019
Derivative Instruments and Hedges, Assets [Abstract]
Energy Commodity Derivatives	The following table presents the underlying energy commodity derivative volumes as of June 30, 2019 that are expected to be delivered in each respective year (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical (1) MWh Financial (1) MWh Physical (1) mmBTUs Financial (1) mmBTUs Physical (1) Financial (1) Physical (1) Financial (1) Remainder 2019 1 559 5,378 61,385 82 1,330 481 26,150 2020 — — 1,138 60,253 123 1,055 1,430 23,683 2021 — — — 17,640 — 246 1,049 8,575 2022 — — — 1,350 — — — — 2023 — — — — — — — — Thereafter — — — — — — — — The following table presents the underlying energy commodity derivative volumes as of December 31, 2018 that are expected to be delivered in each respective year (in thousands of MWhs and mmBTUs): Purchases Sales Electric Derivatives Gas Derivatives Electric Derivatives Gas Derivatives Year Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) Physical (1) Financial (1) 2019 206 941 10,732 101,293 197 2,790 2,909 54,418 2020 — — 1,138 47,225 123 959 1,430 14,625 2021 — — — 9,670 — — 1,049 4,100 2022 — — — — — — — — 2023 — — — — — — — — Thereafter — — — — — — — —
Foreign Currency Exchange Contracts	The following table summarizes the foreign currency exchange derivatives that Avista Corp. has outstanding as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Number of contracts 27 31 Notional amount (in United States dollars) $ 2,780 $ 4,018 Notional amount (in Canadian dollars) 3,680 5,386
Interest Rate Swap Agreements	The following table summarizes the unsettled interest rate swap derivatives that Avista Corp. has outstanding as of June 30, 2019 and December 31, 2018 (dollars in thousands): Balance Sheet Date Number of Contracts Notional Amount Mandatory Cash Settlement Date June 30, 2019 6 $ 70,000 2019 6 60,000 2020 3 35,000 2021 9 100,000 2022 December 31, 2018 6 $ 70,000 2019 6 60,000 2020 2 25,000 2021 7 80,000 2022
Derivative Instruments Summary	The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of June 30, 2019 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Asset Gross Liability Collateral Netted Net Asset (Liability) on Balance Sheet Foreign currency exchange derivatives Other current assets $ 33 $ — $ — $ 33 Interest rate swap derivatives Other current assets 771 (338 ) — 433 Other current liabilities — (4,771 ) — (4,771 ) Other non-current liabilities and deferred credits 631 (27,309 ) 5,030 (21,648 ) Energy commodity derivatives Other current assets 582 (247 ) — 335 Other current liabilities 26,541 (52,004 ) 20,960 (4,503 ) Other non-current liabilities and deferred credits 3,996 (14,760 ) 5,214 (5,550 ) Total derivative instruments recorded on the balance sheet $ 32,554 $ (99,429 ) $ 31,204 $ (35,671 ) The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2018 (in thousands): Fair Value Derivative and Balance Sheet Location Gross Asset Gross Liability Collateral Net Asset Foreign currency exchange derivatives Other current liabilities $ — $ (45 ) $ — $ (45 ) Interest rate swap derivatives Other current assets 5,283 — — 5,283 Other property and investments-net and other non-current assets 5,283 (440 ) — 4,843 Other non-current liabilities and deferred credits — (7,391 ) 530 (6,861 ) Energy commodity derivatives Other current assets 400 (130 ) — 270 Other current liabilities 31,457 (73,155 ) 37,790 (3,908 ) Other non-current liabilities and deferred credits 4,426 (21,292 ) 13,427 (3,439 ) Total derivative instruments recorded on the balance sheet $ 46,849 $ (102,453 ) $ 51,747 $ (3,857 )
Schedule of Assets Pledged as Collateral and Related Offsets [Table Text Block]	The following table presents Avista Corp.'s collateral outstanding related to its derivative instruments as of June 30, 2019 and December 31, 2018 (in thousands): June 30, December 31, 2019 2018 Energy commodity derivatives Cash collateral posted $ 26,174 $ 78,025 Letters of credit outstanding 14,600 6,500 Balance sheet offsetting (cash collateral against net derivative positions) 26,174 51,217 Interest rate swap derivatives Cash collateral posted 5,030 530 Balance sheet offsetting (cash collateral against net derivative positions) 5,030 530 Certain of Avista Corp.’s derivative instruments contain provisions that require Avista Corp. to maintain an "investment grade" credit rating from the major credit rating agencies. If Avista Corp.’s credit ratings were to fall below "investment grade," it would be in violation of these provisions, and the counterparties to the derivative instruments could request immediate payment or demand immediate and ongoing collateralization on derivative instruments in net liability positions. The following table presents the aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position and the amount of additional collateral Avista Corp. could be required to post as of June 30, 2019 and December 31, 2018 (in thousands): June 30, December 31, 2019 2018 Energy commodity derivatives Liabilities with credit-risk-related contingent features $ 1,564 $ 2,193 Additional collateral to post 1,563 2,193 Interest rate swap derivatives Liabilities with credit-risk-related contingent features 32,418 7,831 Additional collateral to post 25,986 6,579

Pension Plans And Other Postr_2

Pension Plans And Other Postretirement Benefit Plans (Tables)	6 Months Ended
	Jun. 30, 2019
Components of Net Periodic Benefit Cost	Pension Benefits Other Postretirement Benefits 2019 2018 2019 2018 Three months ended June 30: Service cost (a) $ 4,948 $ 5,450 $ 753 $ 804 Interest cost 7,100 6,466 1,164 1,197 Expected return on plan assets (7,953 ) (8,250 ) (611 ) (500 ) Amortization of prior service cost 75 75 (275 ) 209 Net loss recognition 2,426 1,842 1,329 562 Net periodic benefit cost $ 6,596 $ 5,583 $ 2,360 $ 2,272 Six months ended June 30: Service cost (a) $ 9,822 $ 10,900 $ 1,525 $ 1,608 Interest cost 14,238 12,932 2,536 2,394 Expected return on plan assets (15,768 ) (16,500 ) (1,329 ) (1,000 ) Amortization of prior service cost 150 150 (550 ) (606 ) Net loss recognition 4,841 3,930 2,575 2,217 Net periodic benefit cost $ 13,283 $ 11,412 $ 4,757 $ 4,613 (a) Total service costs in the table above are recorded to the same accounts as labor expense. Labor and benefits expense is recorded to various projects based on whether the work is a capital project or an operating expense. Approximately 40 percent of all labor and benefits is capitalized to utility property and 60 percent is expensed to utility other operating expenses.

Income Taxes Income Taxes (Tabl

Income Taxes Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The following table summarizes the significant factors impacting the difference between our effective tax rate and the federal statutory rate for the three and six months ended June 30 (dollars in thousands): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Federal income taxes at statutory rates $ 4,874 21.0 % $ 6,479 21.0 % $ 35,513 21.0 % $ 20,269 21.0 % Increase (decrease) in tax resulting from: Tax effect of regulatory treatment of utility plant differences (2,139 ) (9.2 ) (1,981 ) (6.4 ) (4,219 ) (2.5 ) (2,999 ) (3.1 ) State income tax expense (8 ) — 60 0.2 1,651 1.0 1,024 1.1 Acquisition costs 112 0.5 73 0.2 (1,712 ) (1.0 ) 119 0.1 Non-plant excess deferred turnaround (1) (5,091 ) (21.9 ) (11 ) — (5,601 ) (3.3 ) (11 ) — Tax loss on sale of METALfx (1,259 ) (5.4 ) — — (1,259 ) (0.8 ) — — Valuation allowance 1,245 5.3 — — 1,245 0.7 — — Settlement of equity awards — — — — 612 0.4 (990 ) (1.0 ) Other 525 2.2 589 1.9 2,046 1.2 (1,493 ) (1.6 ) Total income tax expense (benefit) $ (1,741 ) (7.5 )% $ 5,209 16.9 % $ 28,276 16.7 % $ 15,919 16.5 % (1) In March 2019, the IPUC approved an all-party settlement agreement related to electric tax benefits that were set aside for Colstrip in the 2017 general rate case order. In the approved settlement agreement, the parties agreed to utilize approximately $6.4 million ( $5.1 million when tax-effected) of the electric tax benefits to offset costs associated with accelerating the depreciation of Colstrip Units 3 & 4, to reflect a remaining useful life of those units through December 31, 2027. In the second quarter 2019, the Company recorded a one-time charge to depreciation expense with an offsetting amount included in income tax expense.

Committed Lines of Credit (Tabl

Committed Lines of Credit (Tables)	6 Months Ended
	Jun. 30, 2019
Short-term Debt [Abstract]
Schedule of Line of Credit Facilities [Table Text Block]	outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed line of credit were as follows as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Balance outstanding at end of period (1) $ 169,000 $ 190,000 Letters of credit outstanding at end of period $ 18,603 $ 10,503 Average interest rate at end of period 3.26 % 3.18 %

Long- Term Debt to Affiliated_2

Long- Term Debt to Affiliated Trust Long-Term Debt to Affiliated Trust (Tables)	6 Months Ended
	Jun. 30, 2019
Long-Term Debt to Affiliated Trust [Abstract]
Schedule Of Distribution Rates Paid [Table Text Block]	The distribution rates paid were as follows during the six months ended June 30, 2019 and the year ended December 31, 2018 : June 30, December 31, 2019 2018 Low distribution rate 3.40 % 2.36 % High distribution rate 3.50 % 3.61 % Distribution rate at the end of the period 3.40 % 3.61 %

Fair Value (Tables)

Fair Value (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Inputs, Liabilities, Quantitative Information [Table Text Block]	The following table presents the quantitative information which was used to estimate the fair values of the Level 3 assets and liabilities above as of June 30, 2019 (dollars in thousands): Fair Value (Net) at June 30, 2019 Valuation Technique Unobservable Input Range Natural gas exchange agreement $ (2,992 ) Internally derived Forward purchase prices $1.37 - $2.30/mmBTU Forward sales prices $1.45 - $3.62/mmBTU Purchase volumes 118,162 - 310,000 mmBTUs Sales volumes 60,000 - 310,000 mmBTUs
Fair Value of Assets And Liabilities Measured on Recurring Basis	Level 1 Level 2 Level 3 Counterparty Total June 30, 2019 Assets: Energy commodity derivatives $ — $ 31,074 $ — $ (30,739 ) $ 335 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 45 (45 ) — Foreign currency exchange derivatives — 33 — — 33 Interest rate swap derivatives — 1,402 — (969 ) 433 Deferred compensation assets: Mutual Funds: Fixed income securities (2) 1,787 — — — 1,787 Equity securities (2) 6,325 — — — 6,325 Total $ 8,112 $ 32,509 $ 45 $ (31,753 ) $ 8,913 Liabilities: Energy commodity derivatives $ — $ 63,974 $ — $ (56,913 ) $ 7,061 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 3,037 (45 ) 2,992 Interest rate swap derivatives — 32,418 — (5,999 ) 26,419 Total $ — $ 96,392 $ 3,037 $ (62,957 ) $ 36,472 Level 1 Level 2 Level 3 Counterparty Total December 31, 2018 Assets: Energy commodity derivatives $ — $ 36,252 $ — $ (35,982 ) $ 270 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 31 (31 ) — Interest rate swap derivatives — 10,566 — (440 ) 10,126 Deferred compensation assets: Mutual Funds: Fixed income securities (2) 1,745 — — — 1,745 Equity securities (2) 6,157 — — — 6,157 Total $ 7,902 $ 46,818 $ 31 $ (36,453 ) $ 18,298 Liabilities: Energy commodity derivatives $ — $ 89,283 $ — $ (87,199 ) $ 2,084 Level 3 energy commodity derivatives: Natural gas exchange agreement — — 2,805 (31 ) 2,774 Power exchange agreement — — 2,488 — 2,488 Power option agreement — — 1 — 1 Foreign currency exchange derivatives — 45 — — 45 Interest rate swap derivatives — 7,831 — (970 ) 6,861 Total $ — $ 97,159 $ 5,294 $ (88,200 ) $ 14,253 (1) The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties. (2) These assets are included in other property and investments-net and other non-current assets on the Condensed Consolidated Balance Sheets.
Reconciliation for All Assets Measured At Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)	Natural Gas Exchange Agreement Power Exchange Agreement Total Three months ended June 30, 2019: Balance as of April 1, 2019 $ (2,104 ) $ (612 ) $ (2,716 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities (1) (829 ) 1,454 625 Settlements (59 ) (842 ) (901 ) Ending balance as of June 30, 2019 (2) $ (2,992 ) $ — $ (2,992 ) Natural Gas Exchange Agreement Power Exchange Agreement Total Three months ended June 30, 2018: Balance as of April 1, 2018 $ (2,805 ) $ (10,163 ) $ (12,968 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities (1) (768 ) 2,597 1,829 Settlements 93 1,221 1,314 Ending balance as of June 30, 2018 (2) $ (3,480 ) $ (6,345 ) $ (9,825 ) Six months ended June 30, 2019: Balance as of January 1, 2019 $ (2,774 ) $ (2,488 ) $ (5,262 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities (1) 8,148 436 8,584 Settlements (8,366 ) 2,052 (6,314 ) Ending balance as of June 30, 2019 (2) $ (2,992 ) $ — $ (2,992 ) Six months ended June 30, 2018: Balance as of January 1, 2018 $ (3,164 ) $ (13,245 ) $ (16,409 ) Total gains or (losses) (realized/unrealized): Included in regulatory assets/liabilities (1) (565 ) 720 155 Settlements 249 6,180 6,429 Ending balance as of June 30, 2018 (2) $ (3,480 ) $ (6,345 ) $ (9,825 ) (1) All gains and losses are included in other regulatory assets and liabilities. There were no gains and losses included in either net income or other comprehensive income during any of the periods presented in the table above. (2) There were no purchases, issuances or transfers from other categories of any derivatives instruments during the periods presented in the table above.
Carrying Value and Estimated Fair Value of Financial Instruments	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 June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, 2019 December 31, 2018 Carrying Value Estimated Fair Value Carrying Value Estimated Fair Value Long-term debt (Level 2) $ 1,053,500 $ 1,198,009 $ 1,053,500 $ 1,142,292 Long-term debt (Level 3) 767,000 762,204 767,000 734,742 Snettisham finance lease obligation (Level 3) 55,880 58,200 57,210 55,600 Long-term debt to affiliated trusts (Level 3) 51,547 39,691 51,547 38,145

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss (Tables)	6 Months Ended
	Jun. 30, 2019
Accumulated Other Comprehensive Loss [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Accumulated other comprehensive loss, net of tax, consisted of the following as of June 30, 2019 and December 31, 2018 (dollars in thousands): June 30, December 31, 2019 2018 Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $2,006 and $2,091, respectively $ 7,545 $ 7,866
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The following table details the reclassifications out of accumulated other comprehensive loss to net income by component for the three and six months ended June 30 (dollars in thousands). Amounts Reclassified from Accumulated Other Comprehensive Loss Three months ended June 30, Six months ended June 30, Details about Accumulated Other Comprehensive Loss Components 2019 2018 2019 2018 Affected Line Item in Statement of Income Amortization of defined benefit pension items Amortization of net prior service cost $ (200 ) $ (228 ) $ (400 ) $ (456 ) (a) Amortization of net loss 3,755 2,995 7,416 5,990 (a) Adjustment due to effects of regulation (3,352 ) (2,509 ) (6,610 ) (5,017 ) (a) 203 258 406 517 Total before tax (42 ) (54 ) (85 ) (109 ) Tax expense $ 161 $ 204 $ 321 $ 408 Net of tax (a) These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details).

Earnings Per Common Share Att_2

Earnings Per Common Share Attributable To Avista Corporation (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Computations Of Earnings Per Share	The following table presents the computation of basic and diluted earnings per common share attributable to Avista Corp. shareholders for the three and six months ended June 30 (in thousands, except per share amounts): Three months ended June 30, Six months ended June 30, 2019 2018 2019 2018 Numerator: Net income attributable to Avista Corp. shareholders $ 25,319 $ 25,577 $ 141,113 $ 80,467 Denominator: Weighted-average number of common shares outstanding-basic 65,894 65,677 65,814 65,658 Effect of dilutive securities: Performance and restricted stock awards 69 306 69 299 Weighted-average number of common shares outstanding-diluted 65,963 65,983 65,883 65,957 Earnings per common share attributable to Avista Corp. shareholders: Basic $ 0.38 $ 0.39 $ 2.14 $ 1.23 Diluted $ 0.38 $ 0.39 $ 2.14 $ 1.22

Information By Business Segme_2

Information By Business Segments (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Information by Business Segments	The following table presents information for each of the Company’s business segments (dollars in thousands): Avista Utilities Alaska Electric Light and Power Company Total Utility Other Intersegment Eliminations (1) Total For the three months ended June 30, 2019: Operating revenues $ 289,808 $ 8,743 $ 298,551 $ 2,261 $ — $ 300,812 Resource costs 88,506 (67 ) 88,439 — — 88,439 Other operating expenses (2) 84,602 3,129 87,731 6,332 — 94,063 Depreciation and amortization 53,070 2,409 55,479 155 — 55,634 Income (loss) from operations 40,978 3,016 43,994 (4,226 ) — 39,768 Interest expense (3) 24,316 1,595 25,911 148 (197 ) 25,862 Income taxes (2,947 ) 380 (2,567 ) 826 — (1,741 ) Net income attributable to Avista Corp. shareholders 21,219 1,076 22,295 3,024 — 25,319 Capital expenditures (4) 103,297 3,076 106,373 22 — 106,395 For the three months ended June 30, 2018: Operating revenues $ 302,222 $ 10,482 $ 312,704 $ 6,594 $ — $ 319,298 Resource costs 103,022 2,947 105,969 — — 105,969 Other operating expenses (2) (5) 78,848 3,213 82,061 6,543 — 88,604 Depreciation and amortization 44,186 1,465 45,651 199 — 45,850 Income (loss) from operations (5) 50,848 2,579 53,427 (148 ) — 53,279 Interest expense (3) 24,428 896 25,324 382 (234 ) 25,472 Income taxes 4,735 446 5,181 28 — 5,209 Net income attributable to Avista Corp. shareholders 24,252 1,282 25,534 43 — 25,577 Capital expenditures (4) 97,963 3,352 101,315 338 — 101,653 Avista Utilities Alaska Electric Light and Power Company Total Utility Other Intersegment Eliminations (1) Total For the six months ended June 30, 2019: Operating revenues $ 667,510 $ 19,624 $ 687,134 $ 10,159 $ — $ 697,293 Resource costs 227,218 (1,432 ) 225,786 — — 225,786 Other operating expenses (2) 185,185 6,188 191,373 13,687 — 205,060 Depreciation and amortization 99,577 4,816 104,393 364 — 104,757 Income (loss) from operations 101,202 9,529 110,731 (3,892 ) — 106,839 Interest expense (3) 48,580 3,191 51,771 736 (637 ) 51,870 Income taxes 25,597 1,743 27,340 936 — 28,276 Net income attributable to Avista Corp. shareholders 133,120 4,628 137,748 3,365 — 141,113 Capital expenditures (4) 195,606 4,382 199,988 184 — 200,172 For the six months ended June 30, 2018: Operating revenues $ 690,976 $ 24,145 $ 715,121 $ 13,538 $ — $ 728,659 Resource costs 254,687 5,900 260,587 — — 260,587 Other operating expenses (2) 153,987 6,044 160,031 13,367 — 173,398 Depreciation and amortization 87,453 2,931 90,384 380 — 90,764 Income (loss) from operations 138,993 8,701 147,694 (209 ) — 147,485 Interest expense (3) 48,393 1,790 50,183 717 (399 ) 50,501 Income taxes 15,152 1,910 17,062 (1,143 ) — 15,919 Net income (loss) attributable to Avista Corp. shareholders 79,792 5,054 84,846 (4,379 ) — 80,467 Capital expenditures (4) 179,139 3,993 183,132 552 — 183,684 Total Assets: As of June 30, 2019: $ 5,520,529 $ 277,934 $ 5,798,463 $ 107,753 $ (28,288 ) $ 5,877,928 As of December 31, 2018: $ 5,458,104 $ 272,950 $ 5,731,054 $ 87,050 $ (35,528 ) $ 5,782,576 (1) Intersegment eliminations reported as interest expense represent intercompany interest. (2) Other operating expenses for Avista Utilities for the three and six months ended June 30 , 2019 and 2018 include merger transaction costs which are separately disclosed on the Condensed Consolidated Statements of Income. (3) Including interest expense to affiliated trusts. (4) The capital expenditures for the other businesses are included in other investing activities on the Condensed Consolidated Statements of Cash Flows.

New Accounting Standards New Ac

New Accounting Standards New Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Document Period End Date			Jun. 30, 2019
AOCI Attributable to Parent [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of excess income tax benefits	$ 0	$ 0	$ 0	$ (1,742)

Balance Sheet Components Materi

Balance Sheet Components Materials and Supplies, Fuel Stock and Stored Natural Gas (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Inventory, Raw Materials and Supplies, Gross	$ 46,886	$ 47,403
Other Inventory, Gross	6,332	4,869
Energy Related Inventory, Gas Stored Underground	14,441	11,609
Inventory, Net	$ 67,659	$ 63,881

Balance Sheet Components Other

Balance Sheet Components Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$ 0	$ 26,809
Prepayments	24,515	17,536
Other	6,084	9,665
Other Assets, Current	$ 30,599	$ 54,010

Balance Sheet Components Net Ut

Balance Sheet Components Net Utility Property (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Utility plant in service	$ 6,262,789	$ 6,209,968
Construction work in progress	191,845	160,598
Total	6,454,634	6,370,566
Less: Accumulated depreciation and amortization	1,769,980	1,721,636
Total net utility property	$ 4,684,654	$ 4,648,930

Balance Sheet Components Othe_2

Balance Sheet Components Other Property and Investments-Net and Non-current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Operating Lease, Right-of-Use Asset	$ 70,442	$ 0
Finance Lease, Right-of-Use Asset	52,800	0
Non-utility property	28,438	31,355
Equity investments	36,921	29,257
Investment in affiliated trust	11,547	11,547
Notes receivable	11,376	11,073
Deferred compensation assets	8,557	8,400
Other	20,549	23,065
Investments and Other Noncurrent Assets	$ 240,630	$ 114,697

Balance Sheet Components Othe_3

Balance Sheet Components Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Accrued taxes other than income taxes	$ 35,502	$ 36,858
Employee paid time off accruals	22,092	20,992
Accrued interest	16,536	16,704
Current portion of pensions and other postretirement benefits	11,175	9,151
Derivative liabilities	9,274	3,908
Other current liabilities	29,590	32,745
Other current liabilities	$ 124,169	$ 120,358

Balance Sheet Components Othe_4

Balance Sheet Components Other Non-Current Liabilities and Deferred Credits (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Operating Lease, Liability, Noncurrent	$ 68,228	$ 0
Finance Lease, Liability, Noncurrent	53,150	0
Deferred investment tax credits	31,172	29,725
Asset Retirement Obligation	18,595	18,266
Derivative Liability, Noncurrent	27,198	10,300
Other	13,058	12,740
Other Liabilities, Noncurrent	$ 211,401	$ 71,031

Balance Sheet Components Regula

Balance Sheet Components Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Regulated Asset Liability [Line Items]
Regulatory assets	$ 38,785	$ 48,552
Regulatory Assets, Noncurrent	630,451	614,354
Regulatory liabilities	37,954	113,209
Non-current regulatory liabilities	789,655	780,701
Income Tax Related
Regulated Asset Liability [Line Items]
Regulatory liabilities	23,079	27,997
Non-current regulatory liabilities	418,039	425,613
Natural Gas Deferrals [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	1,852	40,713
Non-current regulatory liabilities	0	0
Power Deferrals Regulatory Liability [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	6,612	25,072
Non-current regulatory liabilities	32,617	16,933
Decoupling surcharge
Regulated Asset Liability [Line Items]
Regulatory liabilities	437	6,782
Non-current regulatory liabilities	2,861	204
Removal Costs [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	0	0
Non-current regulatory liabilities	302,734	297,379
Interest rate swaps
Regulated Asset Liability [Line Items]
Regulatory liabilities	0	0
Non-current regulatory liabilities	17,659	28,078
Other Regulatory Assets (Liabilities) [Member]
Regulated Asset Liability [Line Items]
Regulatory liabilities	5,974	12,645
Non-current regulatory liabilities	15,745	12,494
Energy commodity derivatives
Regulated Asset Liability [Line Items]
Regulatory assets	25,125	41,428
Regulatory Assets, Noncurrent	10,764	16,866
Decoupling surcharge
Regulated Asset Liability [Line Items]
Regulatory assets	6,498	3,408
Regulatory Assets, Noncurrent	16,167	17,501
Pension and other postretirement benefit plans
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	221,454	228,062
Interest rate swaps
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	155,787	133,854
Income Tax Related
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	95,217	91,188
Settlement with Coeur d'Alene Tribe
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	41,988	42,643
Demand side management programs
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	13,705	19,674
Utility plant to be abandoned
Regulated Asset Liability [Line Items]
Regulatory assets	0	0
Regulatory Assets, Noncurrent	25,273	24,334
Other Regulatory Assets (Liabilities) [Member]
Regulated Asset Liability [Line Items]
Regulatory assets	7,162	3,716
Regulatory Assets, Noncurrent	$ 50,096	$ 40,232

Revenue Revenue Utility Related

Revenue Revenue Utility Related Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Public Utility Operating Expenses Excise Taxes Collected	$ 12,688	$ 12,986	$ 31,777	$ 32,153

Revenue Revenue Unsatisfied Per

Revenue Revenue Unsatisfied Performance Obligations (Details) $ in Millions	Jun. 30, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 7.9

Revenue Revenue Disaggregation

Revenue Revenue Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 300,812	$ 319,298	$ 697,293	$ 728,659
Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	76,610	78,973	197,855	200,264
Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	81,212	83,003	165,279	169,956
Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26,245	27,985	51,493	53,104
Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,956	1,962	3,922	3,889
Total Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	186,023	191,923	418,549	427,213
Electric Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,250	4,171	9,402	8,001
Other Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,379	3,919	12,573	10,210
Total Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	194,652	200,013	440,524	445,424
Residential Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	27,937	30,767	105,272	111,421
Commercial Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	13,369	14,668	49,964	52,040
Industrial and Interruptible Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,103	1,078	2,730	2,761
Total Retail Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	42,409	46,513	157,966	166,222
Transportation Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,039	2,221	4,523	4,788
Other Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,125	1,125	2,250	2,250
Total Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	45,573	49,859	164,739	173,260
Avista Utilities [Member]
Disaggregation of Revenue [Line Items]
Revenues	289,808	302,222	667,510	690,976
Avista Utilities [Member] | Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	72,886	74,818	188,279	189,571
Avista Utilities [Member] | Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	76,375	76,462	155,621	155,371
Avista Utilities [Member] | Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26,245	27,985	51,493	53,104
Avista Utilities [Member] | Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,897	1,899	3,800	3,758
Avista Utilities [Member] | Total Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	177,403	181,164	399,193	401,804
Avista Utilities [Member] | Electric Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,250	4,171	9,402	8,001
Avista Utilities [Member] | Other Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,379	3,919	12,573	10,210
Avista Utilities [Member] | Total Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	186,032	189,254	421,168	420,015
Avista Utilities [Member] | Residential Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	27,937	30,767	105,272	111,421
Avista Utilities [Member] | Commercial Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	13,369	14,668	49,964	52,040
Avista Utilities [Member] | Industrial and Interruptible Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,103	1,078	2,730	2,761
Avista Utilities [Member] | Total Retail Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	42,409	46,513	157,966	166,222
Avista Utilities [Member] | Transportation Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,039	2,221	4,523	4,788
Avista Utilities [Member] | Other Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,125	1,125	2,250	2,250
Avista Utilities [Member] | Total Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	45,573	49,859	164,739	173,260
Avista Utilities [Member] | Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	231,605	239,113	585,907	593,275
Avista Utilities [Member] | Derivative revenues
Disaggregation of Revenue [Line Items]
Revenues	42,128	56,357	66,255	114,749
Avista Utilities [Member] | Alternative Revenue Programs [Member]
Disaggregation of Revenue [Line Items]
Revenues	9,725	3,570	5,067	(2,369)
Avista Utilities [Member] | Deferrals and amortizations for rate refunds to customers
Disaggregation of Revenue [Line Items]
Revenues	2,512	982	4,647	(18,840)
Avista Utilities [Member] | Other utility revenues
Disaggregation of Revenue [Line Items]
Revenues	3,838	2,200	5,634	4,161
Alaska Electric Light & Power [Member]
Disaggregation of Revenue [Line Items]
Revenues	8,743	10,482	19,624	24,145
Alaska Electric Light & Power [Member] | Residential Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,724	4,155	9,576	10,693
Alaska Electric Light & Power [Member] | Commercial and Governmental Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,837	6,541	9,658	14,585
Alaska Electric Light & Power [Member] | Industrial Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Public Street and Highway Lighting Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	59	63	122	131
Alaska Electric Light & Power [Member] | Total Retail Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	8,620	10,759	19,356	25,409
Alaska Electric Light & Power [Member] | Electric Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Other Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Total Electric [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	8,620	10,759	19,356	25,409
Alaska Electric Light & Power [Member] | Residential Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Commercial Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Industrial and Interruptible Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Total Retail Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Transportation Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Other Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Total Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Alaska Electric Light & Power [Member] | Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	8,620	10,759	19,356	25,409
Alaska Electric Light & Power [Member] | Deferrals and amortizations for rate refunds to customers
Disaggregation of Revenue [Line Items]
Revenues	(47)	(427)	(95)	(1,549)
Alaska Electric Light & Power [Member] | Other utility revenues
Disaggregation of Revenue [Line Items]
Revenues	170	150	363	285
Corporate and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,261	6,594	10,159	13,538
Corporate and Other [Member] | Revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Revenues	2,024	6,324	9,671	13,053
Corporate and Other [Member] | Other revenues
Disaggregation of Revenue [Line Items]
Revenues	$ 237	$ 270	$ 488	$ 485

Leases Leases (Details)

Leases Leases (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Lessee, Lease, Description [Line Items]
Lessor, Operating Lease, Not Yet Commenced, Assumption and Judgment, Estimated Annual Operating Expense	$ 1.1
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:InvestmentsAndOtherNoncurrentAssets
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:InvestmentsAndOtherNoncurrentAssets
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	1 year
Lessee, Operating Lease, Renewal Term	5 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	74 years
Lessee, Operating Lease, Renewal Term	50 years
State of Montana [Member]
Lessee, Lease, Description [Line Items]
Lease Expiration Date	Dec. 31, 2046
Snettisham Hydroelectric Project [Member]
Lessee, Lease, Description [Line Items]
Lease Expiration Date	Dec. 31, 2034

Leases Leases Components of Lea

Leases Leases Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	$ 1,106	$ 2,209
Variable Lease, Cost	244	487
Finance Lease, Right-of-Use Asset, Amortization	910	1,820
Finance Lease, Interest Expense	699	1,398
Operating Lease [Member]
Lessee, Lease, Description [Line Items]
Lease, Cost	1,350	2,696
Finance Lease [Member]
Lessee, Lease, Description [Line Items]
Lease, Cost	$ 1,609	$ 3,218

Leases Leases Supplemental Cash

Leases Leases Supplemental Cash Flow Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Leases [Abstract]
Operating Lease, Payments	$ 4,197
Finance Lease, Interest Payment on Liability	1,398
Total Lease Payments in Operating Cash Flows	5,595
Finance Lease, Principal Payments	$ 1,330

Leases Leases Supplemental Bala

Leases Leases Supplemental Balance Sheet Disclosures (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Finance Lease, Liability	$ 55,880
Operating Lease, Liability	72,351
Operating Lease, Right-of-Use Asset	70,442	$ 0
Operating Lease, Liability, Current	4,123
Operating Lease, Liability, Noncurrent	68,228	0
Finance Lease, Right-of-Use Asset	52,800	0
Finance Lease, Liability, Current	2,730
Finance Lease, Liability, Noncurrent	$ 53,150	$ 0
Operating Lease, Weighted Average Remaining Lease Term	27 years 3 days
Finance Lease, Weighted Average Remaining Lease Term	8 years 4 months 20 days
Operating Lease, Weighted Average Discount Rate, Percent	3.82%
Finance Lease, Weighted Average Discount Rate, Percent	4.88%

Leases Leases Maturities of Lea

Leases Leases Maturities of Lease Liabilities (Details) $ in Thousands	Jun. 30, 2019USD ($)
Leases [Abstract]
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 4,170
Lessee, Operating Lease, Liability, Payments, Due Year Two	4,364
Lessee, Operating Lease, Liability, Payments, Due Year Three	4,367
Lessee, Operating Lease, Liability, Payments, Due Year Four	4,375
Lessee, Operating Lease, Liability, Payments, Due Year Five	4,391
Lessee, Operating Lease, Liability, Payments, Due after Year Five	95,939
Lessee, Operating Lease, Liability, Payments, Due	117,606
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(45,255)
Operating Lease, Liability	72,351
Finance Lease, Liability, Payments, Remainder of Fiscal Year	2,726
Finance Lease, Liability, Payments, Due Year Two	5,462
Finance Lease, Liability, Payments, Due Year Three	5,457
Finance Lease, Liability, Payments, Due Year Four	5,460
Finance Lease, Liability, Payments, Due Year Five	5,456
Finance Lease, Liability, Payments, Due after Year Five	54,574
Finance Lease, Liability, Payments, Due	79,135
Finance Lease, Liability, Undiscounted Excess Amount	(23,255)
Finance Lease, Liability	$ 55,880

Leases Leases Future Minimum Le

Leases Leases Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 4,995
Operating Leases, Future Minimum Payments, Due in Two Years	4,876
Operating Leases, Future Minimum Payments, Due in Three Years	4,859
Operating Leases, Future Minimum Payments, Due in Four Years	4,782
Operating Leases, Future Minimum Payments, Due in Five Years	4,780
Operating Leases, Future Minimum Payments, Due Thereafter	102,389
Operating Leases Future Minimum Payments Interest Included In Payments	0
Operating Leases, Future Minimum Payments Due	126,681
Capital Leases, Future Minimum Payments Due, Next Twelve Months	5,455
Capital Leases, Future Minimum Payments Due in Two Years	5,462
Capital Leases, Future Minimum Payments Due in Three Years	5,457
Capital Leases, Future Minimum Payments Due in Four Years	5,460
Capital Leases, Future Minimum Payments Due in Five Years	5,456
Capital Leases, Future Minimum Payments Due Thereafter	54,574
Capital Leases, Future Minimum Payments Due	81,864
Capital Leases, Future Minimum Payments, Interest Included in Payments	(24,654)
Capital Lease Obligations	$ 57,210

Derivatives And Risk Manageme_3

Derivatives And Risk Management (Narrative) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net	$ 31,204	$ 51,747
Commodity Contracts [Member]
Derivative [Line Items]
Cash deposited as collateral	26,174	78,025
Letters of credit outstanding	14,600	6,500
Derivative, Fair Value, Amount Offset Against Collateral, Net	26,174	51,217
Liability position at aggregate fair value	1,564	2,193
Additional Collateral, Aggregate Fair Value	1,563	2,193
Interest Rate Swap [Member]
Derivative [Line Items]
Cash deposited as collateral	5,030	530
Derivative, Fair Value, Amount Offset Against Collateral, Net	5,030	530
Liability position at aggregate fair value	32,418	7,831
Additional Collateral, Aggregate Fair Value	$ 25,986	$ 6,579

Derivatives And Risk Manageme_4

Derivatives And Risk Management (Energy Commodity Derivatives) (Details) frequency in Thousands, Volt in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019Voltfrequency	Dec. 31, 2018Voltfrequency
Sales [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2019	82	197
2020	123	123
2021	0	0
2022	0	0
2023	0	0
Thereafter	0	0
Sales [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2019 | Volt	481	2,909
2020 | Volt	1,430	1,430
2021 | Volt	1,049	1,049
2022	0	0
2023	0	0
Thereafter | Volt	0	0
Sales [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2019	1,330	2,790
2020	1,055	959
2021	246	0
2022	0	0
2023	0	0
Thereafter	0	0
Sales [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2019 | Volt	26,150	54,418
2020 | Volt	23,683	14,625
2021 | Volt	8,575	4,100
2022 | Volt	0	0
2023	0	0
Thereafter | Volt	0	0
Purchase [Member] | Physical [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2019	1	206
2020	0	0
2021	0	0
2022	0	0
2023	0	0
Thereafter	0	0
Purchase [Member] | Physical [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2019 | Volt	5,378	10,732
2020 | Volt	1,138	1,138
2021 | Volt	0	0
2022 | Volt	0	0
2023 | Volt	0	0
Thereafter | Volt	0	0
Purchase [Member] | Financial [Member] | Electric Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2019	559	941
2020	0	0
2021	0	0
2022	0	0
2023	0	0
Thereafter	0	0
Purchase [Member] | Financial [Member] | Gas Derivative [Member]
Energy Commodity Derivative Volumes [Line Items]
2019 | Volt	61,385	101,293
2020 | Volt	60,253	47,225
2021 | Volt	17,640	9,670
2022 | Volt	1,350	0
2023 | Volt	0	0
Thereafter | Volt	0	0

Derivatives And Risk Manageme_5

Derivatives And Risk Management Derivatives and Risk Management (Foreign Currency Exchange Contracts) (Details) $ in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)derivative_contracts	Jun. 30, 2019CAD ($)derivative_contracts	Dec. 31, 2018USD ($)derivative_contracts	Dec. 31, 2018CAD ($)derivative_contracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Number Of Days Canadian Currency Prices Are Settled With U.S. Dollars	60 days
Number of Foreign Currency Derivatives Held | derivative_contracts	27	27	31	31
United States of America, Dollars | Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Derivative, Notional Amount	$ 2,780		$ 4,018
Canada, Dollars | Foreign Exchange Contract [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Derivative, Notional Amount		$ 3,680		$ 5,386

Derivatives And Risk Manageme_6

Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) - Interest Rate Swap [Member] $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019USD ($)Caontracts	Dec. 31, 2018USD ($)Caontracts
2019
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held | Caontracts	6	6
Derivative, Notional Amount | $	$ 70,000	$ 70,000
Mandatory Cash Settlement Date	2019	2019
2020
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held | Caontracts	6	6
Derivative, Notional Amount | $	$ 60,000	$ 60,000
Mandatory Cash Settlement Date	2020	2020
2021
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held | Caontracts	3	2
Derivative, Notional Amount | $	$ 35,000	$ 25,000
Mandatory Cash Settlement Date	2021	2021
2022
Derivatives, Fair Value [Line Items]
Number of Interest Rate Derivatives Held | Caontracts	9	7
Derivative, Notional Amount | $	$ 100,000	$ 80,000
Mandatory Cash Settlement Date	2022	2022

Derivatives And Risk Manageme_7

Derivatives And Risk Management (Derivative Instruments Summary) (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Gross Asset	$ 32,554,000	$ 46,849,000
Gross Liability	(99,429,000)	(102,453,000)
Collateral Netted	31,204,000	51,747,000
Net Asset (Liability) on Balance Sheet	(35,671,000)	(3,857,000)
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	5,030,000	530,000
Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Collateral Netted	26,174,000	51,217,000
Other Current Liabilities [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		0
Gross Liability		(45,000)
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		(45,000)
Other Current Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	0
Gross Liability	(4,771,000)
Collateral Netted	0
Net Asset (Liability) on Balance Sheet	(4,771,000)
Other Current Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	26,541,000	31,457,000
Gross Liability	(52,004,000)	(73,155,000)
Collateral Netted	20,960,000	37,790,000
Net Asset (Liability) on Balance Sheet	(4,503,000)	(3,908,000)
Other Current Assets [Member] | Foreign Exchange Contract [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	33,000
Gross Liability	0
Collateral Netted	0
Net Asset (Liability) on Balance Sheet	33,000
Other Current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	771,000	5,283,000
Gross Liability	(338,000)	0
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	433,000	5,283,000
Other Current Assets [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	582,000	400,000
Gross Liability	(247,000)	(130,000)
Collateral Netted	0	0
Net Asset (Liability) on Balance Sheet	335,000	270,000
Other Property And Investments Net And Other Non-current Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset		5,283,000
Gross Liability		(440,000)
Collateral Netted		0
Net Asset (Liability) on Balance Sheet		4,843,000
Other Noncurrent Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	631,000	0
Gross Liability	(27,309,000)	(7,391,000)
Collateral Netted	5,030,000	530,000
Net Asset (Liability) on Balance Sheet	(21,648,000)	(6,861,000)
Other Noncurrent Liabilities [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Asset	3,996,000	4,426,000
Gross Liability	(14,760,000)	(21,292,000)
Collateral Netted	5,214,000	13,427,000
Net Asset (Liability) on Balance Sheet	$ (5,550,000)	$ (3,439,000)

Derivatives And Risk Manageme_8

Derivatives And Risk Management Derivatives and Risk Management (Collateral) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net	$ 31,204	$ 51,747
Commodity Contracts [Member]
Derivative [Line Items]
Liability position at aggregate fair value	1,564	2,193
Additional Collateral, Aggregate Fair Value	1,563	2,193
Collateral Already Posted, Aggregate Fair Value	26,174	78,025
Letters of credit outstanding	14,600	6,500
Derivative, Fair Value, Amount Offset Against Collateral, Net	26,174	51,217
Foreign Exchange Contract [Member]
Derivative [Line Items]
Collateral Already Posted, Aggregate Fair Value	0	0
Letters of credit outstanding	$ 0	$ 0

Pension Plans And Other Postr_3

Pension Plans And Other Postretirement Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits	$ 14,600	$ 14,600
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year	$ 22,000

Pension Plans And Other Postr_4

Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Percentage of Net Periodic Benefit Costs Capitalized to Utility Property			40.00%
Percentage of Net Periodic Benefit Costs Recorded to Operating Expenses			60.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 4,948	$ 5,450	$ 9,822	$ 10,900
Interest cost	7,100	6,466	14,238	12,932
Expected return on plan assets	(7,953)	(8,250)	(15,768)	(16,500)
Amortization of prior service cost	75	75	150	150
Net loss recognition	2,426	1,842	4,841	3,930
Net periodic benefit cost	6,596	5,583	13,283	11,412
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	753	804	1,525	1,608
Interest cost	1,164	1,197	2,536	2,394
Expected return on plan assets	(611)	(500)	(1,329)	(1,000)
Amortization of prior service cost	(275)	209	(550)	(606)
Net loss recognition	1,329	562	2,575	2,217
Net periodic benefit cost	$ 2,360	$ 2,272	$ 4,757	$ 4,613

Income Taxes Income Taxes (Deta

Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Effective Tax Rate Reconciliation [Line Items]
Regulatory liabilities	$ 37,954		$ 37,954		$ 113,209
Federal income taxes at statutory rates	$ 4,874	$ 6,479	$ 35,513	$ 20,269
Federal income taxes at statutory rates	21.00%	21.00%	21.00%	21.00%
Tax effect of regulatory treatment of utility plant differences	$ (2,139)	$ (1,981)	$ (4,219)	$ (2,999)
Tax effect of regulatory treatment of utility plant differences	(9.20%)	(6.40%)	(2.50%)	(3.10%)
State income tax expense	$ (8)	$ 60	$ 1,651	$ 1,024
State income tax expense	0.00%	0.20%	1.00%	1.10%
Acquisition costs	$ 112	$ 73	$ (1,712)	$ 119
Acquisition costs	0.50%	0.20%	(1.00%)	0.10%
Non-plant excess deferred turnaround (1)	$ (5,091)	$ (11)	$ (5,601)	$ (11)
Non-plant excess deferred turnaround (1)	(21.90%)	0.00%	(3.30%)	0.00%
Tax loss on sale of METALfx	$ (1,259)	$ 0	$ (1,259)	$ 0
Tax loss on sale of METALfx	(5.40%)	0.00%	(0.80%)	0.00%
Valuation allowance	$ 1,245	$ 0	$ 1,245	$ 0
Valuation allowance	5.30%	0.00%	0.70%	0.00%
Settlement of equity awards	$ 0	$ 0	$ 612	$ (990)
Settlement of equity awards	0.00%	0.00%	0.40%	(1.00%)
Other	$ 525	$ 589	$ 2,046	$ (1,493)
Other	2.20%	1.90%	1.20%	(1.60%)
Income Tax Expense (Benefit)	$ (1,741)	$ 5,209	$ 28,276	$ 15,919
Effective Income Tax Rate	(7.50%)	16.90%	16.70%	16.50%
Income Tax Related
Effective Tax Rate Reconciliation [Line Items]
Regulatory liabilities	$ 23,079		$ 23,079		$ 27,997
Income Tax Related | IDAHO
Effective Tax Rate Reconciliation [Line Items]
Regulatory liabilities	$ 6,400		$ 6,400

Committed Lines of Credit (Deta

Committed Lines of Credit (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Jul. 01, 2014	Apr. 30, 2014
Short-term Debt [Line Items]
Document Period End Date	Jun. 30, 2019
Avista Utilities [Member]
Short-term Debt [Line Items]
Line of Credit, Current	$ 169,000	$ 190,000
Line of Credit Facility, Maximum Borrowing Capacity				$ 400,000
Letters of credit outstanding at end of period	$ 18,603	$ 10,503
Average interest rate at end of period	3.26%	3.18%
Alaska Electric Light & Power [Member]
Short-term Debt [Line Items]
Line of Credit, Current	$ 0	$ 0
Line of Credit Facility, Maximum Borrowing Capacity			$ 25,000
Letters of credit outstanding at end of period	$ 0	$ 0

Long- Term Debt to Affiliated_3

Long- Term Debt to Affiliated Trust Long-Term Debt to Affiliated Trust (Schedule of Distribution Rates Paid) (Details) - Trust Preferred Securities Subject to Mandatory Redemption [Member]	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest Rate at End of Period	3.40%	3.61%
Minimum [Member]
Debt Instrument [Line Items]
Interest Rate at End of Period	3.40%	2.36%
Maximum [Member]
Debt Instrument [Line Items]
Interest Rate at End of Period	3.50%	3.61%

Long- Term Debt to Affiliated_4

Long- Term Debt to Affiliated Trust Long-Term Debt to Affiliated Trust (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2000	Dec. 31, 1997
Debt Instrument [Line Items]
Proceeds From The Issuance of Common Trust Securities			$ 1.5
Payments for Repurchase of Trust Preferred Securities		$ 10
Equity Method Investment, Ownership Percentage	100.00%
Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust	$ 51.5		51.5
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis	LIBOR
Debt Instrument, Basis Spread on Variable Rate	0.875%
Proceeds from (Repurchase of) Trust Preferred Securities			$ 50

Fair Value (Carrying Value And

Fair Value (Carrying Value And Estimated Fair Value Of Financial Instruments) (Details) $ in Thousands	Jun. 30, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Capital Lease Obligations		$ 57,210
Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 1,198,009	1,142,292
Level 2 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,053,500	1,053,500
Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	762,204	734,742
Level 3 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	767,000	767,000
Alaska Electric Light & Power [Member] | Capital Lease Obligations [Member] | Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Capital Lease Obligations	58,200	55,600
Alaska Electric Light & Power [Member] | Capital Lease Obligations [Member] | Level 3 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Capital Lease Obligations	55,880	57,210
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	39,691	38,145
Affiliated Entity [Member] | Level 3 [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 51,547	$ 51,547
Measurement Input, Quoted Price [Member] | Secured and Unsecured Debt [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Measurement Input | $ / shares	100
Measurement Input, Quoted Price [Member] | Minimum [Member] | Secured and Unsecured Debt [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Measurement Input | $ / shares	77
Measurement Input, Quoted Price [Member] | Maximum [Member] | Secured and Unsecured Debt [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Measurement Input | $ / shares	130.25

Fair Value (Fair Value Of Asset

Fair Value (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	$ 32,554	$ 46,849
Liability	99,429	102,453
Cash and cash equivalents	17,231	14,656	$ 35,333	$ 16,172
Fixed Income Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	400	500
Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	(31,753)	(36,453)
Assets, Fair Value Disclosure	8,913	18,298
Counterparty and collateral netting, liabilities	(62,957)	(88,200)
Financial Liabilities Fair Value Disclosure	36,472	14,253
Fair Value, Measurements, Recurring [Member] | Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	(45)	(31)
Derivative Asset	0	0
Counterparty and collateral netting, liabilities	(45)	(31)
Derivative Liability	2,992	2,774
Fair Value, Measurements, Recurring [Member] | Power Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, liabilities		0
Derivative Liability		2,488
Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	(969)	(440)
Derivative Asset	433	10,126
Counterparty and collateral netting, liabilities	(5,999)	(970)
Derivative Liability	26,419	6,861
Fair Value, Measurements, Recurring [Member] | Energy commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	(30,739)	(35,982)
Derivative Asset	335	270
Counterparty and collateral netting, liabilities	(56,913)	(87,199)
Derivative Liability	7,061	2,084
Fair Value, Measurements, Recurring [Member] | Power Option Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, liabilities		0
Derivative Liability		1
Fair Value, Measurements, Recurring [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Counterparty and collateral netting, assets	0
Derivative Asset	33
Counterparty and collateral netting, liabilities		0
Derivative Liability		45
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	8,112	7,902
Financial Liabilities Fair Value Disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	32,509	46,818
Financial Liabilities Fair Value Disclosure	96,392	97,159
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest Rate Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	1,402	10,566
Liability	32,418	7,831
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Energy commodity derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	31,074	36,252
Liability	63,974	89,283
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign Exchange Contract [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	33
Liability		45
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, Fair Value Disclosure	45	31
Financial Liabilities Fair Value Disclosure	3,037	5,294
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Natural Gas Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross Asset	45	31
Liability	3,037	2,805
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Exchange Agreements [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability		2,488
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Option Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liability		1
Fixed Income Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	1,787	1,745
Fixed Income Funds [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	1,787	1,745
Equity Funds [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	6,325	6,157
Equity Funds [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets:	$ 6,325	$ 6,157

Fair Value (Quantitative Inform

Fair Value (Quantitative Information) (Details) - Natural Gas Exchange Agreements [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)MMBTU$ / MmBtu	Dec. 31, 2018USD ($)
Fair Value, Measurements, Recurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative Liability | $	$ (2,992)	$ (2,774)
Sales [Member] | Minimum [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price | $ / MmBtu	1.45
Transaction/Delivery Volumes | MMBTU	60,000
Sales [Member] | Maximum [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price | $ / MmBtu	3.62
Transaction/Delivery Volumes | MMBTU	310,000
Purchase [Member] | Minimum [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price | $ / MmBtu	1.37
Transaction/Delivery Volumes | MMBTU	118,162
Purchase [Member] | Maximum [Member] | Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Derivative, Forward Price | $ / MmBtu	2.30
Transaction/Delivery Volumes | MMBTU	310,000

Fair Value (Reconciliation For

Fair Value (Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) - Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ (2,716)	$ (12,968)	$ (5,262)	$ (16,409)
Included in regulatory assets/liabilities	625	1,829	8,584	155
Settlements	(901)	1,314	(6,314)	6,429
Ending Balance	(2,992)	(9,825)	(2,992)	(9,825)
Natural Gas Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(2,104)	(2,805)	(2,774)	(3,164)
Included in regulatory assets/liabilities	(829)	(768)	8,148	(565)
Settlements	(59)	93	(8,366)	249
Ending Balance	(2,992)	(3,480)	(2,992)	(3,480)
Power Exchange Agreements [Member]
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(612)	(10,163)	(2,488)	(13,245)
Included in regulatory assets/liabilities	1,454	2,597	436	720
Settlements	(842)	1,221	2,052	6,180
Ending Balance	$ 0	$ (6,345)	$ 0	$ (6,345)

Common Stock Common Stock (Deta

Common Stock Common Stock (Details) - shares	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Sales Agency Agreements Common Stock, Shares Authorized	200,000,000	200,000,000
Document Period End Date	Jun. 30, 2019
Sales Agency Agreement [Member]
Class of Stock [Line Items]
Shares issued from sales agency agreements	400,000
Sales Agency Agreements Common Stock, Shares Authorized	4,600,000
Common Stock Shares Authorized Under Sales Agency Agreements Remaining Shares Authorized To Sell	4,200,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss Reclassifications from AOCL (Details) - Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of net prior service cost	$ (200)	$ (228)	$ (400)	$ (456)
Amortization of net loss	3,755	2,995	7,416	5,990
Adjustment due to effects of regulation	(3,352)	(2,509)	(6,610)	(5,017)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax	203	258	406	517
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	(42)	(54)	(85)	(109)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	$ 161	$ 204	$ 321	$ 408

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Loss [Abstract]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans Net Unamortized (Gain) Loss, Tax	$ 2,006	$ 2,091
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	$ 7,545	$ 7,866

Earnings Per Share Attributable

Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income from continuing operations attributable to Avista Corp. shareholders	$ 25,319	$ 25,577	$ 141,113	$ 80,467
Denominator:
Weighted-average number of common shares outstanding-basic	65,894	65,677	65,814	65,658
Performance and restricted stock awards	69	306	69	299
Weighted-average number of common shares outstanding-diluted	65,963	65,983	65,883	65,957
Earnings Per Share, Basic [Abstract]
Basic	$ 0.38	$ 0.39	$ 2.14	$ 1.23
Earnings Per Share, Diluted [Abstract]
Diluted	$ 0.38	$ 0.39	$ 2.14	$ 1.22

Commitments And Contingencies (

Commitments And Contingencies (Details) $ in Millions	1 Months Ended
	Feb. 28, 2016USD ($)
WASHINGTON | Electricity [Member]
Loss Contingencies [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 8.1

Information By Business Segme_3

Information By Business Segments (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)Reportable_Segments	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments | Reportable_Segments			2
Operating revenues	$ 300,812	$ 319,298	$ 697,293	$ 728,659
Resource costs	88,439	105,969	225,786	260,587
Other operating expenses	94,063	88,604	205,060	173,398
Depreciation and amortization	55,634	45,850	104,757	90,764
Income from operations	39,768	53,279	106,839	147,485
Interest expense	25,862	25,472	51,870	50,501
Income taxes	(1,741)	5,209	28,276	15,919
Net income from continuing operations attributable to Avista Corp. shareholders	25,319	25,577	141,113	80,467
Payments to Acquire Other Property, Plant, and Equipment	106,395	101,653	200,172	183,684
Total assets	5,877,928		5,877,928		$ 5,782,576
Avista Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	289,808	302,222	667,510	690,976
Alaska Electric Light & Power [Member]
Segment Reporting Information [Line Items]
Operating revenues	8,743	10,482	19,624	24,145
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,261	6,594	10,159	13,538
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 from operations	0	0	0	0
Interest expense	(197)	(234)	(637)	(399)
Income taxes	0	0	0	0
Net income from continuing operations attributable to Avista Corp. shareholders	0	0	0	0
Payments to Acquire Other Property, Plant, and Equipment	0	0	0	0
Total assets	(28,288)		(28,288)		(35,528)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues	298,551	312,704	687,134	715,121
Resource costs	88,439	105,969	225,786	260,587
Other operating expenses	87,731	82,061	191,373	160,031
Depreciation and amortization	55,479	45,651	104,393	90,384
Income from operations	43,994	53,427	110,731	147,694
Interest expense	25,911	25,324	51,771	50,183
Income taxes	(2,567)	5,181	27,340	17,062
Net income from continuing operations attributable to Avista Corp. shareholders	22,295	25,534	137,748	84,846
Payments to Acquire Other Property, Plant, and Equipment	106,373	101,315	199,988	183,132
Total assets	5,798,463		5,798,463		5,731,054
Operating Segments [Member] | Avista Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	289,808	302,222	667,510	690,976
Resource costs	88,506	103,022	227,218	254,687
Other operating expenses	84,602	78,848	185,185	153,987
Depreciation and amortization	53,070	44,186	99,577	87,453
Income from operations	40,978	50,848	101,202	138,993
Interest expense	24,316	24,428	48,580	48,393
Income taxes	(2,947)	4,735	25,597	15,152
Net income from continuing operations attributable to Avista Corp. shareholders	21,219	24,252	133,120	79,792
Payments to Acquire Other Property, Plant, and Equipment	103,297	97,963	195,606	179,139
Total assets	5,520,529		5,520,529		5,458,104
Operating Segments [Member] | Alaska Electric Light & Power [Member]
Segment Reporting Information [Line Items]
Operating revenues	8,743	10,482	19,624	24,145
Resource costs	(67)	2,947	(1,432)	5,900
Other operating expenses	3,129	3,213	6,188	6,044
Depreciation and amortization	2,409	1,465	4,816	2,931
Income from operations	3,016	2,579	9,529	8,701
Interest expense	1,595	896	3,191	1,790
Income taxes	380	446	1,743	1,910
Net income from continuing operations attributable to Avista Corp. shareholders	1,076	1,282	4,628	5,054
Payments to Acquire Other Property, Plant, and Equipment	3,076	3,352	4,382	3,993
Total assets	277,934		277,934		272,950
Operating Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,261	6,594	10,159	13,538
Resource costs	0	0	0	0
Other operating expenses	6,332	6,543	13,687	13,367
Depreciation and amortization	155	199	364	380
Income from operations	(4,226)	(148)	(3,892)	(209)
Interest expense	148	382	736	717
Income taxes	826	28	936	(1,143)
Net income from continuing operations attributable to Avista Corp. shareholders	3,024	43	3,365	(4,379)
Payments to Acquire Other Property, Plant, and Equipment	22	$ 338	184	$ 552
Total assets	$ 107,753		$ 107,753		$ 87,050

Termination of Proposed Acqui_2

Termination of Proposed Acquisition by Hydro One Termination of Proposed Acquisition by Hydro One (Details) - USD ($) $ in Thousands	Jan. 24, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Merger termination fee		$ 0	$ 0	$ 103,000
Merger transaction costs		$ 11	$ 983	$ 19,675	$ 1,655
Hydro One [Member]
Business Acquisition [Line Items]
Merger termination fee	$ 103,000

Sale of METALfx Sale of METAL_2

Sale of METALfx Sale of METALfx (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Apr. 18, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent		89.20%
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group Including Discontinued Operation Gross Consideration		$ 17.5
Disposal Group Including Discontinued Operation Consideration Held in Escrow		$ 1.2
Disposal Group Including Discontinued Operation Percentage of Gross Consideration Held in Escrow		7.00%
Disposal Group, Including Discontinued Operation, Consideration		$ 16.5
Disposal Group Not Discontinued Operation Gain (Loss) On Disposal Net of Tax	$ 2.3