Avista (AVA) 10-Q 5 Nov 14 2014 Q3 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
	Sep. 30, 2014	Oct. 31, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'ava	'
Entity Registrant Name	'AVISTA CORP	'
Entity Central Index Key	'0000104918	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	62,239,441

Consolidated_Statements_Of_Inc

Consolidated Statements Of Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Common Stock, Dividends, Per Share, Cash Paid	$0.32	$0.31	$0.95	$0.92
Operating Revenues:	'	'	'	'
Utility revenues	$291,262	$278,473	$1,031,491	$1,007,319
Other non-utility revenues	10,296	11,004	29,225	30,145
Total operating revenues	301,558	289,477	1,060,716	1,037,464
Utility operating expenses:	'	'	'	'
Resource costs	131,588	131,136	481,007	487,277
Other operating expenses	72,509	69,596	207,195	200,824
Depreciation and amortization	33,294	29,823	95,200	86,783
Taxes other than income taxes	21,000	18,712	70,513	66,137
Other non-utility operating expenses:	'	'	'	'
Other operating expenses	10,251	10,212	20,514	28,972
Depreciation and amortization	154	171	452	536
Total operating expenses	268,796	259,650	874,881	870,529
Income from operations	32,762	29,827	185,835	166,935
Interest expense	18,642	19,168	55,933	57,854
Interest expense to affiliated trusts	113	117	336	352
Capitalized interest	-1,212	-820	-2,707	-2,702
Other income-net	-2,608	-488	-8,263	-4,439
Income before income taxes	17,827	11,850	140,536	115,870
Income tax expense	7,301	3,367	51,274	41,929
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	10,526	8,483	89,262	73,941
Net income	10,471	11,931	160,034	80,762
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	-55	3,448	70,772	6,821
Net income attributable to noncontrolling interests	-20	-518	-213	-1,351
Income (Loss) from Continuing Operations Attributable to Parent	10,506	8,450	89,236	73,882
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	-55	2,963	70,585	5,529
Net income attributable to Avista Corporation shareholders	$10,451	$11,413	$159,821	$79,411
Weighted-average common shares outstanding (thousands), basic	63,934	59,994	61,413	59,933
Weighted-average common shares outstanding (thousands), diluted	64,244	60,032	61,625	59,964
Income (Loss) from Continuing Operations, Per Basic Share	$0.16	$0.14	$1.45	$1.23
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	$0	$0.05	$1.15	$0.09
Earnings per common share attributable to Avista Corporation shareholders:	'	'	'	'
Basic (usd per share)	$0.16	$0.19	$2.60	$1.32
Diluted (usd per share)	$0.16	$0.19	$2.59	$1.32
Income (Loss) from Continuing Operations, Per Diluted Share	$0.16	$0.14	$1.45	$1.23
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$0	$0.05	$1.14	$0.09

Consolidated_Statements_Of_Com

Consolidated Statements Of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Net income	$10,471	$11,931	$160,034	$80,762
Other Comprehensive Income (Loss):	'	'	'	'
Unrealized investment gains/(losses) - net of taxes	0	-395	1,126	-1,687
Reclassification adjustment for realized gains on investment securities included in net income - net of taxes	0	-1	-2	-12
Reclassification adjustment for realized losses on investment securities net of taxes	'	'	462	0
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes	112	184	335	551
Total other comprehensive loss	112	-212	1,921	-1,148
Comprehensive income	10,583	11,719	161,955	79,614
Comprehensive income attributable to noncontrolling interests	-20	-518	-213	-1,351
Comprehensive income attributable to Avista Corporation shareholders	$10,563	$11,201	$161,742	$78,263

Consolidated_Statements_Of_Com1

Consolidated Statements Of Comprehensive Income (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Unrealized investment gains - taxes	$0	($233)	$664	($993)
Realized investment gains - taxes	0	-1	-1	-8
Realized investment losses - taxes	'	'	273	0
Change in unfunded benefit obligation for pension and other postretirement benefit plans - taxes	$60	$99	$181	$297

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current Assets:	'	'
Cash and cash equivalents	$10,391	$82,574
Accounts and notes receivable-less allowances of $4,331 and $44,309, respectively	124,550	221,343
Utility energy commodity derivative assets	3,334	3,022
Regulatory asset for utility derivatives	1,724	10,829
Investments and funds held for clients	0	96,688
Materials and supplies, fuel stock and natural gas stored	69,941	44,946
Deferred income taxes	8,316	24,788
Income taxes receivable	8,428	7,783
Other current assets	38,520	57,706
Total current assets	265,204	549,679
Net Utility Property:	'	'
Utility plant in service	4,655,329	4,290,464
Construction work in progress	205,572	160,323
Total	4,860,901	4,450,787
Less: Accumulated depreciation and amortization	1,322,927	1,248,362
Total net utility property	3,537,974	3,202,425
Other Non-current Assets:	'	'
Investment in exchange power-net	12,046	13,883
Investment in affiliated trusts	11,547	11,547
Goodwill	55,877	76,257
Intangible assets-net of accumulated amortization of $0 and $36,634, respectively	0	39,576
Long-term energy contract receivable of Spokane Energy	31,405	40,619
Other property and investments-net	41,331	58,555
Total other non-current assets	152,206	240,437
Deferred Charges:	'	'
Regulatory assets for deferred income tax	64,322	71,421
Regulatory assets for pensions and other postretirement benefits	151,647	156,984
Other regulatory assets	121,760	102,915
Non-current utility energy commodity derivative assets	1,693	854
Non-current regulatory asset for utility derivatives	13,153	23,258
Other deferred charges	28,387	13,950
Total deferred charges	380,962	369,382
Total assets	4,336,346	4,361,923
Current Liabilities:	'	'
Accounts payable	82,366	182,088
Client fund obligations	0	99,117
Current portion of long-term debt	6,471	358
Current portion of nonrecourse long-term debt of Spokane Energy	5,666	16,407
Short-term borrowings	35,000	171,000
Utility energy commodity derivative liabilities	5,009	10,875
Taxes Payable, Current	7,581	697
Other current liabilities	128,726	144,798
Total current liabilities	270,819	625,340
Long-term debt	1,412,211	1,272,425
Nonrecourse long-term debt of Spokane Energy	0	1,431
Long-term debt to affiliated trusts	51,547	51,547
Long-term borrowings under committed line of credit	0	46,000
Regulatory liability for utility plant retirement costs	254,162	242,850
Pensions and other postretirement benefits	95,037	122,513
Deferred income taxes	640,260	535,343
Other non-current liabilities and deferred credits	120,553	130,318
Total liabilities	2,844,589	3,027,767
Commitments and Contingencies (See Notes to Consolidated Financial Statements)	'	'
Redeemable Noncontrolling Interests	0	15,889
Avista Corporation Stockholders’ Equity:	'	'
Common stock, no par value; 200,000,000 shares authorized; 62,838,628 and 60,076,752 shares outstanding, respectively	1,007,764	896,993
Accumulated other comprehensive loss	-3,898	-5,819
Retained earnings	488,342	407,092
Total Avista Corporation stockholders’ equity	1,492,208	1,298,266
Noncontrolling Interests	-451	20,001
Total equity	1,491,757	1,318,267
Total liabilities and equity	$4,336,346	$4,361,923

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]	'	'
Accounts and notes receivable, allowances	$4,331	$44,309
Accumulated Amortization	$0	$36,634
Common stock, par value	$0	$0
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares outstanding	62,838,628	60,076,752

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Escrow receivable included in investing activities	$13,567	$0
Stock Issued During Period, Value, Acquisitions	150,075	0
Operating Activities:	'	'
Net income	160,034	80,762
Non-cash items included in net income:	'	'
Depreciation and amortization	102,899	98,793
Provision for deferred income taxes	111,335	16,512
Power and natural gas cost amortizations (deferrals), net	-17,956	-10,149
Amortization of debt expense	2,799	2,841
Amortization of investment in exchange power	1,838	1,838
Stock-based compensation expense	6,261	4,718
Equity-related AFUDC	-6,426	-4,341
Pension and other postretirement benefit expense	17,381	31,894
Amortization of Spokane Energy contract	9,214	8,470
Other Asset Impairment Charges	0	2,534
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	-161,100	0
Other	14,568	6,889
Contributions to defined benefit pension plan	-32,000	-44,000
Changes in working capital components:	'	'
Accounts and notes receivable	64,761	50,681
Materials and supplies, fuel stock and natural gas stored	-22,979	-9,388
Other current assets	3,447	-23,165
Accounts payable	-22,450	-23,756
Increase (Decrease) in Income Taxes Payable	6,885	303
Other current liabilities	27,203	10,966
Net cash provided by operating activities	265,714	202,402
Investing Activities:	'	'
Utility property capital expenditures (excluding equity-related AFUDC)	-229,764	-220,712
Other capital expenditures	-6,316	-1,725
Federal grant payments received	2,191	2,631
Payments to Acquire Businesses, Gross	15,007	0
Decrease (increase) In Money Market Funds Held For Clients	-18,931	11,723
Purchase of securities available for sale	-12,267	-35,949
Sale and maturity of securities available for sale	14,612	16,955
Proceeds from Divestiture of Businesses, Net of Cash Divested	229,903	0
Other	-1,194	-6,481
Net cash used in investing activities	-6,759	-233,558
Financing Activities:	'	'
Net increase (decrease) in short-term borrowings	-136,000	14,000
Borrowings from Ecova line of credit	0	3,000
Repayment of borrowings from Ecova line of credit	-46,000	-7,000
Proceeds from Issuance of Long-term Debt	75,000	90,000
Redemption and maturity of long-term debt	-39,367	-415
Maturity of nonrecourse long-term debt of Spokane Energy	-12,172	-11,115
Payments for (Proceeds from) Derivative Instrument, Financing Activities	0	2,901
Issuance of common stock	3,425	4,479
Payments for Repurchase of Common Stock	-60,963	0
Cash dividends paid	-58,552	-54,963
Increase in client fund obligations	16,216	7,375
Payments to Noncontrolling Interests	-54,179	0
Payments for Repurchase of Redeemable Noncontrolling Interest	-20,871	0
Other	2,325	-591
Net cash provided by (used in) financing activities	-331,138	47,671
Net increase (decrease) in cash and cash equivalents	-72,183	16,515
Cash and cash equivalents at beginning of period	82,574	75,464
Cash and cash equivalents at end of period	10,391	91,979
Cash paid during the year:	'	'
Interest	44,886	45,633
Income taxes	22,451	33,522
Non-cash financing and investing activities:	'	'
Accounts payable for capital expenditures	6,945	4,313
Redeemable noncontrolling interests	($15,873)	$3,246

Consolidated_Statements_Of_Equ

Consolidated Statements Of Equity And Redeemable Noncontrolling Interests (USD $)	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]	Redeemable Noncontrolling Interests [Member]
In Thousands, except Share data
Beginning Balance at Dec. 31, 2012	'	$889,237	($6,700)	$376,940	$17,658	$4,938
Beginning Balance (in shares) at Dec. 31, 2012	'	59,812,796	'	'	'	'
Noncontrolling Interest, Decrease from Deconsolidation	0	'	'	'	'	'
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable	'	'	'	'	'	119
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable	'	'	'	'	1,232	'
Issuance of common stock	'	216,413	'	'	'	'
Equity compensation expense	'	4,490	'	'	'	'
Issuance of common stock, net of issuance costs	'	4,479	'	'	'	'
Stock Repurchased During Period, Value	'	0	'	0	'	'
Equity transactions of consolidated subsidiaries	'	-7	'	'	'	'
Other comprehensive loss	-1,148	'	-1,148	'	'	'
Net income attributable to Avista Corporation shareholders	79,411	'	'	79,411	'	'
Cash dividends paid (common stock)	'	'	'	-54,963	'	'
Total equity	1,310,457	'	'	'	'	'
Other	'	'	'	'	2,163	'
Purchase of subsidiary noncontrolling interests	'	'	'	'	'	-379
Valuation adjustments and other noncontrolling interests activity	'	'	'	-2,335	'	3,652
Payments for Repurchase of Redeemable Noncontrolling Interest	0	'	'	'	'	'
Excess Tax Benefit from Share-based Compensation, Financing Activities	0	'	'	'	'	'
Stock Repurchased During Period, Shares	'	0	'	'	'	'
Ending Balance at Sep. 30, 2013	1,289,404	898,199	-7,848	399,053	21,053	8,330
Ending Balance (in shares) at Sep. 30, 2013	'	60,029,209	'	'	'	'
Beginning Balance at Dec. 31, 2013	1,298,266	896,993	-5,819	407,092	20,001	15,889
Beginning Balance (in shares) at Dec. 31, 2013	60,076,752	60,076,752	'	'	'	'
Noncontrolling Interest, Decrease from Deconsolidation	-23,612	'	'	'	'	'
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable	'	'	'	'	'	-4
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable	'	'	'	'	217	'
Issuance of common stock	'	4,685,953	'	'	'	'
Equity compensation expense	'	6,061	'	'	'	'
Issuance of common stock, net of issuance costs	'	153,501	'	'	'	'
Stock Repurchased During Period, Value	'	-30,794	'	-30,169	'	'
Equity transactions of consolidated subsidiaries	'	-1,062	'	'	'	'
Other comprehensive loss	1,921	'	1,921	'	'	'
Net income attributable to Avista Corporation shareholders	159,821	'	'	159,821	'	'
Cash dividends paid (common stock)	'	'	'	-58,552	'	'
Total equity	1,491,757	'	'	'	'	'
Other	'	'	'	'	2,943	'
Purchase of subsidiary noncontrolling interests	'	'	'	'	'	-12
Valuation adjustments and other noncontrolling interests activity	'	'	'	10,150	'	-15,873
Payments for Repurchase of Redeemable Noncontrolling Interest	-20,871	'	'	'	'	'
Excess Tax Benefit from Share-based Compensation, Financing Activities	3,936	'	'	'	'	'
Stock Repurchased During Period, Shares	'	-1,924,077	'	'	'	'
Ending Balance at Sep. 30, 2014	$1,492,208	$1,007,764	($3,898)	$488,342	($451)	$0
Ending Balance (in shares) at Sep. 30, 2014	62,838,628	62,838,628	'	'	'	'

Summary_Of_Significant_Account

Summary Of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2014
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 the 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 Avista Utilities' Noxon Rapids generating facility.
	On July 1, 2014, Avista Corp. completed its acquisition of Alaska Energy and Resources Company (AERC), and as of that date, AERC is a wholly-owned subsidiary of Avista Corp. The primary subsidiary of AERC is Alaska Electric Light and Power Company (AEL&P), comprising the regulated utility operations in Alaska. Beginning with the three months ended September 30, 2014, the results of AERC are included in the overall results of Avista Corp. See Note 4 for information regarding the acquisition of AERC.
	Avista Capital, Inc. (Avista Capital), a wholly owned subsidiary of Avista Corp., is the parent company of all of the subsidiary companies in the non-utility businesses, except Spokane Energy, LLC (Spokane Energy). During the first half of the year, Avista Capital’s subsidiaries included Ecova, Inc. (Ecova), which was an 80.2 percent owned subsidiary prior to its disposition on June 30, 2014. Ecova was a provider of energy efficiency and other facility information and cost management programs and services for multi-site customers and utilities throughout North America. See Note 5 for information regarding the disposition of Ecova and Note 13 for business segment information.
	Basis of Reporting
	The condensed consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Ecova's revenues and expenses are included in the Condensed Consolidated Statements of Income in discontinued operations; however, as of June 30, 2014 and for all subsequent reporting periods there are no balance sheet amounts included for Ecova. 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.
	Taxes Other Than Income Taxes
	Taxes other than income taxes include state excise taxes, city occupational and franchise taxes, real and personal property taxes and certain other taxes not based on net income. These taxes are generally based on revenues or the value of property. Utility related taxes collected from customers (primarily state excise taxes and city utility taxes) are recorded as operating revenue and expense and totaled the following amounts for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Utility taxes	$	11,716			$	10,901			$	43,923			$	41,045
	Other Income-Net
	Other income-net consisted of the following items for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Interest income	$	154			$	124			$	678			$	620
	Interest income on regulatory deferrals	59				27				154				48
	Equity-related AFUDC	2,189				1,595				6,426				4,341
	Net gain/(loss) on investments	(27		)		(1,299		)		118				(1,543		)
	Other income	233				41				887				973
	Total	$	2,608			$	488			$	8,263			$	4,439
	The prior period amounts included in the table above were revised to include only the amounts related to continuing operations. All other amounts were reclassified to discontinued operations.
	Materials and Supplies, Fuel Stock and Natural Gas Stored
	Inventories of materials and supplies, fuel stock and natural gas stored 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 September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,				December 31,
		2014				2013
	Materials and supplies	$	31,226			$	28,747
	Fuel stock	5,170				3,170
	Natural gas stored	33,545				13,029
	Total	$	69,941			$	44,946
	Investments and Funds Held for Clients and Client Fund Obligations
	In connection with its bill paying services, Ecova collected funds from its clients and remitted the funds to the appropriate utility or other service provider. Some of the funds collected were invested by Ecova and classified as investments and funds held for clients, and a related liability for client fund obligations was recorded. Investments and funds held for clients included cash and cash equivalent investments, money market funds and investment securities classified as available for sale. Ecova did not invest the funds directly for the clients' benefit; therefore, Ecova bore the risk of loss associated with the investments. As of June 30, 2014 and for all subsequent reporting periods there are no longer any investments and funds held for clients due to the disposition of Ecova.
	Investments and funds held for clients as of December 31, 2013 were as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	16,147			$	—			$	16,147
	Money market funds	11,180				—				11,180
	Securities available for sale:
	U.S. government agency	63,633				(2,555		)		61,078
	Municipal	3,497				21				3,518
	Corporate fixed income – financial	3,000				—				3,000
	Corporate fixed income – industrial	753				12				765
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	71,883				(2,522		)		69,361
	Total investments and funds held for clients	$	99,210			$	(2,522	)		$	96,688
	-1	Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.
	Investments and funds held for clients were classified as a current asset since these funds were held for the purpose of satisfying the client fund obligations. As of December 31, 2013, approximately 95 percent of the investment portfolio was rated AA-, Aa3 and higher by nationally recognized statistical rating organizations. All fixed income securities were rated as investment grade as of December 31, 2013.
	Ecova management reviewed its investments continuously for indicators of other-than-temporary impairment. To make this determination, management employed a methodology that considers available quantitative and qualitative evidence in evaluating potential impairment of its investments. If the cost of an investment exceeded its fair value, management evaluated, among other factors, general market conditions, credit quality of instrument issuers, the length of time and extent to which the fair value was less than cost, and whether it had plans to sell the security or it was more-likely-than not that the Company would be required to sell the security before recovery. Management also considered specific adverse conditions related to the financial health of and specific prospects for the issuer as well as other cash flow factors. Once a decline in fair value was determined to be other-than-temporary, an impairment charge was recorded in earnings and a new cost basis in the investment was established. Based on management’s analysis, securities available for sale did not meet the criteria for other-than-temporary impairment as of December 31, 2013.
	The following is a summary of the disposition of available-for-sale securities for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Proceeds from sales, maturities and calls	$	—			$	1,825			$	14,612			$	16,955
	Gross realized gains	—				2				3				20
	Gross realized losses (1)	—				—				(735		)		—
	-1	The gross realized losses for the nine months ended September 30, 2014 were included in the determination of the gain on the disposal of Ecova and were not the result of selling any individual securities.
	Contractual maturities of securities available for sale as of December 31, 2013 are as follows (dollars in thousands):
		Due within 1 year			After 1 but within 5 years			After 5 but within 10 years			After 10 years			Total
	31-Dec-13	5,382			12,745			48,310			2,924			69,361
	Actual maturities may differ due to call or prepayment rights and the effective maturity was 3.0 years as of December 31, 2013.
	Goodwill
	Goodwill arising from acquisitions represents the excess of the purchase price over the estimated fair value of net assets acquired. The Company evaluates goodwill for impairment using a combination of the discounted cash flow model and a market approach on at least an annual basis or more frequently if impairment indicators arise. The Company completed its annual evaluation of goodwill for potential impairment as of December 31, 2013 for Ecova and as of November 30, 2013 for the other businesses and determined that goodwill was not impaired at that time. Avista Corp. will use November 30, 2014 for its annual evaluation of goodwill related to AEL&P and the other businesses for 2014.
	The changes in the carrying amount of goodwill are as follows (dollars in thousands):
	Ecova				AEL&P				Other				Accumulated				Total
													Impairment
													Losses
31-Dec-13	$	71,011			$	—			$	12,979			$	(7,733	)		$	76,257
Adjustments	112				—				—				—				112
Goodwill sold during the year	(71,123		)		—				—				—				(71,123		)
Goodwill acquired during the year	—				50,631				—				—				50,631
Balance as of September 30, 2014	$	—			$	50,631			$	12,979			$	(7,733	)		$	55,877
Accumulated impairment losses are attributable to the other businesses. The goodwill sold during the year relates to the Ecova disposition, which occurred on June 30, 2014. See Note 5 for information regarding this sales transaction. The goodwill acquired during the year relates to the acquisition of AERC and the goodwill associated with this acquisition is not deductible for tax purposes. See Note 4 for information regarding this business acquisition and Note 13 regarding the Company's reportable segments.
Intangible Assets
Amortization expense related to intangible assets was as follows for the three and nine months ended September 30 (dollars in thousands):
	Three months ended September 30,								Nine months ended September 30,
	2014				2013				2014				2013
Intangible asset amortization	$	—			$	2,765			$	5,898			$	8,442
All of the intangible assets were related to Ecova, which was disposed of as of June 30, 2014. As such, there are no intangible assets remaining as of September 30, 2014 and there is no amortization expense expected for the remainder of the year and in future years. The amortization expense disclosed in the table above is included in discontinued operations for all periods presented. See Note 5 for information regarding the Ecova sales transaction.
The gross carrying amount and accumulated amortization of intangible assets as of December 31, 2013 are as follows (dollars in thousands):
	Estimated		December 31,
	Useful Lives		2013
Client relationships	2 - 12 years		$	33,562
Software development costs	3 - 7 years		39,327
Other	1 - 10 years		3,321
Total intangible assets			76,210
Client relationships accumulated amortization			(12,336		)
Software development costs accumulated amortization			(21,861		)
Other accumulated amortization			(2,437		)
Total accumulated amortization			(36,634		)
Total intangible assets - net			$	39,576
Derivative Assets and Liabilities
Derivatives are recorded as either assets or liabilities on the Condensed Consolidated Balance Sheets measured at estimated fair value. In certain defined conditions, a derivative may be specifically designated as a hedge for a particular exposure. The accounting for a derivative depends on the intended use of such derivative and the resulting designation.
The Washington Utilities and Transportation Commission (UTC) and the Idaho Public Utilities Commission (IPUC) issued accounting orders authorizing Avista Utilities 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. The orders provide for Avista Utilities to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the periods of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the Energy Recovery Mechanism (ERM) in Washington, the Power Cost Adjustment (PCA) mechanism in Idaho, and periodic general rates cases. Regulatory assets are assessed regularly and are probable for 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 agreements, each period Avista Utilities records all mark-to-market gains and losses for its interest rate swaps agreements as assets and liabilities and records offsetting regulatory assets and liabilities, such that there is no income statement impact. This is similar to the treatment of energy commodity derivatives described above. Upon settlement of interest rate swaps, the regulatory asset or liability (included as part of long-term debt) is amortized as a component of interest expense over the term of the associated debt.
Fair Value Measurements
Fair value represents the price that would be received to sell 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, investments and funds held for clients, deferred compensation assets, as well as derivatives related to interest rate swap agreements and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 10 for the Company’s fair value disclosures.
Regulatory Deferred Charges and Credits
The Company prepares its condensed consolidated financial statements in accordance with regulatory accounting practices because:
•	rates for regulated services are established by or subject to approval by independent third-party regulators,
•	the regulated rates are designed to recover the cost of providing the regulated services, and
•	in view of demand for the regulated services and the level of competition, it is reasonable to assume that rates can be charged to and collected from customers at levels that will recover costs.
Regulatory accounting practices require that certain costs and/or obligations (such as incurred power and natural gas costs not currently included in rates, but expected to be recovered or refunded in the future) are reflected as deferred charges or credits on the Condensed Consolidated Balance Sheets. These costs and/or obligations are not reflected in the Condensed Consolidated Statements of Income until the period during which matching revenues are recognized. If at some point in the future the Company determines that it no longer meets the criteria for continued application of regulatory accounting practices for all or a portion of its regulated operations, the Company could be:
•	required to write off its regulatory assets, and
•	precluded from the future deferral of costs not recovered through rates at the time such costs are incurred, even if the Company expected to recover such costs in the future.
Redeemable Noncontrolling Interests
At December 31, 2013, certain option holders of Ecova had the right to put their shares back to Ecova at their discretion during an annual put window. Stock options and other outstanding redeemable stock were valued at their maximum redemption amount which was equal to their intrinsic value (fair value less exercise price). Due to the disposition of Ecova, as of June 30, 2014 there are no longer any redeemable noncontrolling interests.
Accumulated Other Comprehensive Loss
Accumulated other comprehensive loss, net of tax, consisted of the following as of September 30, 2014 and December 31, 2013 (dollars in thousands):
	September 30,				December 31,
	2014				2013
Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $(2,099) and $(2,280), respectively	$	(3,898	)		$	(4,233	)
Unrealized loss on securities available for sale - net of taxes of $0 and $(936), respectively (1)	—				(1,586		)
Total accumulated other comprehensive loss	$	(3,898	)		$	(5,819	)
-1	This entire balance was related to Ecova, which was disposed of as of June 30, 2014.
The following table details the reclassifications out of accumulated other comprehensive loss by component for the three and nine months ended September 30 (dollars in thousands):
		Amounts Reclassified from Accumulated Other Comprehensive Loss
		Three months ended September 30,								Nine months ended September 30,
Details about Accumulated Other Comprehensive Loss Components		2014				2013				2014				2013				Affected Line Item in Statement of Income
Realized gains on investment securities		$	—			$	2			$	3			$	20			(a)
Realized losses on investment securities		—				—				(735		)		—				(a)
		—				2				(732		)		20				Total before tax
		—				(1		)		272				(8		)		Tax benefit (expense) (a)
		$	—			$	1			$	(460	)		$	12			Net of tax
Amortization of defined benefit pension items
Amortization of net loss		$	(1,951	)		$	(4,891	)		$	(5,855	)		$	(14,673	)		(b)
Adjustment due to effects of regulation		1,779				4,608				5,339				13,825				(b)
		(172		)		(283		)		(516		)		(848		)		Total before tax
		60				99				181				297				Tax benefit
		$	(112	)		$	(184	)		$	(335	)		$	(551	)		Net of tax
(a)	These amounts were included as part of net income from discontinued operations for all periods presented (see Note 5 for additional details).
(b)	These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details).
Appropriated Retained Earnings
In accordance with the hydroelectric licensing requirements of section 10(d) of the Federal Power Act (FPA), the Company maintains an appropriated retained earnings account for any earnings in excess of the specified rate of return on the Company's investment in the licenses for its various hydroelectric projects. The rate of return on investment is specified in the various hydroelectric licensing agreements for the Clark Fork River and Spokane River. Per section 10(d) of the FPA, the Company must maintain these excess earnings in an appropriated retained earnings account until the termination of the licensing agreements or apply them to reduce the net investment in the licenses of the hydroelectric projects at the discretion of the FERC. The Company typically calculates the earnings in excess of the specified rate of return on an annual basis, usually during the second quarter.
In addition to the hydroelectric project licenses identified above for Avista Utilities, the requirements of section 10(d) of the FPA also apply to the Lake Dorothy, the Annex Creek and the Salmon Creek licenses, which were all acquired in the AERC acquisition. The Company is still evaluating these licenses to determine an appropriate amount of appropriated retained earnings to record and this analysis is expected to be completed in 2015. The Company does not expect this to result in a material amount of appropriated retained earnings.
The appropriated retained earnings amounts included in retained earnings were as follows as of September 30, 2014 and December 31, 2013 (dollars in thousands):
	September 30,				December 31,
	2014				2013
Appropriated retained earnings	$	14,270			$	9,714
Dividends
The payment of dividends on common stock could be limited by:
•	certain covenants applicable to preferred stock (when outstanding) contained in the Company’s Restated Articles of Incorporation, as amended (currently there are no preferred shares outstanding),
•	certain covenants applicable to the Company's outstanding long-term debt and committed line of credit agreements,
•	the hydroelectric licensing requirements of section 10(d) of the FPA, and
•	certain requirements under the OPUC approval of the AERC acquisition, which does not permit one-time or special dividends from AERC to Avista Corp. and which does not permit Avista Utilities' total equity to total capitalization to be less than 40 percent, without approval from the OPUC. The OPUC approval does allow for special or one-time dividends during the first year after closing to recapitalize AERC as part of the transaction and it also allows for regular distributions of AERC earnings to Avista Corp. as long as AERC remains sufficiently capitalized and insured.
Under the covenant applicable to the Company's committed line of credit agreement, which does not permit the ratio of “consolidated total debt” to “consolidated total capitalization” to be greater than 65 percent at any time, the amount of retained earnings available for dividends at September 30, 2014 was limited to approximately $441.1 million.
Under the requirements of the OPUC approval of the AERC acquisition as outlined above, the amount available for dividends at September 30, 2014 was limited to approximately $291.0 million.
Stock Repurchase Program
On June 13, 2014, Avista Corp.'s Board of Directors approved a program to repurchase up to 4 million shares of the Company’s outstanding common stock, assuming the closure of the Ecova transaction. Repurchases of common stock under this program commenced on July 7, 2014 and the program expires on December 31, 2014. The Company can choose to terminate the repurchase program before December 31, 2014. Repurchases are made in the open market or in privately negotiated transactions. There is no assurance that the goal of repurchasing 4 million shares will be achieved. Through October 31, 2014, the Company has repurchased 2,529,615 shares at a total cost of $79.9 million and an average cost of $31.57 per share. All repurchased shares revert to the status of authorized but unissued shares.
The following table provides information about share repurchases that Avista Corp. made during the three months ended September 30, 2014 (in thousands, except per share amounts):
	Total Number of Shares Purchased			Average Price Paid per Share				Total Number of Shares Purchased as Part of Publicly Announced Program			Maximum Number of Shares that May Yet Be Purchased Under the Program
July 1 to July 31, 2014	292			$	32.3			292			3,708
August 1 to August 31, 2014	927			31.5				927			2,781
September 1 to September 30, 2014	705			31.67				705			2,076
Total	1,924			$	31.68			1,924			2,076
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 losses that do not meet these conditions for accrual, if there is a reasonable possibility that a loss may be incurred.

New_Accounting_Standards

New Accounting Standards	9 Months Ended
	Sep. 30, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
New Accounting Standards	'
	NEW ACCOUNTING STANDARDS
	In April 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-08, "Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity." This ASU amends the definition of a discontinued operation and requires entities to provide additional disclosures about discontinued operations as well as disposal transactions that do not meet the discontinued-operations criteria. ASU 2014-08 makes it more difficult for a disposal transaction to qualify as a discontinued operation. In addition, the ASU requires entities to reclassify assets and liabilities of a discontinued operation for all comparative periods presented in the Balance Sheet rather than just the current period and it requires additional disclosures on the face of the Statement of Cash Flows regarding discontinued operations. This ASU is effective for periods beginning on or after December 15, 2014; however, early adoption is permitted. The Company has evaluated this standard and determined that it will not early adopt this standard. As such, there is no impact to the Company's financial condition, results of operations and cash flows in the current year.
	In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers (Topic 606)," which outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that an entity identifies the various performance obligations in a contract, allocates the transaction price among the performance obligations and recognizes revenue as the entity satisfies the performance obligations. This ASU is effective for periods beginning after December 15, 2016 and early adoption is not permitted. However, while this ASU is not effective until 2017, it will require retroactive application to all periods presented in the financial statements. As such, at adoption in 2017, amounts in 2015 and 2016 may have to be revised or a cumulative adjustment to opening retained earnings may have to be recorded. The Company is currently evaluating this standard and cannot, at this time, estimate the potential impact to its future financial condition, results of operations and cash flows.
	In August 2014, the FASB issued ASU No. 2014-15, "Presentation of Financial Statements - Going Concern (ASC Subtopic 205-40): Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern." The new standard provides guidance around management's responsibility to evaluate whether there is substantial doubt about an entity's ability to continue as a going concern within one year of the date the financial statements are issued. The Company must provide certain disclosures if conditions or events raise substantial doubt about the Company’s ability to continue as a going concern. The new standard is effective for periods beginning after December 15, 2016; however, early adoption is permitted. The Company has evaluated this standard and determined that it will not early adopt this standard. As such, there is no impact to the Company's financial condition, results of operations and cash flows in the current year.

Variable_Interest_Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2014
Variable Interest Entities [Abstract]	'
Variable Interest Entities	'
	VARIABLE INTEREST ENTITIES
	Lancaster Power Purchase Agreement
	The Company has a power purchase agreement (PPA) for all the output of the Lancaster Plant, a 270 MW natural gas-fired combined cycle combustion turbine plant located in Kootenai County, Idaho, owned by an unrelated third-party (Rathdrum Power LLC), through 2026.
	Avista Corp. has a variable interest in the PPA. Accordingly, Avista Corp. made an evaluation of which interest holders have the power to direct the activities that most significantly impact the economic performance of the entity and which interest holders have the obligation to absorb losses or receive benefits that could be significant to the entity. Avista Corp. pays a fixed capacity and operations and maintenance payment and certain monthly variable costs under the PPA. Under the terms of the PPA, Avista Corp. makes the dispatch decisions, provides all natural gas fuel and receives all of the electric energy output from the Lancaster Plant. However, Rathdrum Power LLC (the owner) controls the daily operation of the Lancaster Plant and makes operating and maintenance decisions. Rathdrum Power LLC controls all of the rights and obligations of the Lancaster Plant after the expiration of the PPA in 2026. It is estimated that the plant will have 15 to 25 years of useful life after that time. Rathdrum Power LLC bears the maintenance risk of the plant and will receive the residual value of the Lancaster Plant. Avista Corp. has no debt or equity investments in the Lancaster Plant and does not provide financial support through liquidity arrangements or other commitments (other than the PPA). Based on its analysis, Avista Corp. does not consider itself to be the primary beneficiary of the Lancaster Plant. Accordingly, neither the Lancaster Plant nor Rathdrum Power LLC is included in Avista Corp.’s condensed consolidated financial statements. The Company has a future contractual obligation of approximately $280.9 million under the PPA (representing the fixed capacity and operations and maintenance payments through 2026) and believes this would be its maximum exposure to loss. However, the Company believes that such costs will be recovered through retail rates.
	Palouse Wind Power Purchase Agreement
	In June 2011, the Company entered into a 30-year PPA with Palouse Wind, LLC (Palouse Wind), an affiliate of First Wind Holdings, LLC. The PPA relates to a wind-driven power generation project that was developed by Palouse Wind in Whitman County, Washington and under the terms of the PPA, the Company acquires all of the power and renewable attributes produced by the wind project for a fixed price per MWh, which escalates annually, without consideration for market fluctuations. The wind project has a nameplate capacity of approximately 105 MW and is expected to produce approximately 40 aMW annually. The project was completed and energy deliveries began during the fourth quarter of 2012. Under the PPA, the Company has an annual option to purchase the wind project following the 10th anniversary of the commercial operation date at a fixed price determined under the contract.
	The Company evaluated this agreement to determine if it has a variable interest which must be consolidated. Based on its analysis, Avista Corp. does not consider itself to be the primary beneficiary of the Palouse Wind facility due to the fact that it pays a fixed price per MWh, which represents the only financial obligation, and does not have any input into the management of the day-to-day operations of the facility. Accordingly, Palouse Wind is not included in Avista Corp.’s condensed consolidated financial statements. The Company has a future contractual obligation of approximately $590.6 million under the PPA (representing the charges associated with purchasing the energy and renewable attributes through 2042) and believes this would be its maximum exposure to loss. However, the Company believes that such costs will be recovered through retail rates.

Business_Acquisitions

Business Acquisitions	9 Months Ended
	Sep. 30, 2014
Business Acquisitions [Abstract]	'
Business Combination Disclosure	'
	BUSINESS ACQUISITIONS
	Alaska Energy and Resources Company
	On July 1, 2014, the Company completed its acquisition of AERC, based in Juneau, Alaska. As of July 1, 2014 AERC is a wholly-owned subsidiary of Avista Corp.
	The primary subsidiary of AERC is AEL&P, a regulated utility which provides electric services to approximately 16,000 customers in the City and Borough of Juneau (CBJ), Alaska. As of July 1, 2014, AEL&P had 60 full-time employees. Its rate base for 2013 was $109.0 million. AEL&P has a firm retail peak load of approximately 68 MW. AEL&P owns four hydroelectric generating facilities, having a total present capacity of 24.7 MW, and has a power purchase commitment for the output of the Snettisham hydroelectric project, having a present capacity of 78 MW, for a total hydroelectric capacity of 102.7 MW. AEL&P is not interconnected to any other electric system. AEL&P also has 93.9 MW of diesel generating capacity to provide back-up service to firm customers when necessary.
	In addition to the regulated utility, AERC owns AJT Mining Properties, Inc. (AJT Mining), which is an inactive mining company holding certain properties.
	The purpose of the acquisition was to expand and diversify Avista Corp.'s energy assets and deliver long-term value to its customers, communities and investors.
	In connection with the closing, Avista Corp. issued 4,500,014 new shares of common stock to the shareholders of AERC based on a contractual price formula which was $32.46 per share. The exchange for AERC shares for Avista Corp. shares reflects a purchase price of $170.0 million, plus acquired cash, less outstanding debt and other closing adjustments.
	The $32.46 price per share of Avista Corp. common stock was determined based on the average closing stock price of Avista Corp. common stock for the 10 consecutive trading days immediately preceding, but not including, the trading day prior to July 1, 2014. This value was used solely for determining the number of shares to issue based on the adjusted contract closing price (see reconciliation below). The fair value of the consideration transferred was based on the closing stock price of Avista Corp. common stock on July 1, 2014, which was $33.35 per share.
	The contract acquisition price and the fair value of consideration transferred for AERC as of July 1, 2014 were as follows (in thousands):
		1-Jul-14
	Contract acquisition price (using the calculated $32.46 per share common stock price)
	Gross contract price	$	170,000
	Acquired cash	19,704
	Acquired debt (excluding capital lease obligation)	(38,832		)
	Other closing adjustments	(104		)
	Total adjusted contract price	$	150,768
	Fair value of consideration transferred
	Avista Corp. common stock (4,500,014 shares at $33.35 per share)	$	150,075
	Cash	4,697
	Fair value of total consideration transferred	$	154,772
	The preliminary estimated fair value of assets acquired and liabilities assumed as of July 1, 2014 were as follows (in thousands):
		1-Jul-14
	Assets acquired:
	Current Assets:
	Cash	$	19,704
	Accounts receivable - gross totals $3,928	3,851
	Materials and supplies	2,017
	Other current assets	999
	Total current assets	26,571
	Utility Property:
	Utility plant in service	113,964
	Utility property under long-term capital lease	71,007
	Construction work in progress	3,440
	Total utility property	188,411
	Other Non-current Assets:
	Non-utility property	6,660
	Electric plant held for future use	3,711
	Goodwill	50,631
	Other deferred charges and non-current assets	5,368
	Total other non-current assets	66,370
	Total assets	$	281,352
	Liabilities Assumed:
	Current Liabilities:
	Accounts payable	$	700
	Current portion of long-term debt and capital lease obligations	3,773
	Other current liabilities	2,902
	Total current liabilities	7,375
	Long-term debt	37,227
	Capital lease obligations	68,840
	Other non-current liabilities and deferred credits	13,138
	Total liabilities	$	126,580
	Total identifiable net assets acquired	$	154,772
	The goodwill associated with this acquisition is not deductible for tax purposes.
	The majority of AERC’s operations are subject to the rate-setting authority of the Regulatory Commission of Alaska (RCA) and are accounted for pursuant to U.S. GAAP, including the accounting guidance for regulated operations. The rate-setting and cost recovery provisions currently in place for AERC’s regulated operations provide revenues derived from costs, including a return on investment, of assets and liabilities included in rate base. Due to this regulation, the fair values of AERC’s assets and liabilities subject to these rate-setting provisions are assumed to approximate their carrying values. There were not any identifiable intangible assets associated with this acquisition. The excess of the purchase consideration over the estimated fair values of the assets acquired and liabilities assumed was recognized as goodwill at the acquisition date. The goodwill reflects the value paid for the expected continued growth of a rate-regulated business located in a defined service area with a constructive regulatory environment, the attractiveness of stable, growing cash flows, as well as providing a platform for potential future growth outside of the rate-regulated electric utility in Alaska.
	The following table summarizes the supplemental pro forma revenue, net income and earnings per share information for the three and nine months ended September 30 related to the acquisition of AERC as if the acquisition had occurred on January 1, 2013. The revenues and net income for AERC for the three months ended September 30, 2014 are actual results and the results for the first nine months of 2013 and the first six months of 2014 are pro forma results (dollars in thousands):
		Three months ended September 30,					Nine months ended September 30,
		2014			2013		2014		2013
	Actual Avista Corp. revenues from continuing operations (excluding AERC)	$	292,334		$	289,477	$	1,051,492	$	1,037,464
	Supplemental pro forma AERC revenues (1)	9,224			9,309		35,319		31,243
	Total supplemental pro forma revenues	301,558			298,786		1,086,811		1,068,707
	Actual AERC revenues included in Avista Corp. revenues (1)	9,224			—		9,224		—
	Actual Avista Corp. net income from continuing operations attributable to Avista Corp. shareholders (excluding AERC)	9,982			8,450		88,712		73,882
	Actual Avista Corp. net income from discontinued operations attributable to Avista Corp. shareholders	(55		)	2,963		70,585		5,529
Adjustment to Avista Corp.'s net income for acquisition costs (net of tax) (2)	401			66		838		(1,828		)
Supplemental pro forma AERC net income (1) (5)	524			199		6,151		7,634
Total supplemental pro forma net income	10,852			11,678		166,286		85,217
Actual AERC net income included in Avista Corp. net income (1)	$	524		$	—	$	524	$	—
Pro forma weighted-average common shares outstanding (thousands), basic (3)	63,934			64,494		64,413		64,433
Pro forma weighted-average common shares outstanding (thousands), diluted (3)	64,244			64,532		64,625		64,464
Pro forma earnings per common share attributable to Avista Corp. shareholders
Total pro forma earnings per common share attributable to Avista Corp. shareholders, basic	$	0.17		$	0.18	$	2.58	$	1.32
Total pro forma earnings per common share attributable to Avista Corp. shareholders, diluted (4)	$	0.17		$	0.18	$	2.57	$	1.32
-1	AERC was acquired on July 1, 2014 and only the supplemental revenues and net income from the third quarter of 2014 were included in the actual results of Avista Corp. for the three and nine months ended September 30.
-2	This adjustment is to treat all transaction costs incurred since the beginning of the transaction to January 1, 2013 as if the acquisition occurred on that date and to remove them from the periods in which they actually occurred. The transaction costs were expensed and presented in the Condensed Consolidated Statements of Income in other operating expenses within utility operating expenses. Since the start of the planned transaction through September 30, 2014, Avista Corp. has expensed $2.9 million (pre-tax) in total transaction fees associated with the transaction. In addition to the amounts expensed, Avista Corp. has included $0.4 million in fees through September 30, 2014 associated with the issuance of common stock for the transaction as a reduction to common stock. These fees do not impact the supplemental pro forma information above.
-3	The 4.5 million shares issued on July 1, 2014 for the acquisition of AERC were assumed to be issued on January 1, 2013 for purposes of calculating the pro forma weighted average shares outstanding.
-4	The pro forma diluted earnings per share calculation ignores the impact of the subsidiary earnings adjustment for dilutive securities for discontinued operations as disclosed at Note 11. Earnings per Common Share Attributable to Avista Corp. Shareholders. Including this dilutive impact would not change the diluted pro forma earnings per share amount disclosed above.
-5	The net income for the nine months ended September 30, 2013 at AERC includes a gain on the sale of property of approximately $2.3 million that does not occur every year.

Discontinued_Operations_Discon

Discontinued Operations Discontinued Operations (Notes)	9 Months Ended
	Sep. 30, 2014
Discontinued Operations [Abstract]	'
Disposal Groups, Including Discontinued Operations, Disclosure	'
	DISCONTINUED OPERATIONS
	On May 29, 2014, Avista Capital, the non-regulated subsidiary of Avista Corp., entered into a definitive agreement to sell its interest in Ecova to Cofely USA Inc., an indirect subsidiary of GDF SUEZ, a French multinational utility company, and an unrelated party to Avista Corp. The sales transaction was completed on June 30, 2014 for a sales price of $335.0 million in cash, less the payment of debt and other customary closing adjustments. At the closing of the transaction on June 30, 2014, Ecova became a wholly-owned subsidiary of Cofely USA Inc. and the Company will have no further involvement with Ecova after such date.
	The purchase price of $335.0 million, as adjusted, was divided among the security holders of Ecova, including minority shareholders and option holders, pro rata based on ownership. Approximately $16.8 million (5 percent of the purchase price) will be held in escrow for 15 months from the closing of the transaction to satisfy certain indemnification obligations under the merger agreement, and an additional $1.5 million will be held in escrow pending resolution of adjustments to working capital (which is expected to occur before the end of 2014).
	Avista Capital and Cofely USA Inc. agreed to make an election under Section 338(h)(10) of the Internal Revenue Code (Code) of 1986, as amended, with respect to the purchase and sale of Ecova to allocate the merger consideration among the assets of Ecova deemed to have been acquired in the merger.
	When all escrow amounts are released, the sales transaction is expected to provide cash proceeds to Avista Corp., net of debt, payment to option and minority holders, income taxes and transaction expenses, of $133.2 million (see reconciliation below) and result in a net gain of $68.0 million. The Company expects to receive the full amount of its portion of the escrow accounts; therefore, the full amounts were included in the gain calculation.
	The summary of cash proceeds associated with the sales transaction are as follows (in thousands):
		30-Jun-14
	Reconciliation to Statement of Cash Flows
	Contract price	$	335,000
	Closing adjustments	4,402
	Gross proceeds from sale (1)	339,402
	Cash sold in the transaction	(95,932		)
	Avista Corp. portion of proceeds held in escrow	(13,567		)
	Gross proceeds from sale of Ecova, net of cash sold (per Statement of Cash Flows)	$	229,903
	Reconciliation of expected net proceeds
	Gross proceeds from sale (1)	$	339,402
	Repayment of long-term borrowings under committed line of credit	(40,000		)
	Payment to option holders and redeemable noncontrolling interests	(20,871		)
	Payment to noncontrolling interests	(54,179		)
	Transaction expenses withheld from proceeds	(5,390		)
	Avista Corp. portion of proceeds held in escrow	(13,567		)
	Net proceeds to Avista Capital at transaction closing	205,395
	Estimated tax payments to be made in 2014	(85,756		)
	Avista Corp. portion of proceeds held in escrow to be received in the future	13,567
	Total net proceeds related to sales transaction	$	133,206
	-1	Of this total amount, approximately $16.8 million will be held in escrow for 15 months from the transaction closing date for any indemnity claims and an additional $1.5 million will be held in escrow pending resolution of adjustments to working capital (which is expected to occur before the end of 2014).
	Prior to the completion of the sales transaction, Ecova was a reportable business segment. The major classes of assets and liabilities and their carrying amounts immediately prior to the completion of the sales transaction were as follows:
		30-Jun-14
	Assets:
	Current Assets:
	Cash and cash equivalents	$	95,932
	Accounts and notes receivable-less allowances of $410	32,070
	Investments and funds held for clients	114,598
	Income taxes receivable	2,548
	Other current assets	8,908
	Total current assets	254,056
	Other Non-current Assets:
	Goodwill	71,123
	Intangible assets-net of accumulated amortization of $42,266	37,185
	Other property and investments-net	4,656
	Total other non-current assets	112,964
	Total assets	367,020
	Liabilities:
	Current Liabilities:
	Accounts payable	72,453
	Client fund obligations	115,333
	Current portion of long-term debt	67
	Other current liabilities	35,329
	Total current liabilities	223,182
	Long-term borrowings under committed line of credit	40,000
	Other non-current liabilities	2,117
	Total liabilities	$	265,299
	Amounts reported in discontinued operations for 2013 and 2014 relate solely to the Ecova business segment. The following table presents amounts that were included in discontinued operations for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Revenues	$	—		$	46,398		$	87,534		$	133,365
	Gain on sale of Ecova (1)	—			—			161,100			—
	Transaction expenses and accelerated employee benefits (2)	86			—			9,062			—
	Gain on sale of Ecova, net of transaction expenses	(86		)	—			152,038			—
	Income (loss) before income taxes	(86		)	5,540			156,513			10,999
	Income tax expense (benefit)	(31		)	2,092			85,741			4,178
	Net income (loss) from discontinued operations	(55		)	3,448			70,772			6,821
	Net income attributable to noncontrolling interests	—			(485		)	(187		)	(1,292		)
Net income (loss) from discontinued operations attributable to Avista Corp. shareholders	$	(55	)	$	2,963		$	70,585		$	5,529
-1	This represents the gross gain recorded to discontinued operations. The gain net of taxes and transactions expenses is $68.0 million.
-2	This represents Avista Corp.'s portion of the total transaction expenses. All transaction expenses paid on the Ecova sale were $11.0 million, of which $5.4 million were withheld from the net proceeds and the remainder were paid during the second and third quarter of 2014. The transaction expenses were for legal, accounting and other consulting fees and the accelerated employee benefits related to employee stock options which were settled in accordance with the Ecova equity plan.

Derivatives_And_Risk_Managemen

Derivatives And Risk Management	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedges, Assets [Abstract]	'
Derivatives And Risk Management	'
	DERIVATIVES AND RISK MANAGEMENT
	The below disclosures in Note 6 apply only to Avista Utilities; AERC and its primary subsidiary AEL&P do not enter into derivative instruments.
	Energy Commodity Derivatives
	Avista Utilities 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 Utilities utilizes derivative instruments, such as forwards, futures, swaps and options in order to manage the various risks relating to these commodity price exposures. The Company has an energy resources risk policy and control procedures to manage these risks. The Company’s Risk Management Committee establishes the Company’s energy resources risk policy and monitors compliance. The Risk Management Committee is comprised of certain Company officers and other members of management. The Audit Committee of the Company’s Board of Directors periodically reviews and discusses enterprise risk management processes, and it focuses on the Company’s material financial and accounting risk exposures and the steps management has undertaken to control them.
	As part of the Company's resource procurement and management operations in the electric business, the Company engages in an ongoing process of resource optimization, which involves the economic selection from available energy resources to serve the Company's load obligations and the use of these resources to capture available economic value. The Company transacts in wholesale markets by selling and purchasing 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 the related financial risks. These transactions range from terms of intra-hour up to multiple years.
	Avista Utilities makes continuing projections of:
	•	electric loads at various points in time (ranging from intra-hour to multiple years) based on, among other things, estimates of customer usage and weather, historical data and contract terms, and
	•	resource availability at these points in time based on, among other things, fuel choices and fuel markets, estimates of streamflows, availability of generating units, historic and forward market information, contract terms, and experience.
	On the basis of these projections, the Company makes purchases and sales of electric capacity and energy, fuel for electric generation, and related derivative instruments to match expected resources to expected electric load requirements and reduce exposure to electricity (or fuel) market price changes. Resource optimization involves generating plant dispatch and scheduling available resources and also includes transactions such as:
	•	purchasing fuel for generation,
	•	when economical, selling fuel and substituting wholesale electric purchases, and
	•	other wholesale transactions to capture the value of generation and transmission resources and fuel delivery capacity contracts.
	Avista Utilities’ optimization process includes entering into hedging transactions to manage risks. Transactions include both physical energy contracts and related derivative financial instruments.
	As part of its resource procurement and management of its natural gas business, Avista Utilities 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 Utilities’ distribution system. However, daily variations in natural gas demand can be significantly different than monthly demand projections. On the basis of these projections, Avista Utilities plans and executes a series of transactions to hedge a significant 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 Utilities also leaves a significant portion of its natural gas supply requirements unhedged for purchase in short-term and spot markets.
	Natural gas resource optimization activities include:
	•	wholesale market sales of surplus natural gas supplies,
	•	optimization of interstate pipeline transportation capacity not needed to serve daily load, and
	•	purchases and sales of natural gas to optimize use of storage capacity.
	The following table presents the underlying energy commodity derivative volumes as of September 30, 2014 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)
		MWH		MWH			mmBTUs			mmBTUs		MWH	MWH			mmBTUs	mmBTUs
	2014	237		720			12,660			39,325		138	885			1,496	24,288
	2015	508		2,436			13,413			115,860		254	2,935			1,490	89,925
	2016	397		948			2,505			63,173		287	1,634			910	52,713
	2017	397		—			675			2,895		286	—			—	2,895
	2018	397		—			—			—		286	—			—	—
	Thereafter	235		—			—			—		158	—			—	—
	-1	Physical transactions represent commodity transactions where Avista Utilities will take delivery of either electricity or natural gas and financial transactions represent derivative instruments with no physical delivery, such as futures, swaps or options.
	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 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 Contracts
	A significant portion of Avista Utilities’ 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 Utilities’ short-term natural gas transactions and long-term Canadian transportation contracts are committed based on Canadian currency prices and settled within sixty days with U.S. dollars. Avista Utilities hedges a portion of the foreign currency risk by purchasing Canadian currency contracts when such commodity transactions are initiated. This risk has not had a material effect on the Company’s financial condition, results of operations or cash flows and these differences in cost related to currency fluctuations were included with natural gas supply costs for ratemaking.
	The following table summarizes the foreign currency hedges that the Company has entered into as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,			December 31,
		2014			2013
	Number of contracts	23			23
	Notional amount (in United States dollars)	$	15,734		$	8,631
	Notional amount (in Canadian dollars)	17,326			9,191
	Interest Rate Swap Agreements
	Avista Corp. is affected by fluctuating interest rates related to a portion of its existing debt, and future borrowing requirements. The Finance Committee of the Board of Directors periodically reviews and discusses interest rate risk management processes, and it focuses on the steps management has undertaken to manage it. The Risk Management Committee also reviews the interest risk management plan. Avista Corp. has established a policy to limit its variable rate exposures to a percentage of total capitalization. Additionally, interest rate risk is managed by monitoring market conditions when timing the issuance of long-term debt and optional debt redemptions and through the use of fixed rate long-term debt with varying maturities. The Company hedges a portion of its interest rate risk with financial derivative instruments, which may include interest rate swaps and U.S. Treasury lock agreements. These interest rate swaps 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 interest rate swaps that the Company has entered into as of September 30, 2014 and December 31, 2013 (dollars in thousands):
	Balance Sheet Date		Number of Contracts	Notional Amount				Mandatory Cash Settlement Date
	September 30, 2014		2	$	50,000			2014
			5	75,000				2015
			5	95,000				2016
			3	45,000				2017
			7	155,000				2018
	December 31, 2013		2	50,000				2014
			2	45,000				2015
			2	40,000				2016
			1	15,000				2017
			4	95,000				2018
	In October 2014, the Company cash settled two interest rate swap contracts (notional aggregate amount of $50.0 million) and received a total of $5.4 million. The interest rate swap contracts were settled in connection with the pricing of $60.0 million of Avista Corp. first mortgage bonds that are expected to be issued in December 2014 (see Note 9). Upon settlement of interest rate swaps, the regulatory asset or liability (included as part of long-term debt) is amortized as a component of interest expense over the term of the associated debt.
	In anticipation of issuing long-term debt in 2018, the Company entered into two interest rate swap agreements in October 2014, with a total aggregate notional amount of $50.0 million and a mandatory cash settlement date of June 2018. Including the October 2014 interest rate swap agreements, the Company has a total of nine interest rate swap agreements with an aggregate notional amount of $205.0 million related to the anticipated long-term debt issuance in 2018.
	Derivative Instruments Summary
	The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of September 30, 2014 (in thousands):
				Fair Value
	Derivative		Balance Sheet Location	Gross				Gross			Collateral		Net Asset
				Asset				Liability			Netting		(Liability)
													in Balance
													Sheet
	Foreign currency contracts		Other current liabilities	$	—			$	(280	)	$	—	$	(280	)
Interest rate contracts		Other current assets	7,106				—			—		7,106
Interest rate contracts		Other property and investments - net	4,933				(3,786		)	—		1,147
Interest rate contracts		Other non-current liabilities and deferred credits	1,261				(30,699		)	12,730		(16,708		)
Commodity contracts (1)		Current utility energy commodity derivative assets	11,371				(8,037		)	—		3,334
Commodity contracts (1)		Non-current utility energy commodity derivative assets	10,639				(8,946		)	—		1,693
Commodity contracts (1)		Current utility energy commodity derivative liabilities	21,002				(26,060		)	49		(5,009		)
Commodity contracts (1)		Other non-current liabilities and deferred credits	10,537				(25,383		)	886		(13,960		)
Total derivative instruments recorded on the balance sheet			$	66,849			$	(103,191	)	$	13,665	$	(22,677	)
The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2013 (in thousands):
			Fair Value
Derivative		Balance Sheet Location	Gross				Gross			Collateral		Net Asset
			Asset				Liability			Netting		(Liability)
												in Balance
												Sheet
Foreign currency contracts		Other current assets	$	7			$	(6	)	$	—	$	1
Interest rate contracts		Other current assets	13,968				—			—		13,968
Interest rate contracts		Other property and investments - net	19,575				—			—		19,575
Commodity contracts (1)		Current utility energy commodity derivative assets	7,416				(4,394		)	—		3,022
Commodity contracts (1)		Non-current utility energy commodity derivative assets	7,610				(6,756		)	—		854
Commodity contracts (1)		Current utility energy commodity derivative liabilities	23,455				(37,306		)	2,976		(10,875		)
Commodity contracts (1)		Other non-current liabilities and deferred credits	17,101				(41,213		)	5,756		(18,356		)
Total derivative instruments recorded on the balance sheet			$	89,132			$	(89,675	)	$	8,732	$	8,189
-1	Avista Corp. had a master netting agreement that governed the transactions of multiple affiliated legal entities under this single master netting agreement. This master netting agreement allowed for cross-commodity netting (i.e. netting physical power, physical natural gas, and financial transactions) and cross-affiliate netting for the parties to the agreement. Avista Corp. performed cross-commodity netting for each legal entity that is a party to the master netting agreement for presentation in the Condensed Consolidated Balance Sheets; however, Avista Corp. did not perform cross-affiliate netting because the Company believed that cross-affiliate netting may not be enforceable. Therefore, the requirements for cross-affiliate netting under ASC 210-20-45 were not applicable for Avista Corp. As of December 31, 2013, all derivatives for each affiliated entity under this master netting agreement were in a net liability position. As such, there was no additional netting which required disclosure for that period. In May 2014, this master netting agreement was terminated and each affiliated legal entity is now under their own separate agreement. As of September 30, 2014, the Company no longer has any agreements where cross-affiliate netting is allowed under the agreement, but not performed by the Company.
Exposure to Demands for Collateral
The Company'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 the Company's credit ratings or changes in market prices. In periods of price volatility, the level of exposure can change significantly. As a result, sudden and significant demands may be made against the Company's credit facilities and cash. The Company actively monitors the exposure to possible collateral calls and takes steps to mitigate capital requirements. As of September 30, 2014, the Company had deposited cash in the amount of $7.4 million and letters of credit of $38.5 million as collateral for certain energy derivative contracts. The Company also had deposited cash in the amount of $12.7 million as collateral for its interest rate swap derivative contracts. The Condensed Consolidated Balance Sheet at September 30, 2014 reflects the offsetting of $13.7 million of cash collateral against net derivative positions where a legal right of offset exists. As of December 31, 2013, the Company had deposited cash in the amount of $26.1 million and letters of credit of $20.3 million as collateral for certain energy derivative contracts. As of September 30, 2014 and December 31, 2013, the Company did not hold any cash as collateral from counterparties for energy derivative contracts. The Consolidated Balance Sheet at December 31, 2013 reflects the offsetting of $8.7 million of cash collateral against net derivative positions where a legal right of offset exists.
Certain of the Company’s derivative instruments contain provisions that require the Company to maintain an "investment grade" credit rating from the major credit rating agencies. If the Company’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 aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position as of September 30, 2014 was $4.3 million. If the credit-risk-related contingent features underlying these agreements were triggered on September 30, 2014, the Company could be required to post $5.9 million of additional collateral to its counterparties. The aggregate fair value of all derivative instruments with credit-risk-related contingent features that were in a liability position as of December 31, 2013 was $13.3 million. If the credit-risk-related contingent features underlying these agreements had been triggered on December 31, 2013, the Company could have been required to post $12.6 million of additional collateral to its counterparties.
Credit Risk
Credit risk relates to the potential losses that the Company would incur as a result of non-performance by counterparties of their contractual obligations to deliver energy or make financial settlements. The Company often extends credit to counterparties and customers and is exposed to the risk that it may not be able to collect amounts owed to the Company. Credit risk includes potential counterparty default due to circumstances:
•	relating directly to it,
•	caused by market price changes, and
•	relating to other market participants that have a direct or indirect relationship with such counterparty.
Changes in market prices may dramatically alter the size of credit risk with counterparties, even when conservative credit limits are established. Should a counterparty fail to perform, the Company may be required to honor the underlying commitment or to replace existing contracts with contracts at then-current market prices.
The Company enters into bilateral transactions with various counterparties. The Company also trades energy and related derivative instruments through clearinghouse exchanges.
The Company seeks to mitigate bilateral credit risk by:
•	entering into bilateral contracts that specify credit terms and protections against default,
•	applying credit limits and duration criteria to existing and prospective counterparties,
•	actively monitoring current credit exposures,
•	asserting our collateral rights with counterparties,
•	carrying out transaction settlements timely and effectively, and
•	conducting transactions on exchanges with fully collateralized clearing arrangements that significantly reduce counterparty default risk.
The Company's credit policy includes an evaluation of the financial condition of counterparties. Credit risk management includes collateral requirements or other credit enhancements, such as letters of credit or parent company guarantees. The Company enters into various agreements that address credit risks including standardized agreements that allow for the netting or offsetting of positive and negative exposures.
The Company has concentrations of suppliers and customers in the electric and natural gas industries including:
•	electric and natural gas utilities,
•	electric generators and transmission providers,
•	natural gas producers and pipelines,
•	financial institutions including commodity clearing exchanges and related parties, and
•	energy marketing and trading companies.
In addition, the Company has concentrations of credit risk related to geographic location as it operates in the western United States and western Canada. These concentrations of counterparties and concentrations of geographic location may impact the Company’s overall exposure to credit risk because the counterparties may be similarly affected by changes in conditions.
The Company maintains credit support agreements with certain counterparties and margin calls are periodically made and/or received. Margin calls are triggered when exposures exceed contractual limits or when there are changes in a counterparty’s creditworthiness. Price movements in electricity and natural gas can generate exposure levels in excess of these contractual limits. Negotiating for collateral in the form of cash, letters of credit, or performance guarantees is common industry practice.

Pension_Plans_And_Other_Postre

Pension Plans And Other Postretirement Benefit Plans	9 Months Ended
	Sep. 30, 2014
General Discussion of Pension and Other Postretirement Benefits [Abstract]	'
Pension Plans and Other Postretirement Benefit Plans	'
	PENSION PLANS AND OTHER POSTRETIREMENT BENEFIT PLANS
	The pension and other postretirement benefit plans described below only relate to Avista Utilities and AEL&P. Most other subsidiary employees have salary deferral 401(k) savings plans that are defined contribution plans and these have historically not been significant to the Company.
	Avista Utilities
	The Company has a defined benefit pension plan covering substantially all regular full-time employees at Avista Utilities. Individual benefits under this plan are based upon the employee’s years of service, date of hire and average compensation as specified in the plan. 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 $32.0 million in cash to the pension plan for the nine months ended September 30, 2014 and does not expect to contribute anything further in 2014. The Company contributed $44.3 million in cash to the pension plan in 2013.
	In October 2013, the Company revised its defined benefit pension plan such that as of January 1, 2014 the plan is closed to non-union employees hired or rehired by the Company on or after January 1, 2014. Actively employed non-union employees that were hired prior to January 1, 2014 and who were at that date covered under the defined benefit pension plan will continue accruing benefits as originally specified in the plan. A new and separate defined contribution 401(k) plan replaced the defined benefit pension plan for all non-union employees hired or rehired on or after January 1, 2014. Under the new defined contribution plan, the Company provides a non-elective contribution as a percentage of each employee's pay based on his or her age. This new defined contribution plan is in addition to the existing 401(k) plan in which the Company matches a portion of the pay deferred by each participant. In addition to the changes above, the Company revised the lump sum calculation for non-union participants who retire under the defined benefit pension plan on or after January 1, 2014 to provide retiring employees the election of a lump sum amount equivalent to the present value of the benefits based upon applicable discount rates. In April 2014, the local union in Oregon for the International Brotherhood of Electrical Workers (IBEW) accepted the above plan changes in the latest collective bargaining agreement, and the plan changes are effective for Oregon union workers hired or rehired on or after April 1, 2014.
	The Company also has a Supplemental Executive Retirement Plan (SERP) that provides additional pension benefits to executive officers of the Company. The SERP is intended to provide benefits to executive officers whose benefits under the pension plan are reduced due to the application of Code Section 415 and the deferral of salary under deferred compensation plans. The liability and expense for this plan are included as pension benefits in the tables included in this Note.
	The Company provides certain health care and life insurance benefits for eligible retired employees. The Company accrues the estimated cost of postretirement benefit obligations during the years that employees provide services. In October 2013, the Company revised the health care benefit plan such that beginning on January 1, 2020, the methods for calculating health insurance premiums for non-union retirees under age 65 and active Company employees were revised to establish separate health insurance premiums for each group. In addition, for non-union employees hired or rehired on or after January 1, 2014, upon retirement the Company will provide access to its retiree medical plan, but will no longer contribute towards their medical premiums and each employee would pay the full cost of premiums upon retirement. In April 2014, the local union in Oregon for the IBEW accepted the above plan changes in the latest collective bargaining agreement, and the plan changes are effective for Oregon union workers hired or rehired on or after April 1, 2014.
	The Company has a Health Reimbursement Arrangement to provide employees with tax-advantaged funds to pay for allowable medical expenses upon retirement. The amount earned by the employee is fixed on the retirement date based on the employee’s years of service and the ending salary. The liability and expense of this plan are included as other postretirement benefits.
	The Company provides death benefits to beneficiaries of executive officers who die during their term of office or after retirement. Under the plan, an executive officer’s designated beneficiary will receive a payment equal to twice the executive officer’s annual base salary at the time of death (or if death occurs after retirement, a payment equal to twice the executive officer’s total annual pension benefit). The liability and expense for this plan are included as other postretirement benefits.
	The Company uses a December 31 measurement date for its pension and other postretirement benefit plans. The following table sets forth the components of net periodic benefit costs for the three and nine months ended September 30 (dollars in thousands):
		Pension Benefits						Other Post-retirement Benefits
		2014			2013			2014			2013
	Three months ended September 30:
	Service cost	$	3,868		$	4,743		$	499		$	971
	Interest cost	6,706			5,978			1,353			1,373
	Expected return on plan assets	(8,110		)	(6,900		)	(472		)	(402		)
	Amortization of prior service cost	6			75			(43		)	(37		)
	Net loss recognition	1,163			3,220			826			1,395
	Net periodic benefit cost	$	3,633		$	7,116		$	2,163		$	3,300
	Nine months ended September 30:
	Service cost	$	12,754		$	14,229		$	1,972		$	3,035
	Interest cost	20,118			17,934			4,059			4,153
	Expected return on plan assets	(24,330		)	(20,700		)	(1,416		)	(1,202		)
	Amortization of prior service cost	18			225			(129		)	(111		)
	Net loss recognition	2,334			9,989			2,001			4,342
	Net periodic benefit cost	$	10,894		$	21,677		$	6,487		$	10,217
	AEL&P
	Union Employees
	Pension benefits for all union employees of AEL&P are provided through the Alaska Electrical Pension Fund Retirement Plan, a multiemployer plan to which AEL&P pays a defined contribution amount per union employee pursuant to a collective bargaining agreement with the IBEW.
	AEL&P also participates in a multiemployer plan that provides substantially all union workers with health care and other welfare benefits during their working lives and after retirement. AEL&P pays a defined contribution amount per union employee pursuant to a collective bargaining agreement with the IBEW.
	Non-Union Employees
	AEL&P has a defined contribution money purchase pension plan covering all employees of AEL&P that are not covered by a collective bargaining agreement. Contributions to the plan are made based on a percentage of each employee's compensation.
	AEL&P also has a noncontributory 401(k) savings plan, which covers substantially all nonunion employees who have completed 1,000 hours of service during a 12-month period. Employees who elect to participate may contribute up to the Internal Revenue Service's maximum amount.
	The pension and other postretirement plans described above for AEL&P are not significant to Avista Corp.

Committed_Lines_of_Credit

Committed Lines of Credit	9 Months Ended
	Sep. 30, 2014
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. In April 2014, the Company amended this committed line of credit agreement to extend the expiration date to April 2019. The amendment also provides the Company the option to request an extension for an additional one or two years beyond April 2019, provided, 1) there are no default events prior to the requested extension, and 2) the remaining term of agreement, including the requested extension period, does not exceed five years. The amendment did not change the amount of the committed line of credit.
	The committed line of credit is secured by non-transferable First Mortgage Bonds of the Company issued to the agent bank that would only become due and payable in the event, and then only to the extent, that the Company defaults on its obligations under the committed line of credit.
	The committed line of credit agreement contains customary covenants and default provisions. The credit agreement has a covenant which does not permit the ratio of “consolidated total debt” to “consolidated total capitalization” of Avista Corp. to be greater than 65 percent at any time. As of September 30, 2014, the Company was in compliance with this covenant.
	Balances outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed lines of credit were as follows as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,			December 31,
		2014			2013
	Borrowings outstanding at end of period	$	35,000		$	171,000
	Letters of credit outstanding at end of period	$	45,614		$	27,434
	Average interest rate on borrowings at end of period	0.92		%	1.02		%
	As of September 30, 2014 the borrowings outstanding under Avista Corp.'s committed line of credit were classified as short-term borrowings on the Condensed Consolidated Balance Sheet.
	AEL&P
	AEL&P has a committed line of credit in the amount of $14.5 million with an expiration date of June 2015. As of September 30, 2014, there were no borrowings outstanding under this committed line of credit. Under the terms of the agreement, interest on outstanding borrowings accrues at 0.25 percent below the prime rate with a floor of 4 percent. In addition, a fee of 0.45 percent accrues on the unadvanced portion of the line of credit.
	Ecova
	Ecova had a $125.0 million committed line of credit agreement with various financial institutions that had an expiration date of July 2017. The credit agreement was secured by all of Ecova's assets excluding investments and funds held for clients. Since Ecova was disposed of as of June 30, 2014, the balance of this credit agreement is no longer on the balance sheet as of September 30, 2014.
	The balance outstanding and interest rate of borrowings under Ecova’s credit agreement were as follows as of December 31, 2013 (dollars in thousands):
		December 31,
		2013
	Borrowings outstanding at end of period	$	46,000
	Average interest rate on borrowings at end of period	2.17		%
	As of December 31, 2013 the borrowings outstanding under Ecova's committed line of credit were classified as long-term borrowings under committed line of credit on the Condensed Consolidated Balance Sheet.

LongTerm_Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2014
Long-term Debt, Unclassified [Abstract]	'
Long-Term Debt	'
	LONG-TERM DEBT
	The following details long-term debt outstanding as of September 30, 2014 and December 31, 2013 (dollars in thousands):
	Maturity			Interest		September 30,				December 31,
	Year		Description	Rate		2014				2013
	Avista Corp. Secured Long-Term Debt
	2016		First Mortgage Bonds	0.84%		$	90,000			$	90,000
	2018		First Mortgage Bonds	5.95%		250,000				250,000
	2018		Secured Medium-Term Notes	7.39%-7.45%		22,500				22,500
	2019		First Mortgage Bonds	5.45%		90,000				90,000
	2020		First Mortgage Bonds	3.89%		52,000				52,000
	2022		First Mortgage Bonds	5.13%		250,000				250,000
	2023		Secured Medium-Term Notes	7.18%-7.54%		13,500				13,500
	2028		Secured Medium-Term Notes	6.37%		25,000				25,000
	2032		Secured Pollution Control Bonds (1)	-1		66,700				66,700
	2034		Secured Pollution Control Bonds (1)	-1		17,000				17,000
	2035		First Mortgage Bonds	6.25%		150,000				150,000
	2037		First Mortgage Bonds	5.70%		150,000				150,000
	2040		First Mortgage Bonds	5.55%		35,000				35,000
	2041		First Mortgage Bonds	4.45%		85,000				85,000
	2047		First Mortgage Bonds	4.23%		80,000				80,000
			Total Avista Corp. secured long-term debt			1,376,700				1,376,700
	Alaska Electric Light and Power Company Secured Long-Term Debt
	2044		First Mortgage Bonds (2)	4.54%		75,000				—
			Total consolidated secured long-term debt			1,451,700				1,376,700
			Other long-term debt and capital leases			74,754				4,630
			Settled interest rate swaps (3)			(23,118		)		(23,560		)
			Unamortized debt discount			(954		)		(1,287		)
			Total			1,502,382				1,356,483
			Secured Pollution Control Bonds held by Avista Corporation (1)			(83,700		)		(83,700		)
			Current portion of long-term debt and capital leases			(6,471		)		(358		)
			Total long-term debt and capital leases			$	1,412,211			$	1,272,425
	-1	In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Condensed Consolidated Balance Sheets.
	-2	In September 2014, AEL&P issued $75.0 million of 4.54 percent first mortgage bonds due in 2044 to two institutional investors in the private placement market. The first mortgage bonds were issued under and in accordance with the AEL&P Mortgage and Deed of Trust, dated as of July 1, 2014.
	-3	Upon settlement of interest rate swaps, these are recorded as a regulatory asset or liability and included as part of long-term debt above. They are amortized as a component of interest expense over the life of the associated debt and included as a part of the Company's cost of debt calculation for ratemaking purposes.
	In October 2014, the Company entered into a bond purchase agreement with three institutional investors in the private placement market for the issuance and sale of $60.0 million of Avista Corp. first mortgage bonds that are expected to be issued in December 2014. The first mortgage bonds will bear an interest rate of 4.11 percent and mature in December 2044. In connection with this pricing, the Company cash settled two interest rate swap contracts (notional aggregate amount of $50.0 million) and received a total of $5.4 million. Upon settlement of interest rate swaps, the regulatory asset or liability (included as part of long-term debt) is amortized as a component of interest expense over the term of the associated debt.
	Snettisham Capital Lease Obligation
	Included in long-term capital leases above is a power purchase agreement between AEL&P and AIDEA, an agency of the State of Alaska, under which AEL&P has a take-or-pay obligation, expiring in December 2038, to purchase all the output of the 78 MW Snettisham hydroelectric project. AIDEA issued $100.0 million in revenue bonds to finance its acquisition of the project and the payments by AEL&P are designed to be more than sufficient to enable the AIDEA to pay the principal and interest amount of its revenue bonds, bearing interest at rates ranging from 4.9 percent to 6.0 percent and maturing in January 2034. AEL&P will make its last bond payment to AIDEA in December 2033. The payments by AEL&P under the agreement are unconditional, notwithstanding any suspension, reduction or curtailment of the operation of the project. The bonds are payable solely out of AIDEA's receipts under the agreement. AEL&P is also obligated to operate, maintain and insure the project. AEL&P's payments for power under the agreement are approximately $10.6 million per year, while debt service on the bonds is approximately $5.9 million per year, which are included in the $10.6 million total costs of power. For accounting purposes, this power purchase agreement is treated as a capital lease.
	Snettisham Electric Company, a non-operating subsidiary of AERC, has the option to purchase the Snettisham project at any time for the principal amount of the bonds outstanding at that time.
	While the power purchase agreement is treated as a capital lease for accounting purposes, for ratemaking purposes, this agreement is treated as an operating lease with a constant level of annual rental expense (straight line expense). Because of this regulatory treatment, any difference between the operating lease expense for ratemaking purposes and the expenses recognized under capital lease treatment (interest and depreciation of the capital lease asset) will be recorded as a regulatory asset and amortized during the later years of the lease when the capital lease expense is less than the operating lease expense included in base rates.
	The Company evaluated this agreement to determine if it has a variable interest which must be consolidated. Based on this evaluation, AIDEA will not be consolidated under ASC 810 "Consolidation" because AIDEA is a government agency and ASC 810 has a specific scope exception which does not allow for the consolidation of government organizations.
	As of September 30, 2014, the capital lease obligation was $70.5 million and the capital lease asset was $71.0 million (included in utility plant in service on the Condensed Consolidated Balance Sheet) and accumulated amortization was $0.9 million. For the three months ended September 30, 2014 interest on the capital lease obligation was $1.0 million and amortization of the capital lease asset was $0.9 million. These amounts were included in utility resource costs in the Condensed Consolidated Statements of Income.
	The following table details future capital lease obligations, including interest, under the Snettisham PPA (dollars in thousands):
		2014			2015				2016				2017		2018		Thereafter		Total
	Principal	$	526		$	2,230			$	2,350			$	2,480	$	2,615	$	60,280	$	70,481
	Interest	954			3,690				3,567				3,438		3,305		28,529		43,483
	Total	$	1,480		$	5,920			$	5,917			$	5,918	$	5,920	$	88,809	$	113,964
	Nonrecourse Long-Term Debt
	Nonrecourse long-term debt (including current portion) represents the long-term debt of Spokane Energy. To provide funding to acquire a long-term fixed rate electric capacity contract from Avista Corp., Spokane Energy borrowed $145.0 million from a funding trust in December 1998. The long-term debt has scheduled monthly installments and interest at a fixed rate of 8.45 percent with the final payment due in January 2015. Spokane Energy bears full recourse risk for the debt, which is secured by the fixed rate electric capacity contract and $1.6 million of funds held in a trust account. As of September 30, 2014, the entire remaining portion of the nonrecourse debt has been included in current liabilities due to its maturity in January 2015.

Fair_Value

Fair Value	9 Months Ended
	Sep. 30, 2014
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), nonrecourse long-term debt 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 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, 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 September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30, 2014								December 31, 2013
		Carrying				Estimated				Carrying			Estimated
		Value				Fair Value				Value			Fair Value
	Long-term debt (Level 2)	$	951,000			$	1,100,345			$	951,000		$	1,054,512
	Long-term debt (Level 3)	417,000				431,758				342,000			329,581
	Snettisham capital lease obligation (Level 3)	70,481				77,835				—			—
	Nonrecourse long-term debt (Level 3)	5,666				5,756				17,838			18,636
	Long-term debt to affiliated trusts (Level 3)	51,547				38,583				51,547			37,114
	These estimates of fair value of long-term debt and long-term debt to affiliated trusts were primarily based on available market information. Due to the unique nature of the long-term fixed rate electric capacity contract securing the long-term debt of Spokane Energy (nonrecourse long-term debt) and 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 following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Condensed Consolidated Balance Sheets as of September 30, 2014 and December 31, 2013 at fair value on a recurring basis (dollars in thousands):
		Level 1				Level 2				Level 3			Counterparty			Total
													and Cash
													Collateral
													Netting (1)
	30-Sep-14
	Assets:
	Energy commodity derivatives	$	—			$	52,691			$	—		$	(47,664	)	$	5,027
	Level 3 energy commodity derivatives:
	Natural gas exchange agreement	—				—				58			(58		)	—
	Power exchange agreement	—				—				800			(800		)	—
	Interest rate swaps	—				13,300				—			(5,047		)	8,253
	Funds held in trust account of Spokane Energy	1,600				—				—			—			1,600
	Deferred compensation assets:
	Fixed income securities (2)	1,831				—				—			—			1,831
	Equity securities (2)	6,096				—				—			—			6,096
	Total	$	9,527			$	65,991			$	858		$	(53,569	)	$	22,807
	Liabilities:
	Energy commodity derivatives	$	—			$	52,881			$	—		$	(48,599	)	$	4,282
	Level 3 energy commodity derivatives:
	Natural gas exchange agreement	—				—				1,529			(58		)	1,471
	Power exchange agreement	—				—				13,654			(800		)	12,854
	Power option agreement	—				—				362			—			362
	Foreign currency derivatives	—				280				—			—			280
	Interest rate swaps	—				34,485				—			(17,777		)	16,708
	Total	$	—			$	87,646			$	15,545		$	(67,234	)	$	35,957
		Level 1				Level 2				Level 3			Counterparty			Total
													and Cash
													Collateral
													Netting (1)
	31-Dec-13
	Assets:
	Energy commodity derivatives	$	—			$	55,243			$	—		$	(51,367	)	$	3,876
	Level 3 energy commodity derivatives:
	Power exchange agreement	—				—				339			(339		)	—
	Foreign currency derivatives	—				7				—			(6		)	1
	Interest rate swaps	—				33,543				—			—			33,543
	Investments and funds held for clients:
	Money market funds	11,180				—				—			—			11,180
	Securities available for sale:
	U.S. government agency	—				61,078				—			—			61,078
	Municipal	—				3,518				—			—			3,518
	Corporate fixed income – financial	—				3,000				—			—			3,000
	Corporate fixed income – industrial	—				765				—			—			765
	Certificate of deposits	—				1,000				—			—			1,000
Funds held in trust account of Spokane Energy	1,600				—				—			—			1,600
Deferred compensation assets:
Fixed income securities (2)	1,960				—				—			—			1,960
Equity securities (2)	6,470				—				—			—			6,470
Total	$	21,210			$	158,154			$	339		$	(51,712	)	$	127,991
Liabilities:
Energy commodity derivatives	$	—			$	72,895			$	—		$	(60,099	)	$	12,796
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—				—				1,219			—			1,219
Power exchange agreement	—				—				14,780			(339		)	14,441
Power option agreement	—				—				775			—			775
Foreign currency derivatives	—				6				—			(6		)	—
Total	$	—			$	72,901			$	16,774		$	(60,444	)	$	29,231
-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 trading securities and are included in other property and investments-net on the Condensed Consolidated Balance Sheets.
Avista Corp. enters into forward contracts to purchase or sell a specified amount of energy at a specified time, or during a specified period, in the future. These contracts are entered into as part of Avista Corp.’s management of loads and resources and certain contracts are considered derivative instruments. The difference between the amount of derivative assets and liabilities disclosed in respective levels and the amount of derivative assets and liabilities disclosed on the Condensed Consolidated Balance Sheets is due to netting arrangements with certain counterparties. The Company uses quoted market prices and forward price curves to estimate the fair value of utility derivative commodity instruments included in Level 2. In particular, electric derivative valuations are performed using broker quotes, adjusted for periods in between quotable periods. Natural gas derivative valuations are estimated using New York Mercantile Exchange (NYMEX) pricing for similar instruments, adjusted for basin differences, using broker quotes. Where observable inputs are available for substantially the full term of the contract, the derivative asset or liability is included in Level 2.
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 $1.0 million as of September 30, 2014 and $0.7 million as of December 31, 2013.
Level 3 Fair Value
For the power exchange agreement, the Company compares the Level 2 brokered quotes and forward price curves described above to an internally developed forward price which is based on the average operating and maintenance (O&M) charges from four surrogate nuclear power plants around the country for the current year. Because the nuclear power plant O&M charges are only known for one year, all forward years are estimated assuming an annual escalation. In addition to the forward price being estimated using unobservable inputs, the Company also estimates the volumes of the transactions that will 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. Generally, a change in the current year O&M charges for the surrogate plants is accompanied by a directionally similar change in O&M charges in future years. There is generally not a correlation between external market prices and the O&M charges used to develop the internal forward price.
For the power commodity option agreement, the Company uses the Black-Scholes-Merton valuation model to estimate the fair value, and this model includes significant inputs not observable or corroborated in the market. These inputs include 1) the strike price (which is an internally derived price based on a combination of generation plant heat rate factors, natural gas market pricing, delivery and other O&M charges), 2) estimated delivery volumes, and 3) volatility rates for periods beyond October 2017. Significant increases or decreases in any of these inputs in isolation would result in a significantly higher or lower fair value measurement. Generally, changes in overall commodity market prices and volatility rates are accompanied by directionally similar changes in the strike price and volatility assumptions used in the calculation.
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 September 30, 2014 (dollars in thousands):
		Fair Value (Net) at
		September 30, 2014				Valuation Technique		Unobservable		Range
								Input
Power exchange agreement		$	(12,854	)		Surrogate facility		O&M charges		$30.66-$55.56/MWh (1)
						pricing		Escalation factor		3% - 2014 to 2019
								Transaction volumes		310,103 - 397,116 MWhs
Power option agreement		(362		)		Black-Scholes-		Strike price		$56.20/MWh - 2015
						Merton				$67.81/MWh - 2019
								Delivery volumes		32,472 - 287,147 MWhs
								Volatility rates		0.20 (2)
Natural gas exchange		(1,471		)		Internally derived		Forward purchase		$3.43 - $3.68/mmBTU
agreement						weighted average		prices
						cost of gas		Forward sales prices		$4.19 - $4.72/mmBTU
								Purchase volumes		280,000 - 310,000 mmBTUs
								Sales volumes		279,990 - 310,000 mmBTUs
(1) The average O&M charges for the delivery year beginning in November 2014 were $42.90 per MWh. For ratemaking purposes the average O&M charges to be included for recovery in retail rates vary slightly between regulatory jurisdictions. The average O&M charges for the delivery year beginning in 2014 were $43.11 for Washington and $42.90 for Idaho.
(2) The estimated volatility rate of 0.20 is compared to actual quoted volatility rates of 0.30 for 2014 to 0.19 in October 2017.
Avista Corp.'s Risk Management team and accounting team are responsible for developing the valuation methods described above and both groups report to the Chief Financial Officer. The valuation methods, significant inputs and resulting fair values described above are reviewed on at least a quarterly basis by the risk management team and the accounting team 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 nine months ended September 30 (dollars in thousands):
	Natural Gas Exchange Agreement				Power Exchange Agreement				Power Option Agreement			Total
Three months ended September 30, 2014:
Balance as of July 1, 2014	$	(2,183	)		$	(7,919	)		$	(605	)	$	(10,707	)
Total gains or losses (realized/unrealized):
Included in net income	—				—				—			—
Included in other comprehensive income	—				—				—			—
Included in regulatory assets/liabilities (1)	712				(4,935		)		243			(3,980		)
Purchases	—				—				—			—
Issuance	—				—				—			—
Settlements	—				—				—			—
Transfers to/from other categories	—				—				—			—
Ending balance as of September 30, 2014	$	(1,471	)		$	(12,854	)		$	(362	)	$	(14,687	)
Three months ended September 30, 2013:
Balance as of July 1, 2013	$	(1,022	)		$	(22,179	)		$	(596	)	$	(23,797	)
Total gains or losses (realized/unrealized):
Included in net income	—				—				—			—
Included in other comprehensive income	—				—				—			—
Included in regulatory assets/liabilities (1)	(170		)		6,135				(165		)	5,800
Purchases	—				—				—			—
Issuance	—				—				—			—
Settlements	(1		)		—				—			(1		)
Transfers to/from other categories	—				—				—			—
Ending balance as of September 30, 2013	$	(1,193	)		$	(16,044	)		$	(761	)	$	(17,998	)
Nine months ended September 30, 2014:
Balance as of January 1, 2014	$	(1,219	)		$	(14,441	)		$	(775	)	$	(16,435	)
Total gains or losses (realized/unrealized):
Included in net income	—				—				—			—
Included in other comprehensive income	—				—				—			—
Included in regulatory assets/liabilities (1)	2,796				2,120				413			5,329
Purchases	—				—				—			—
Issuance	—				—				—			—
Settlements	(3,048		)		(533		)		—			(3,581		)
Transfers to/from other categories	—				—				—			—
Ending balance as of September 30, 2014	$	(1,471	)		$	(12,854	)		$	(362	)	$	(14,687	)
	Natural Gas Exchange Agreement				Power Exchange Agreement				Power Option Agreement			Total
Nine months ended September 30, 2013:
Balance as of January 1, 2013	$	(2,379	)		$	(18,692	)		$	(1,480	)	$	(22,551	)
Total gains or losses (realized/unrealized):
Included in net income	—				—				—			—
Included in other comprehensive income	—				—				—			—
Included in regulatory assets/liabilities (1)	1,637				(113		)		719			2,243
Purchases	—				—				—			—
Issuance	—				—				—			—
Settlements	(451		)		2,761				—			2,310
Transfers from other categories	—				—				—			—
Ending balance as of September 30, 2013	$	(1,193	)		$	(16,044	)		$	(761	)	$	(17,998	)
-1	The UTC and the IPUC issued accounting orders authorizing Avista Corp. to offset commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment defers the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. The orders provide for Avista Corp. to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the period of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rates cases.

Earnings_Per_Common_Share_Attr

Earnings Per Common Share Attributable To Avista Corporation	9 Months Ended
	Sep. 30, 2014
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 nine months ended September 30 (in thousands, except per share amounts):
		Three months ended						Nine months ended
		September 30,						September 30,
		2014			2013			2014		2013
	Numerator:
	Net income from continuing operations attributable to Avista Corp. shareholders	$	10,506		$	8,450		$	89,236	$	73,882
	Net income (loss) from discontinued operations attributable to Avista Corp. shareholders	(55		)	2,963			70,585		5,529
	Subsidiary earnings adjustment for dilutive securities (discontinued operations)	—			(81		)	5		(163		)
	Adjusted net income (loss) from discontinued operations attributable to Avista Corp. shareholders for computation of diluted earnings per common share	$	(55	)	$	2,882		$	70,590	$	5,366
	Denominator:
	Weighted-average number of common shares outstanding-basic	63,934			59,994			61,413		59,933
	Effect of dilutive securities:
	Performance and restricted stock awards	310			38			212		31
	Weighted-average number of common shares outstanding-diluted	64,244			60,032			61,625		59,964
	Earnings per common share attributable to Avista Corp. shareholders, basic:
	Earnings per common share from continuing operations	$	0.16		$	0.14		$	1.45	$	1.23
	Earnings per common share from discontinued operations	$	—		$	0.05		$	1.15	$	0.09
	Total earnings per common share attributable to Avista Corp. shareholders, basic	$	0.16		$	0.19		$	2.6	$	1.32
	Earnings per common share attributable to Avista Corp. shareholders, diluted:
	Earnings per common share from continuing operations	$	0.16		$	0.14		$	1.45	$	1.23
	Earnings per common share from discontinued operations	$	—		$	0.05		$	1.14	$	0.09
	Total earnings per common share attributable to Avista Corp. shareholders, diluted	$	0.16		$	0.19		$	2.59	$	1.32
	There were no shares excluded from the calculation because they were antidilutive.

Commitments_And_Contingencies

Commitments And Contingencies	9 Months Ended
	Sep. 30, 2014
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.
	Federal Energy Regulatory Commission Inquiry
	In April 2004, the Federal Energy Regulatory Commission (FERC) approved the contested Agreement in Resolution of Section 206 Proceeding (Agreement in Resolution) which stated that there was: (1) no evidence that any executives or employees of Avista Utilities or Avista Energy knowingly engaged in or facilitated any improper trading strategy during 2000 and 2001; (2) no evidence that Avista Utilities or Avista Energy engaged in any efforts to manipulate the western energy markets during 2000 and 2001; and (3) no finding that Avista Utilities or Avista Energy withheld relevant information from the FERC's inquiry into the western energy markets for 2000 and 2001 (Trading Investigation). In May 2004, the FERC provided notice that Avista Energy was no longer subject to an investigation reviewing certain bids above $250 per MW in energy markets operated by the California Independent System Operator (CalISO) and the California Power Exchange (CalPX)(Bidding Investigation). Appeals of the FERC’s decisions are pending before the United States Court of Appeals for the Ninth Circuit (Ninth Circuit).
	On March 7, 2014, Avista Utilities and Avista Energy filed at FERC a settlement with Pacific Gas & Electric (PG&E), Southern California Edison, San Diego Gas & Electric, the California Attorney General (AG), the California Department of Water Resources (CERS), and the California Public Utilities Commission (together, the “California Parties”) that resolves both the Trading Investigation and the Bidding Investigation. The settlement was approved by the FERC and is final so there is no longer any potential liability.
	California Refund Proceeding
	In July 2001, the FERC ordered an evidentiary hearing to determine the amount of refunds due to California energy buyers for purchases made in the spot markets operated by the CalISO and the CalPX during the period from October 2, 2000 to June 20, 2001 (Refund Period). Petitions for review of the FERC’s decisions are still pending in the Ninth Circuit. In August 2006, the Ninth Circuit remanded to the FERC its decision not to consider a Federal Power Act (FPA) section 309 remedy for tariff violations prior to October 2, 2000. During the FERC hearing on the remand in 2012, the Presiding Administrative Law Judge (ALJ) issued a partial initial decision granting Avista Utilities' motion for summary disposition. On November 2, 2012, the FERC issued an order affirming the partial initial decision and dismissing Avista Utilities from the proceeding. On February 15, 2013, the ALJ issued an Initial Decision that may have subjected Avista Energy to additional refund liability. Exceptions to the Initial Decision were filed and are pending before the FERC.
	On March 7, 2014, Avista Utilities, Avista Energy and the California Parties filed a settlement at the FERC that fully resolved these matters. Because Avista Energy had not been paid for all of its sales during the Refund Period, substantial funds have been held in escrow accounts pending resolution of this proceeding. The settlement returned $15.0 million of Avista Energy’s receivable to Avista Energy, with the balance of the Avista Energy receivable flowing to the purchasers associated with the hourly transactions at issue. The settlement funds were received on June 23, 2014 and recorded as a reduction to other operating expenses within the non-utility operating expenses section of the Condensed Consolidated Statements of Income. There is no admission of wrongdoing on the part of the settling parties and no part of the refund payment by Avista Energy constitutes a fine or a penalty. The settlement resolves all claims for alleged overcharges in the California Refund Proceeding, and in the Pacific Northwest Refund Proceeding (for sales made to CERS). The settlement also includes settlement of the Trading Investigation, the Bidding Investigation and the California Attorney General Complaint (the "Lockyer Complaint"). The settlement was approved by the FERC and is final so there is no longer any potential liability.
	California Attorney General Complaint (the “Lockyer Complaint”)
	In May 2002, the FERC dismissed a complaint filed in March 2002 by the California AG that alleged violations of the FPA by the FERC and all sellers (including Avista Corp. and its subsidiaries) of electric power and energy into California. The complaint alleged that the FERC's implementation of market-based rate authority was flawed and, as a result, individual sellers should refund the difference between the rate charged and a just and reasonable rate. In May 2002, the FERC issued an order dismissing the complaint. In September 2004, the Ninth Circuit upheld the FERC's market-based rate authority, but held that the FERC erred in ruling that it lacked authority to order refunds for violations of its reporting requirement. The Court remanded the case for further proceedings, which ultimately resulted in summary disposition at the FERC in favor of Avista Utilities and Avista Energy. The proceeding is now before the Ninth Circuit.
	On March 7, 2014, Avista Utilities, Avista Energy and the California Parties filed a settlement at the FERC that resolves this matter. The settlement was approved by the FERC and is final so there is no longer any potential liability.
	Pacific Northwest Refund Proceeding
	In July 2001, the Federal Energy Regulatory Commission (“FERC” or “Commission”) initiated a preliminary evidentiary hearing to develop a factual record as to whether prices for spot market sales of wholesale energy in the Pacific Northwest between December 25, 2000 and June 20, 2001 were just and reasonable. In June 2003, the FERC terminated the Pacific Northwest refund proceedings, after finding that the equities do not justify the imposition of refunds. In August 2007, the Ninth Circuit found that the FERC had failed to take into account new evidence of market manipulation and that such failure was arbitrary and capricious and, accordingly, remanded the case to the FERC, stating that the FERC's findings must be reevaluated in light of the new evidence. The Ninth Circuit expressly declined to direct the FERC to grant refunds. On October 3, 2011, the FERC issued an Order on Remand. On April 5, 2013, the FERC issued an Order on Rehearing expanding the temporal scope of the proceeding to permit parties to submit evidence on transactions during the period from January 1, 2000 through and including June 20, 2001. The Order on Remand established an evidentiary, trial-type hearing before an ALJ, and reopened the record to permit parties to present evidence of unlawful market activity. The Order on Remand stated that parties seeking refunds must submit evidence demonstrating that specific unlawful market activity occurred, and must demonstrate that such activity directly affected negotiations with respect to the specific contract rate about which they complain. Simply alleging a general link between the dysfunctional spot market in California and the Pacific Northwest spot market would not be sufficient to establish a causal connection between a particular seller's alleged unlawful activities and the specific contract negotiations at issue. The hearing was conducted in August through October 2013.
	On July 11, 2012 and March 28, 2013, Avista Energy and Avista Utilities filed settlements of all issues in this docket with regard to the claims made by the City of Tacoma and the California AG (on behalf of CERS). The FERC has approved the settlements and they are final. The remaining direct claimant against Avista Utilities and Avista Energy in this proceeding is the City of Seattle, Washington (Seattle).
	With regard to the Seattle claims, on March 28, 2014, the Presiding ALJ issued her Initial Decision finding that: 1) Seattle failed to demonstrate that either Avista Utilities or Avista Energy engaged in unlawful market activity and also failed to identify any specific contracts at issue; 2) Seattle failed to demonstrate that contracts with either Avista Utilities or Avista Energy imposed an excessive burden on consumers or seriously harmed the public interest; and that 3) Seattle failed to demonstrate that either Avista Utilities or Avista Energy engaged in any specific violations of substantive provisions of the Federal Power Act or any filed tariffs or rate schedules. Accordingly, the ALJ denied all of Seattle’s claims under both section 206 and section 309 of the Federal Power Act. Briefs on and opposing exceptions have been filed and the Initial Decision is pending before the Commission. The Company does not expect that this matter will have a material adverse effect on its financial condition, results of operations or cash flows.
	Sierra Club and Montana Environmental Information Center Litigation
	On March 6, 2013, the Sierra Club and Montana Environmental Information Center (MEIC) (collectively "Plaintiffs"), filed a Complaint in the United States District Court for the District of Montana, Billings Division, against the Owners of the Colstrip Generating Project ("Colstrip"). Avista Corp. owns a 15 percent interest in Units 3 & 4 of Colstrip. The other Colstrip co-Owners are PPL Montana, Puget Sound Energy, Portland General Electric Company, NorthWestern Energy and PacifiCorp. The Complaint alleges certain violations of the Clean Air Act, including the New Source Review, Title V and opacity requirements. The Plaintiffs request that the Court grant injunctive and declaratory relief, impose civil penalties, require a beneficial environmental project in the areas affected by the alleged air pollution and require payment of Plaintiffs' costs of litigation and attorney fees.
	On September 12, 2013, the Plaintiffs filed Plaintiffs’ First Motion for Partial Summary Judgment on the Applicable Method for Calculating Emission Increases from Modifications Made to the Colstrip Power Plant.
	On September 27, 2013, the Plaintiffs filed an Amended Complaint. The Amended Complaint withdrew from the original Complaint fifteen claims related to seven pre-January 1, 2001 Colstrip maintenance projects, upgrade projects and work projects and claims alleging violations of Title V and opacity requirements. The Amended Complaint alleges certain violations of the Clean Air Act and the New Source Review and adds claims with respect to post-January 1, 2001 Colstrip projects. The Plaintiffs request that the Court grant injunctive and declaratory relief, order remediation of alleged environmental damage, impose civil penalties, require a beneficial environmental project in the areas affected by the alleged air pollution and require payment of Plaintiffs’ costs of litigation and attorney fees. The Colstrip Owners filed a Motion to Dismiss, seeking dismissal of all of Plaintiffs' claims contained in the Amended Complaint.
	On May 22, 2014, the Magistrate Judge filed his Findings and Recommendations as to the motions and recommended that 1) the Colstrip Owners' Motion to Dismiss be granted as to the Plaintiffs' Best Available Control Technology claims and the injunctive relief sought regarding two of the claims, but denied the Motion in all other respects; and 2) the Plaintiffs' Motion for Partial Summary Judgment be denied. Plaintiffs' filed Objections to Findings and Recommendations of Magistrate Judge and the Colstrip Owners filed their response to Plaintiffs' objections.
	On August 27, 2014, the Plaintiffs filed a Second Amended Complaint. The Second Amended Complaint withdraws from the Amended Complaint five claims and adds one new claim. The Second Amended Complaint alleges certain violations of the Clean Air Act and the New Source Review. The Plaintiffs request that the Court grant injunctive and declaratory relief, order remediation of alleged environmental damages, impose civil penalties, require a beneficial environmental project in the areas affected by the alleged air pollution and require payment of Plaintiffs’ costs of litigation and attorney fees.
	The Court has set the trial date for August 2015.
	Management believes that it is reasonably possible that this matter could result in a loss to the Company. However, due to uncertainties concerning this matter, Avista Corp. cannot predict the outcome or determine whether it would have a material impact on the Company.
	Spokane River Licensing
	The Company owns and operates six hydroelectric plants on the Spokane River. Five of these (Long Lake, Nine Mile, Upper Falls, Monroe Street, and Post Falls) are regulated under one 50-year FERC license issued in June 2009 and are referred to as the Spokane River Project. The sixth, Little Falls, is operated under separate Congressional authority and is not licensed by the FERC. The license incorporated the 4(e) conditions that were included in the December 2008 Settlement Agreement with the United States Department of Interior and the Coeur d’Alene Tribe, as well as the mandatory conditions that were agreed to in the Idaho 401 Water Quality Certifications and in the amended Washington 401 Water Quality Certification.
	As part of the Settlement Agreement with the Washington Department of Ecology (Ecology), the Company has participated in the Total Maximum Daily Load (TMDL) process for the Spokane River and Lake Spokane, the reservoir created by Long Lake Dam. On May 20, 2010, the EPA approved the TMDL and on May 27, 2010, Ecology filed an amended 401 Water Quality Certification with the FERC for inclusion into the license. The amended 401 Water Quality Certification includes the Company's level of responsibility, as defined in the TMDL, for low dissolved oxygen levels in Lake Spokane. The Company submitted a draft Water Quality Attainment Plan for Dissolved Oxygen to Ecology in May 2012 and this was approved by Ecology in September 2012. This plan was subsequently approved by the FERC. The Company began implementing this plan in 2013, and management believes costs will not be material. On July 16, 2010, the City of Post Falls and the Hayden Area Regional Sewer Board filed an appeal with the United States District Court for the District of Idaho with respect to the EPA's approval of the TMDL. The Company, the City of Coeur d'Alene, Kaiser Aluminum and the Spokane River Keeper subsequently moved to intervene in the appeal. In September 2011, the EPA issued a stay to the litigation that will be in effect until either the permits are issued and all appeals and challenges are complete or the court lifts the stay. The stay is still in effect.
	During 2013, through a collaborative process with key stakeholders, a decision was reached to not move forward with a specific capital project to add oxygen to Lake Spokane. At the time of such decision, the Company had expended $1.3 million on the discontinued project. The Company obtained regulatory Orders from the UTC and IPUC during the second half of 2013, allowing regulatory treatment of the costs from the discontinued project.
	The UTC and IPUC approved the recovery of licensing costs through the general rate case settlements in 2009. The Company will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to implementing the license for the Spokane River Project.
	Cabinet Gorge Total Dissolved Gas Abatement Plan
	Dissolved atmospheric gas levels in the Clark Fork River exceed state of Idaho and federal water quality standards downstream of the Cabinet Gorge Hydroelectric Generating Project (Cabinet Gorge) during periods when excess river flows must be diverted over the spillway. Under the terms of the Clark Fork Settlement Agreement 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. In the second quarter of 2011, the Company completed preliminary feasibility assessments for several alternative abatement measures. In 2012, Avista Corp., with the approval of the Clark Fork Management Committee (created under the Clark Fork Settlement Agreement), moved forward to test one of the alternatives by constructing a spill crest modification on a single spill gate. Based on testing in 2013, the modification appears to provide significant Total Dissolved Gas reduction. Ongoing design improvements have been made, and the Company expects to continue spill crest modifications over the next several years, in ongoing consultation with key stakeholders. The Company will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to this issue.
	Fish Passage at Cabinet Gorge and Noxon Rapids
	In 1999, the United States Fish and Wildlife Service (USFWS) listed bull trout as threatened under the Endangered Species Act. The Clark Fork Settlement Agreement describes programs intended to help restore bull trout populations in the project area. Using the concept of adaptive management and working closely with the USFWS, the Company evaluated the feasibility of fish passage at Cabinet Gorge and Noxon Rapids. The results of these studies led, in part, to the decision to move forward with development of permanent facilities, among other bull trout enhancement efforts. Fishway designs for Cabinet Gorge are still being finalized. Construction cost estimates and schedules will be developed after several remaining issues are resolved, related to Montana's approval of fish transport from Idaho and expected minimum discharge requirements. Fishway design for Noxon Rapids has also been initiated, and is still in early stages.
	In January 2010, the USFWS revised its 2005 designation of critical habitat for the bull trout to include the lower Clark Fork River as critical habitat. The Company believes its ongoing efforts through the Clark Fork Settlement Agreement continue to effectively address issues related to bull trout. The Company will continue to seek recovery, through the ratemaking process, of all operating and capitalized costs related to fish passage at Cabinet Gorge and Noxon Rapids.
	Kettle Falls Generation Station - Diesel Spill Investigation and Remediation
	On December 24, 2013, the Company's operations staff at the Kettle Falls Generation Station discovered that approximately 10,000 gallons of diesel fuel had leaked underground from the piping system used to fuel heavy equipment. Avista Corp. made all proper agency notifications and worked closely with the Washington State Department of Ecology (Ecology) during the spill response and investigation phase. The Company installed ground water monitoring wells and there is no indication that ground or surface water is threatened by the spill.
	There is no indication from Ecology that Ecology is considering any enforcement action and the Company initiated a voluntary cleanup action with the installation of a recovery system.
	As of September 30, 2014, the Company has recorded an estimated remediation liability and the Company will continue to monitor the remediation activities and will adjust any estimated remediation liability if necessary as new information is obtained. The Company does not expect that this matter will have a material effect on its financial condition, results of operations or cash flows.
	Collective Bargaining Agreements
	The Company’s collective bargaining agreements with the International Brotherhood of Electrical Workers represent approximately 45 percent of all of Avista Utilities’ employees. The agreement with the local union in Washington and Idaho representing the majority (approximately 90 percent) of the Avista Utilities' bargaining unit employees expired in March 2014. A new three-year agreement in Oregon, which covers approximately 50 employees, was approved in April 2014. Negotiations are currently ongoing with respect to the expired labor agreement in Washington and Idaho and the Company does not expect any disruption to its operations.
	A new collective bargaining agreement with the local union of the IBEW in Alaska was signed in May 2013 and expires in March 2017. The collective bargaining agreement with the IBEW in Alaska represents approximately 54 percent of all AERC employees.
	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.

Information_By_Business_Segmen

Information By Business Segments	9 Months Ended
	Sep. 30, 2014
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. Ecova was a provider of facility information and cost management services for multi-site customers throughout North America. The Ecova business segment has been disposed of as of June 30, 2014. All income statement amounts have been reclassified to discontinued operations on the Condensed Consolidated Statements of Income for all periods presented. The Other category, which is not a reportable segment, includes Spokane Energy, other investments and operations of various subsidiaries, as well as certain other operations of Avista Capital. On July 1, 2014, the Company completed its acquisition of AERC. Based on the way AERC is managed and the financial reports that are reviewed by the Chief Operating Decision Maker, AEL&P, the primary subsidiary of AERC is considered a separate reportable business segment and the remaining activities of AERC are included in the Other category. All goodwill associated with the AERC acquisition has been assigned to the AEL&P reportable business segment.
	The following table presents information for each of the Company’s business segments (dollars in thousands):
		Avista		Alaska Electric Light and Power Company		Total Utility		Other			Intersegment			Total
		Utilities									Eliminations
											-1
	For the three months ended September 30, 2014:
	Operating revenues	$	282,555	$	9,157	$	291,712	$	10,296		$	(450	)	$	301,558
	Resource costs	128,591		2,997		131,588		—			—			131,588
	Other operating expenses	69,403		3,106		72,509		10,701			(450		)	82,760
	Depreciation and amortization	32,006		1,288		33,294		154			—			33,448
	Income (loss) from operations	32,048		1,273		33,321		(559		)	—			32,762
	Interest expense (2)	18,247		485		18,732		186			(163		)	18,755
	Income taxes	7,146		329		7,475		(174		)	—			7,301
	Net income (loss) from continuing operations attributable to Avista Corp. shareholders	10,349		511		10,860		(354		)	—			10,506
	Capital expenditures (3)	92,197		1,053		93,250		194			—			93,444
	For the three months ended September 30, 2013:
	Operating revenues	$	278,923	$	—	$	278,923	$	11,004		$	(450	)	$	289,477
	Resource costs	131,136		—		131,136		—			—			131,136
	Other operating expenses	69,596		—		69,596		10,662			(450		)	79,808
	Depreciation and amortization	29,823		—		29,823		171			—			29,994
	Income from operations	29,657		—		29,657		170			—			29,827
	Interest expense (2)	18,837		—		18,837		525			(77		)	19,285
	Income taxes	3,945		—		3,945		(578		)	—			3,367
	Net income (loss) from continuing operations attributable to Avista Corp. shareholders	9,447		—		9,447		(1,074		)	77			8,450
	Capital expenditures (3)	75,368		—		75,368		24			—			75,392
	For the nine months ended September 30, 2014:
	Operating revenues	$	1,023,684	$	9,157	$	1,032,841	$	29,225		$	(1,350	)	$	1,060,716
	Resource costs	478,010		2,997		481,007		—			—			481,007
	Other operating expenses	204,089		3,106		207,195		21,864			(1,350		)	227,709
	Depreciation and amortization	93,912		1,288		95,200		452			—			95,652
	Income from operations	177,653		1,273		178,926		6,909			—			185,835
	Interest expense (2)	55,215		485		55,700		899			(330		)	56,269
	Income taxes	48,068		329		48,397		2,877			—			51,274
	Net income from continuing operations attributable to Avista Corp. shareholders	85,030		511		85,541		3,528			167			89,236
	Capital expenditures (3)	228,711		1,053		229,764		296			—			230,060
		Avista		Alaska Electric Light and Power Company		Total Utility		Other			Intersegment			Total
		Utilities									Eliminations
											-1
	For the nine months ended September 30, 2013:
	Operating revenues	$	1,008,669	$	—	$	1,008,669	$	30,145		$	(1,350	)	$	1,037,464
	Resource costs	487,277		—		487,277		—			—			487,277
	Other operating expenses	200,824		—		200,824		30,322			(1,350		)	229,796
	Depreciation and amortization	86,783		—		86,783		536			—			87,319
	Income (loss) from operations	167,648		—		167,648		(713		)	—			166,935
	Interest expense (2)	56,635		—		56,635		1,801			(230		)	58,206
	Income taxes	43,278		—		43,278		(1,349		)	—			41,929
	Net income (loss) from continuing operations attributable to Avista Corp. shareholders	76,265		—		76,265		(2,613		)	230			73,882
	Capital expenditures (3)	220,712		—		220,712		139			—			220,851
	Total Assets:
	As of September 30, 2014:	$	3,991,330	$	261,402	$	4,252,732	$	83,614		$	—		$	4,336,346
	As of December 31, 2013 (4):	$	3,940,998	$	—	$	3,940,998	$	81,282		$	—		$	4,022,280
	-1	Intersegment eliminations reported as operating revenues and resource costs represent intercompany purchases and sales of electric capacity and energy. Intersegment eliminations reported as interest expense and net income (loss) attributable to Avista Corp. shareholders represent intercompany interest.
	-2	Including interest expense to affiliated trusts.
	-3	The capital expenditures for the other businesses are included as other capital expenditures on the Condensed Consolidated Statements of Cash Flows. The remainder of the balance included in other capital expenditures on the Condensed Consolidated Statements of Cash Flows are related to Ecova.
	-4	The consolidated total assets presented here as of December 31, 2013 exclude total assets at Ecova of $339.6 million.

Summary_Of_Significant_Account1

Summary Of Significant Accounting Policies (Policy)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Share Repurchase Program Policy [Policy Text Block]	'
	Stock Repurchase Program
	On June 13, 2014, Avista Corp.'s Board of Directors approved a program to repurchase up to 4 million shares of the Company’s outstanding common stock, assuming the closure of the Ecova transaction. Repurchases of common stock under this program commenced on July 7, 2014 and the program expires on December 31, 2014. The Company can choose to terminate the repurchase program before December 31, 2014. Repurchases are made in the open market or in privately negotiated transactions. There is no assurance that the goal of repurchasing 4 million shares will be achieved. Through October 31, 2014, the Company has repurchased 2,529,615 shares at a total cost of $79.9 million and an average cost of $31.57 per share. All repurchased shares revert to the status of authorized but unissued shares.
Dividends [Policy Text Block]	'
	Dividends
	The payment of dividends on common stock could be limited by:
	•	certain covenants applicable to preferred stock (when outstanding) contained in the Company’s Restated Articles of Incorporation, as amended (currently there are no preferred shares outstanding),
	•	certain covenants applicable to the Company's outstanding long-term debt and committed line of credit agreements,
	•	the hydroelectric licensing requirements of section 10(d) of the FPA, and
	•	certain requirements under the OPUC approval of the AERC acquisition, which does not permit one-time or special dividends from AERC to Avista Corp. and which does not permit Avista Utilities' total equity to total capitalization to be less than 40 percent, without approval from the OPUC. The OPUC approval does allow for special or one-time dividends during the first year after closing to recapitalize AERC as part of the transaction and it also allows for regular distributions of AERC earnings to Avista Corp. as long as AERC remains sufficiently capitalized and insured.
	Under the covenant applicable to the Company's committed line of credit agreement, which does not permit the ratio of “consolidated total debt” to “consolidated total capitalization” to be greater than 65 percent at any time, the amount of retained earnings available for dividends at September 30, 2014 was limited to approximately $441.1 million.
	Under the requirements of the OPUC approval of the AERC acquisition as outlined above, the amount available for dividends at September 30, 2014 was limited to approximately $291.0 million.
Appropriated Retained Earnings [Policy Text Block]	'
	Appropriated Retained Earnings
	In accordance with the hydroelectric licensing requirements of section 10(d) of the Federal Power Act (FPA), the Company maintains an appropriated retained earnings account for any earnings in excess of the specified rate of return on the Company's investment in the licenses for its various hydroelectric projects. The rate of return on investment is specified in the various hydroelectric licensing agreements for the Clark Fork River and Spokane River. Per section 10(d) of the FPA, the Company must maintain these excess earnings in an appropriated retained earnings account until the termination of the licensing agreements or apply them to reduce the net investment in the licenses of the hydroelectric projects at the discretion of the FERC. The Company typically calculates the earnings in excess of the specified rate of return on an annual basis, usually during the second quarter.
	In addition to the hydroelectric project licenses identified above for Avista Utilities, the requirements of section 10(d) of the FPA also apply to the Lake Dorothy, the Annex Creek and the Salmon Creek licenses, which were all acquired in the AERC acquisition. The Company is still evaluating these licenses to determine an appropriate amount of appropriated retained earnings to record and this analysis is expected to be completed in 2015. The Company does not expect this to result in a material amount of appropriated retained earnings.
	The appropriated retained earnings amounts included in retained earnings were as follows as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,				December 31,
		2014				2013
	Appropriated retained earnings	$	14,270			$	9,714
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 the 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 Avista Utilities' Noxon Rapids generating facility.
	On July 1, 2014, Avista Corp. completed its acquisition of Alaska Energy and Resources Company (AERC), and as of that date, AERC is a wholly-owned subsidiary of Avista Corp. The primary subsidiary of AERC is Alaska Electric Light and Power Company (AEL&P), comprising the regulated utility operations in Alaska. Beginning with the three months ended September 30, 2014, the results of AERC are included in the overall results of Avista Corp. See Note 4 for information regarding the acquisition of AERC.
	Avista Capital, Inc. (Avista Capital), a wholly owned subsidiary of Avista Corp., is the parent company of all of the subsidiary companies in the non-utility businesses, except Spokane Energy, LLC (Spokane Energy). During the first half of the year, Avista Capital’s subsidiaries included Ecova, Inc. (Ecova), which was an 80.2 percent owned subsidiary prior to its disposition on June 30, 2014. Ecova was a provider of energy efficiency and other facility information and cost management programs and services for multi-site customers and utilities throughout North America. See Note 5 for information regarding the disposition of Ecova and Note 13 for business segment information.
Basis Of Reporting	'
	Basis of Reporting
	The condensed consolidated financial statements include the assets, liabilities, revenues and expenses of the Company and its subsidiaries and other majority owned subsidiaries and variable interest entities for which the Company or its subsidiaries are the primary beneficiaries. Ecova's revenues and expenses are included in the Condensed Consolidated Statements of Income in discontinued operations; however, as of June 30, 2014 and for all subsequent reporting periods there are no balance sheet amounts included for Ecova. 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.
Taxes Other Than Income Taxes	'
	Taxes Other Than Income Taxes
	Taxes other than income taxes include state excise taxes, city occupational and franchise taxes, real and personal property taxes and certain other taxes not based on net income. These taxes are generally based on revenues or the value of property. Utility related taxes collected from customers (primarily state excise taxes and city utility taxes) are recorded as operating revenue and expense and totaled the following amounts for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Utility taxes	$	11,716			$	10,901			$	43,923			$	41,045
Other Income - Net	'
	Other Income-Net
	Other income-net consisted of the following items for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Interest income	$	154			$	124			$	678			$	620
	Interest income on regulatory deferrals	59				27				154				48
	Equity-related AFUDC	2,189				1,595				6,426				4,341
	Net gain/(loss) on investments	(27		)		(1,299		)		118				(1,543		)
	Other income	233				41				887				973
	Total	$	2,608			$	488			$	8,263			$	4,439
Materials And Supplies, Fuel Stock And Natural Gas Stored	'
	Materials and Supplies, Fuel Stock and Natural Gas Stored
	Inventories of materials and supplies, fuel stock and natural gas stored 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 September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,				December 31,
		2014				2013
	Materials and supplies	$	31,226			$	28,747
	Fuel stock	5,170				3,170
	Natural gas stored	33,545				13,029
	Total	$	69,941			$	44,946
Investments And Funds Held For Clients And Client Fund Obligations	'
	Investments and Funds Held for Clients and Client Fund Obligations
	In connection with its bill paying services, Ecova collected funds from its clients and remitted the funds to the appropriate utility or other service provider. Some of the funds collected were invested by Ecova and classified as investments and funds held for clients, and a related liability for client fund obligations was recorded. Investments and funds held for clients included cash and cash equivalent investments, money market funds and investment securities classified as available for sale. Ecova did not invest the funds directly for the clients' benefit; therefore, Ecova bore the risk of loss associated with the investments. As of June 30, 2014 and for all subsequent reporting periods there are no longer any investments and funds held for clients due to the disposition of Ecova.
	Investments and funds held for clients as of December 31, 2013 were as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	16,147			$	—			$	16,147
	Money market funds	11,180				—				11,180
	Securities available for sale:
	U.S. government agency	63,633				(2,555		)		61,078
	Municipal	3,497				21				3,518
	Corporate fixed income – financial	3,000				—				3,000
	Corporate fixed income – industrial	753				12				765
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	71,883				(2,522		)		69,361
	Total investments and funds held for clients	$	99,210			$	(2,522	)		$	96,688
	-1	Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.
	Investments and funds held for clients were classified as a current asset since these funds were held for the purpose of satisfying the client fund obligations. As of December 31, 2013, approximately 95 percent of the investment portfolio was rated AA-, Aa3 and higher by nationally recognized statistical rating organizations. All fixed income securities were rated as investment grade as of December 31, 2013.
	Ecova management reviewed its investments continuously for indicators of other-than-temporary impairment. To make this determination, management employed a methodology that considers available quantitative and qualitative evidence in evaluating potential impairment of its investments. If the cost of an investment exceeded its fair value, management evaluated, among other factors, general market conditions, credit quality of instrument issuers, the length of time and extent to which the fair value was less than cost, and whether it had plans to sell the security or it was more-likely-than not that the Company would be required to sell the security before recovery. Management also considered specific adverse conditions related to the financial health of and specific prospects for the issuer as well as other cash flow factors. Once a decline in fair value was determined to be other-than-temporary, an impairment charge was recorded in earnings and a new cost basis in the investment was established. Based on management’s analysis, securities available for sale did not meet the criteria for other-than-temporary impairment as of December 31, 2013.
	The following is a summary of the disposition of available-for-sale securities for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Proceeds from sales, maturities and calls	$	—			$	1,825			$	14,612			$	16,955
	Gross realized gains	—				2				3				20
	Gross realized losses (1)	—				—				(735		)		—
	-1	The gross realized losses for the nine months ended September 30, 2014 were included in the determination of the gain on the disposal of Ecova and were not the result of selling any individual securities.
	Contractual maturities of securities available for sale as of December 31, 2013 are as follows (dollars in thousands):
		Due within 1 year			After 1 but within 5 years			After 5 but within 10 years			After 10 years			Total
	31-Dec-13	5,382			12,745			48,310			2,924			69,361
	Actual maturities may differ due to call or prepayment rights and the effective maturity was 3.0 years as of December 31, 2013.
Goodwill	'
	Goodwill
	Goodwill arising from acquisitions represents the excess of the purchase price over the estimated fair value of net assets acquired. The Company evaluates goodwill for impairment using a combination of the discounted cash flow model and a market approach on at least an annual basis or more frequently if impairment indicators arise. The Company completed its annual evaluation of goodwill for potential impairment as of December 31, 2013 for Ecova and as of November 30, 2013 for the other businesses and determined that goodwill was not impaired at that time. Avista Corp. will use November 30, 2014 for its annual evaluation of goodwill related to AEL&P and the other businesses for 2014.
	The changes in the carrying amount of goodwill are as follows (dollars in thousands):
		Ecova				AEL&P				Other				Accumulated				Total
														Impairment
														Losses
	31-Dec-13	$	71,011			$	—			$	12,979			$	(7,733	)		$	76,257
	Adjustments	112				—				—				—				112
	Goodwill sold during the year	(71,123		)		—				—				—				(71,123		)
	Goodwill acquired during the year	—				50,631				—				—				50,631
	Balance as of September 30, 2014	$	—			$	50,631			$	12,979			$	(7,733	)		$	55,877
	Accumulated impairment losses are attributable to the other businesses. The goodwill sold during the year relates to the Ecova disposition, which occurred on June 30, 2014. See Note 5 for information regarding this sales transaction. The goodwill acquired during the year relates to the acquisition of AERC and the goodwill associated with this acquisition is not deductible for tax purposes. See Note 4 for information regarding this business acquisition and Note 13 regarding the Company's reportable segments.
Other Intangibles	'
	Intangible Assets
	Amortization expense related to intangible assets was as follows for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Intangible asset amortization	$	—			$	2,765			$	5,898			$	8,442
	All of the intangible assets were related to Ecova, which was disposed of as of June 30, 2014. As such, there are no intangible assets remaining as of September 30, 2014 and there is no amortization expense expected for the remainder of the year and in future years. The amortization expense disclosed in the table above is included in discontinued operations for all periods presented. See Note 5 for information regarding the Ecova sales transaction.
	The gross carrying amount and accumulated amortization of intangible assets as of December 31, 2013 are as follows (dollars in thousands):
		Estimated		December 31,
		Useful Lives		2013
	Client relationships	2 - 12 years		$	33,562
	Software development costs	3 - 7 years		39,327
	Other	1 - 10 years		3,321
	Total intangible assets			76,210
	Client relationships accumulated amortization			(12,336		)
	Software development costs accumulated amortization			(21,861		)
	Other accumulated amortization			(2,437		)
	Total accumulated amortization			(36,634		)
	Total intangible assets - net			$	39,576
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. In certain defined conditions, a derivative may be specifically designated as a hedge for a particular exposure. The accounting for a derivative depends on the intended use of such derivative and the resulting designation.
	The Washington Utilities and Transportation Commission (UTC) and the Idaho Public Utilities Commission (IPUC) issued accounting orders authorizing Avista Utilities 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. The orders provide for Avista Utilities to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the periods of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the Energy Recovery Mechanism (ERM) in Washington, the Power Cost Adjustment (PCA) mechanism in Idaho, and periodic general rates cases. Regulatory assets are assessed regularly and are probable for 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 agreements, each period Avista Utilities records all mark-to-market gains and losses for its interest rate swaps agreements as assets and liabilities and records offsetting regulatory assets and liabilities, such that there is no income statement impact. This is similar to the treatment of energy commodity derivatives described above. Upon settlement of interest rate swaps, the regulatory asset or liability (included as part of long-term debt) is amortized as a component of interest expense over the term of the associated debt.
Fair Value Measurements	'
	Fair Value Measurements
	Fair value represents the price that would be received to sell 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, investments and funds held for clients, deferred compensation assets, as well as derivatives related to interest rate swap agreements and foreign currency exchange contracts, are reported at estimated fair value on the Condensed Consolidated Balance Sheets. See Note 10 for the Company’s fair value disclosures.
Regulatory Deferred Charges And Credits	'
	Regulatory Deferred Charges and Credits
	The Company prepares its condensed consolidated financial statements in accordance with regulatory accounting practices because:
	•	rates for regulated services are established by or subject to approval by independent third-party regulators,
	•	the regulated rates are designed to recover the cost of providing the regulated services, and
	•	in view of demand for the regulated services and the level of competition, it is reasonable to assume that rates can be charged to and collected from customers at levels that will recover costs.
	Regulatory accounting practices require that certain costs and/or obligations (such as incurred power and natural gas costs not currently included in rates, but expected to be recovered or refunded in the future) are reflected as deferred charges or credits on the Condensed Consolidated Balance Sheets. These costs and/or obligations are not reflected in the Condensed Consolidated Statements of Income until the period during which matching revenues are recognized. If at some point in the future the Company determines that it no longer meets the criteria for continued application of regulatory accounting practices for all or a portion of its regulated operations, the Company could be:
	•	required to write off its regulatory assets, and
	•	precluded from the future deferral of costs not recovered through rates at the time such costs are incurred, even if the Company expected to recover such costs in the future.
Redeemable Noncontrolling Interests [Policy Text Block]	'
	Redeemable Noncontrolling Interests
	At December 31, 2013, certain option holders of Ecova had the right to put their shares back to Ecova at their discretion during an annual put window. Stock options and other outstanding redeemable stock were valued at their maximum redemption amount which was equal to their intrinsic value (fair value less exercise price). Due to the disposition of Ecova, as of June 30, 2014 there are no longer any redeemable noncontrolling interests.
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 losses that do not meet these conditions for accrual, if there is a reasonable possibility that a loss may be incurred.
Accumulated Other Comprehensive Loss [Policy Text Block]	'
	Accumulated Other Comprehensive Loss
	Accumulated other comprehensive loss, net of tax, consisted of the following as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,				December 31,
		2014				2013
	Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $(2,099) and $(2,280), respectively	$	(3,898	)		$	(4,233	)
	Unrealized loss on securities available for sale - net of taxes of $0 and $(936), respectively (1)	—				(1,586		)
	Total accumulated other comprehensive loss	$	(3,898	)		$	(5,819	)
	-1	This entire balance was related to Ecova, which was disposed of as of June 30, 2014.
	The following table details the reclassifications out of accumulated other comprehensive loss by component for the three and nine months ended September 30 (dollars in thousands):
			Amounts Reclassified from Accumulated Other Comprehensive Loss
			Three months ended September 30,								Nine months ended September 30,
	Details about Accumulated Other Comprehensive Loss Components		2014				2013				2014				2013				Affected Line Item in Statement of Income
	Realized gains on investment securities		$	—			$	2			$	3			$	20			(a)
	Realized losses on investment securities		—				—				(735		)		—				(a)
			—				2				(732		)		20				Total before tax
			—				(1		)		272				(8		)		Tax benefit (expense) (a)
			$	—			$	1			$	(460	)		$	12			Net of tax
	Amortization of defined benefit pension items
	Amortization of net loss		$	(1,951	)		$	(4,891	)		$	(5,855	)		$	(14,673	)		(b)
	Adjustment due to effects of regulation		1,779				4,608				5,339				13,825				(b)
			(172		)		(283		)		(516		)		(848		)		Total before tax
			60				99				181				297				Tax benefit
			$	(112	)		$	(184	)		$	(335	)		$	(551	)		Net of tax
	(a)	These amounts were included as part of net income from discontinued operations for all periods presented (see Note 5 for additional details).
	(b)	These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details).

Summary_Of_Significant_Account2

Summary Of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Schedule of common stock repurchased [Table Text Block]	'
	The following table provides information about share repurchases that Avista Corp. made during the three months ended September 30, 2014 (in thousands, except per share amounts):
		Total Number of Shares Purchased			Average Price Paid per Share				Total Number of Shares Purchased as Part of Publicly Announced Program			Maximum Number of Shares that May Yet Be Purchased Under the Program
	July 1 to July 31, 2014	292			$	32.3			292			3,708
	August 1 to August 31, 2014	927			31.5				927			2,781
	September 1 to September 30, 2014	705			31.67				705			2,076
	Total	1,924			$	31.68			1,924			2,076
Appropriated Retained Earnings [Table Text Block]	'
	The appropriated retained earnings amounts included in retained earnings were as follows as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,				December 31,
		2014				2013
	Appropriated retained earnings	$	14,270			$	9,714
Schedule of Accumulated Other Comprehensive Income (Loss)	'
	Accumulated other comprehensive loss, net of tax, consisted of the following as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,				December 31,
		2014				2013
	Unfunded benefit obligation for pensions and other postretirement benefit plans - net of taxes of $(2,099) and $(2,280), respectively	$	(3,898	)		$	(4,233	)
	Unrealized loss on securities available for sale - net of taxes of $0 and $(936), respectively (1)	—				(1,586		)
	Total accumulated other comprehensive loss	$	(3,898	)		$	(5,819	)
Reclassifications Out of Accumulated Other Comprehensive Loss by Component	'
	The following table details the reclassifications out of accumulated other comprehensive loss by component for the three and nine months ended September 30 (dollars in thousands):
			Amounts Reclassified from Accumulated Other Comprehensive Loss
			Three months ended September 30,								Nine months ended September 30,
	Details about Accumulated Other Comprehensive Loss Components		2014				2013				2014				2013				Affected Line Item in Statement of Income
	Realized gains on investment securities		$	—			$	2			$	3			$	20			(a)
	Realized losses on investment securities		—				—				(735		)		—				(a)
			—				2				(732		)		20				Total before tax
			—				(1		)		272				(8		)		Tax benefit (expense) (a)
			$	—			$	1			$	(460	)		$	12			Net of tax
	Amortization of defined benefit pension items
	Amortization of net loss		$	(1,951	)		$	(4,891	)		$	(5,855	)		$	(14,673	)		(b)
	Adjustment due to effects of regulation		1,779				4,608				5,339				13,825				(b)
			(172		)		(283		)		(516		)		(848		)		Total before tax
			60				99				181				297				Tax benefit
			$	(112	)		$	(184	)		$	(335	)		$	(551	)		Net of tax
	(a)	These amounts were included as part of net income from discontinued operations for all periods presented (see Note 5 for additional details).
	(b)	These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details).
Utility Taxes	'
	Utility related taxes collected from customers (primarily state excise taxes and city utility taxes) are recorded as operating revenue and expense and totaled the following amounts for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Utility taxes	$	11,716			$	10,901			$	43,923			$	41,045
Other Income - Net	'
	Other income-net consisted of the following items for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Interest income	$	154			$	124			$	678			$	620
	Interest income on regulatory deferrals	59				27				154				48
	Equity-related AFUDC	2,189				1,595				6,426				4,341
	Net gain/(loss) on investments	(27		)		(1,299		)		118				(1,543		)
	Other income	233				41				887				973
	Total	$	2,608			$	488			$	8,263			$	4,439
Materials And Supplies Fuel Stock And Natural Gas Stored	'
	Inventories of materials and supplies, fuel stock and natural gas stored 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 September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,				December 31,
		2014				2013
	Materials and supplies	$	31,226			$	28,747
	Fuel stock	5,170				3,170
	Natural gas stored	33,545				13,029
	Total	$	69,941			$	44,946
Investments And Funds Held For Clients	'
	Investments and funds held for clients as of December 31, 2013 were as follows (dollars in thousands):
		Amortized				Unrealized				Fair Value
		Cost (1)				Gain (Loss)
	Cash and cash equivalents	$	16,147			$	—			$	16,147
	Money market funds	11,180				—				11,180
	Securities available for sale:
	U.S. government agency	63,633				(2,555		)		61,078
	Municipal	3,497				21				3,518
	Corporate fixed income – financial	3,000				—				3,000
	Corporate fixed income – industrial	753				12				765
	Certificates of deposit	1,000				—				1,000
	Total securities available for sale	71,883				(2,522		)		69,361
	Total investments and funds held for clients	$	99,210			$	(2,522	)		$	96,688
	-1	Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.
Contractual Maturities Of Securities Available For Sale	'
	Contractual maturities of securities available for sale as of December 31, 2013 are as follows (dollars in thousands):
		Due within 1 year			After 1 but within 5 years			After 5 but within 10 years			After 10 years			Total
	31-Dec-13	5,382			12,745			48,310			2,924			69,361
Goodwill	'
	The changes in the carrying amount of goodwill are as follows (dollars in thousands):
		Ecova				AEL&P				Other				Accumulated				Total
														Impairment
														Losses
	31-Dec-13	$	71,011			$	—			$	12,979			$	(7,733	)		$	76,257
	Adjustments	112				—				—				—				112
	Goodwill sold during the year	(71,123		)		—				—				—				(71,123		)
	Goodwill acquired during the year	—				50,631				—				—				50,631
	Balance as of September 30, 2014	$	—			$	50,631			$	12,979			$	(7,733	)		$	55,877
Other Intangible Amortization	'
	Amortization expense related to intangible assets was as follows for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Intangible asset amortization	$	—			$	2,765			$	5,898			$	8,442
Accumulated Amortization Of Other Intangibles	'
	The gross carrying amount and accumulated amortization of intangible assets as of December 31, 2013 are as follows (dollars in thousands):
		Estimated		December 31,
		Useful Lives		2013
	Client relationships	2 - 12 years		$	33,562
	Software development costs	3 - 7 years		39,327
	Other	1 - 10 years		3,321
	Total intangible assets			76,210
	Client relationships accumulated amortization			(12,336		)
	Software development costs accumulated amortization			(21,861		)
	Other accumulated amortization			(2,437		)
	Total accumulated amortization			(36,634		)
	Total intangible assets - net			$	39,576
Disposition of Available-for-Sale Securities	'
	The following is a summary of the disposition of available-for-sale securities for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,								Nine months ended September 30,
		2014				2013				2014				2013
	Proceeds from sales, maturities and calls	$	—			$	1,825			$	14,612			$	16,955
	Gross realized gains	—				2				3				20
	Gross realized losses (1)	—				—				(735		)		—

Business_Acquisitions_Tables

Business Acquisitions (Tables)	9 Months Ended
	Sep. 30, 2014
Business Acquisition [Line Items]	'
Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable [Table Text Block]	'
	The contract acquisition price and the fair value of consideration transferred for AERC as of July 1, 2014 were as follows (in thousands):
		1-Jul-14
	Contract acquisition price (using the calculated $32.46 per share common stock price)
	Gross contract price	$	170,000
	Acquired cash	19,704
	Acquired debt (excluding capital lease obligation)	(38,832		)
	Other closing adjustments	(104		)
	Total adjusted contract price	$	150,768
	Fair value of consideration transferred
	Avista Corp. common stock (4,500,014 shares at $33.35 per share)	$	150,075
	Cash	4,697
	Fair value of total consideration transferred	$	154,772
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	'
	The preliminary estimated fair value of assets acquired and liabilities assumed as of July 1, 2014 were as follows (in thousands):
		1-Jul-14
	Assets acquired:
	Current Assets:
	Cash	$	19,704
	Accounts receivable - gross totals $3,928	3,851
	Materials and supplies	2,017
	Other current assets	999
	Total current assets	26,571
	Utility Property:
	Utility plant in service	113,964
	Utility property under long-term capital lease	71,007
	Construction work in progress	3,440
	Total utility property	188,411
	Other Non-current Assets:
	Non-utility property	6,660
	Electric plant held for future use	3,711
	Goodwill	50,631
	Other deferred charges and non-current assets	5,368
	Total other non-current assets	66,370
	Total assets	$	281,352
	Liabilities Assumed:
	Current Liabilities:
	Accounts payable	$	700
	Current portion of long-term debt and capital lease obligations	3,773
	Other current liabilities	2,902
	Total current liabilities	7,375
	Long-term debt	37,227
	Capital lease obligations	68,840
	Other non-current liabilities and deferred credits	13,138
	Total liabilities	$	126,580
	Total identifiable net assets acquired	$	154,772
Business Acquisition, Pro Forma Information [Table Text Block]	'
	The following table summarizes the supplemental pro forma revenue, net income and earnings per share information for the three and nine months ended September 30 related to the acquisition of AERC as if the acquisition had occurred on January 1, 2013. The revenues and net income for AERC for the three months ended September 30, 2014 are actual results and the results for the first nine months of 2013 and the first six months of 2014 are pro forma results (dollars in thousands):
		Three months ended September 30,					Nine months ended September 30,
		2014			2013		2014		2013
	Actual Avista Corp. revenues from continuing operations (excluding AERC)	$	292,334		$	289,477	$	1,051,492	$	1,037,464
	Supplemental pro forma AERC revenues (1)	9,224			9,309		35,319		31,243
	Total supplemental pro forma revenues	301,558			298,786		1,086,811		1,068,707
	Actual AERC revenues included in Avista Corp. revenues (1)	9,224			—		9,224		—
	Actual Avista Corp. net income from continuing operations attributable to Avista Corp. shareholders (excluding AERC)	9,982			8,450		88,712		73,882
	Actual Avista Corp. net income from discontinued operations attributable to Avista Corp. shareholders	(55		)	2,963		70,585		5,529
	Adjustment to Avista Corp.'s net income for acquisition costs (net of tax) (2)	401			66		838		(1,828		)
	Supplemental pro forma AERC net income (1) (5)	524			199		6,151		7,634
	Total supplemental pro forma net income	10,852			11,678		166,286		85,217
	Actual AERC net income included in Avista Corp. net income (1)	$	524		$	—	$	524	$	—
	Pro forma weighted-average common shares outstanding (thousands), basic (3)	63,934			64,494		64,413		64,433
	Pro forma weighted-average common shares outstanding (thousands), diluted (3)	64,244			64,532		64,625		64,464
	Pro forma earnings per common share attributable to Avista Corp. shareholders
	Total pro forma earnings per common share attributable to Avista Corp. shareholders, basic	$	0.17		$	0.18	$	2.58	$	1.32
	Total pro forma earnings per common share attributable to Avista Corp. shareholders, diluted (4)	$	0.17		$	0.18	$	2.57	$	1.32

Discontinued_Operations_Discon1

Discontinued Operations Discontinued Operations (Tables)	9 Months Ended
	Sep. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	'
	The major classes of assets and liabilities and their carrying amounts immediately prior to the completion of the sales transaction were as follows:
		30-Jun-14
	Assets:
	Current Assets:
	Cash and cash equivalents	$	95,932
	Accounts and notes receivable-less allowances of $410	32,070
	Investments and funds held for clients	114,598
	Income taxes receivable	2,548
	Other current assets	8,908
	Total current assets	254,056
	Other Non-current Assets:
	Goodwill	71,123
	Intangible assets-net of accumulated amortization of $42,266	37,185
	Other property and investments-net	4,656
	Total other non-current assets	112,964
	Total assets	367,020
	Liabilities:
	Current Liabilities:
	Accounts payable	72,453
	Client fund obligations	115,333
	Current portion of long-term debt	67
	Other current liabilities	35,329
	Total current liabilities	223,182
	Long-term borrowings under committed line of credit	40,000
	Other non-current liabilities	2,117
	Total liabilities	$	265,299
Summary of Cash Proceeds from Sale of Discontinued Operations [Table Text Block]	'
	The summary of cash proceeds associated with the sales transaction are as follows (in thousands):
		30-Jun-14
	Reconciliation to Statement of Cash Flows
	Contract price	$	335,000
	Closing adjustments	4,402
	Gross proceeds from sale (1)	339,402
	Cash sold in the transaction	(95,932		)
	Avista Corp. portion of proceeds held in escrow	(13,567		)
	Gross proceeds from sale of Ecova, net of cash sold (per Statement of Cash Flows)	$	229,903
	Reconciliation of expected net proceeds
	Gross proceeds from sale (1)	$	339,402
	Repayment of long-term borrowings under committed line of credit	(40,000		)
	Payment to option holders and redeemable noncontrolling interests	(20,871		)
	Payment to noncontrolling interests	(54,179		)
	Transaction expenses withheld from proceeds	(5,390		)
	Avista Corp. portion of proceeds held in escrow	(13,567		)
	Net proceeds to Avista Capital at transaction closing	205,395
	Estimated tax payments to be made in 2014	(85,756		)
	Avista Corp. portion of proceeds held in escrow to be received in the future	13,567
	Total net proceeds related to sales transaction	$	133,206
Discontinued Operations Summary of Income Statement Information [Table Text Block]	'
	The following table presents amounts that were included in discontinued operations for the three and nine months ended September 30 (dollars in thousands):
		Three months ended September 30,						Nine months ended September 30,
		2014			2013			2014			2013
	Revenues	$	—		$	46,398		$	87,534		$	133,365
	Gain on sale of Ecova (1)	—			—			161,100			—
	Transaction expenses and accelerated employee benefits (2)	86			—			9,062			—
	Gain on sale of Ecova, net of transaction expenses	(86		)	—			152,038			—
	Income (loss) before income taxes	(86		)	5,540			156,513			10,999
	Income tax expense (benefit)	(31		)	2,092			85,741			4,178
	Net income (loss) from discontinued operations	(55		)	3,448			70,772			6,821
	Net income attributable to noncontrolling interests	—			(485		)	(187		)	(1,292		)
	Net income (loss) from discontinued operations attributable to Avista Corp. shareholders	$	(55	)	$	2,963		$	70,585		$	5,529

Derivatives_And_Risk_Managemen1

Derivatives And Risk Management (Tables)	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedges, Assets [Abstract]	'
Energy Commodity Derivatives	'
	The following table presents the underlying energy commodity derivative volumes as of September 30, 2014 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)
		MWH		MWH			mmBTUs			mmBTUs		MWH	MWH			mmBTUs	mmBTUs
	2014	237		720			12,660			39,325		138	885			1,496	24,288
	2015	508		2,436			13,413			115,860		254	2,935			1,490	89,925
	2016	397		948			2,505			63,173		287	1,634			910	52,713
	2017	397		—			675			2,895		286	—			—	2,895
	2018	397		—			—			—		286	—			—	—
	Thereafter	235		—			—			—		158	—			—	—
	-1	Physical transactions represent commodity transactions where Avista Utilities will take delivery of either electricity or natural gas and financial transactions represent derivative instruments with no physical delivery, such as futures, swaps or options.
Foreign Currency Exchange Contracts	'
	The following table summarizes the foreign currency hedges that the Company has entered into as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,			December 31,
		2014			2013
	Number of contracts	23			23
	Notional amount (in United States dollars)	$	15,734		$	8,631
	Notional amount (in Canadian dollars)	17,326			9,191
Interest Rate Swap Agreements	'
	The following table summarizes the interest rate swaps that the Company has entered into as of September 30, 2014 and December 31, 2013 (dollars in thousands):
	Balance Sheet Date		Number of Contracts	Notional Amount				Mandatory Cash Settlement Date
	September 30, 2014		2	$	50,000			2014
			5	75,000				2015
			5	95,000				2016
			3	45,000				2017
			7	155,000				2018
	December 31, 2013		2	50,000				2014
			2	45,000				2015
			2	40,000				2016
			1	15,000				2017
			4	95,000				2018
Derivative Instruments Summary	'
	The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of September 30, 2014 (in thousands):
				Fair Value
	Derivative		Balance Sheet Location	Gross				Gross			Collateral		Net Asset
				Asset				Liability			Netting		(Liability)
													in Balance
													Sheet
	Foreign currency contracts		Other current liabilities	$	—			$	(280	)	$	—	$	(280	)
	Interest rate contracts		Other current assets	7,106				—			—		7,106
	Interest rate contracts		Other property and investments - net	4,933				(3,786		)	—		1,147
	Interest rate contracts		Other non-current liabilities and deferred credits	1,261				(30,699		)	12,730		(16,708		)
	Commodity contracts (1)		Current utility energy commodity derivative assets	11,371				(8,037		)	—		3,334
	Commodity contracts (1)		Non-current utility energy commodity derivative assets	10,639				(8,946		)	—		1,693
	Commodity contracts (1)		Current utility energy commodity derivative liabilities	21,002				(26,060		)	49		(5,009		)
	Commodity contracts (1)		Other non-current liabilities and deferred credits	10,537				(25,383		)	886		(13,960		)
	Total derivative instruments recorded on the balance sheet			$	66,849			$	(103,191	)	$	13,665	$	(22,677	)
	The following table presents the fair values and locations of derivative instruments recorded on the Condensed Consolidated Balance Sheet as of December 31, 2013 (in thousands):
				Fair Value
	Derivative		Balance Sheet Location	Gross				Gross			Collateral		Net Asset
				Asset				Liability			Netting		(Liability)
													in Balance
													Sheet
	Foreign currency contracts		Other current assets	$	7			$	(6	)	$	—	$	1
	Interest rate contracts		Other current assets	13,968				—			—		13,968
	Interest rate contracts		Other property and investments - net	19,575				—			—		19,575
	Commodity contracts (1)		Current utility energy commodity derivative assets	7,416				(4,394		)	—		3,022
	Commodity contracts (1)		Non-current utility energy commodity derivative assets	7,610				(6,756		)	—		854
	Commodity contracts (1)		Current utility energy commodity derivative liabilities	23,455				(37,306		)	2,976		(10,875		)
	Commodity contracts (1)		Other non-current liabilities and deferred credits	17,101				(41,213		)	5,756		(18,356		)
	Total derivative instruments recorded on the balance sheet			$	89,132			$	(89,675	)	$	8,732	$	8,189
	-1	Avista Corp. had a master netting agreement that governed the transactions of multiple affiliated legal entities under this single master netting agreement. This master netting agreement allowed for cross-commodity netting (i.e. netting physical power, physical natural gas, and financial transactions) and cross-affiliate netting for the parties to the agreement. Avista Corp. performed cross-commodity netting for each legal entity that is a party to the master netting agreement for presentation in the Condensed Consolidated Balance Sheets; however, Avista Corp. did not perform cross-affiliate netting because the Company believed that cross-affiliate netting may not be enforceable. Therefore, the requirements for cross-affiliate netting under ASC 210-20-45 were not applicable for Avista Corp. As of December 31, 2013, all derivatives for each affiliated entity under this master netting agreement were in a net liability position. As such, there was no additional netting which required disclosure for that period. In May 2014, this master netting agreement was terminated and each affiliated legal entity is now under their own separate agreement. As of September 30, 2014, the Company no longer has any agreements where cross-affiliate netting is allowed under the agreement, but not performed by the Company.

Pension_Plans_And_Other_Postre1

Pension Plans And Other Postretirement Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Components of Net Periodic Benefit Cost	'
		Pension Benefits						Other Post-retirement Benefits
		2014			2013			2014			2013
	Three months ended September 30:
	Service cost	$	3,868		$	4,743		$	499		$	971
	Interest cost	6,706			5,978			1,353			1,373
	Expected return on plan assets	(8,110		)	(6,900		)	(472		)	(402		)
	Amortization of prior service cost	6			75			(43		)	(37		)
	Net loss recognition	1,163			3,220			826			1,395
	Net periodic benefit cost	$	3,633		$	7,116		$	2,163		$	3,300
	Nine months ended September 30:
	Service cost	$	12,754		$	14,229		$	1,972		$	3,035
	Interest cost	20,118			17,934			4,059			4,153
	Expected return on plan assets	(24,330		)	(20,700		)	(1,416		)	(1,202		)
	Amortization of prior service cost	18			225			(129		)	(111		)
	Net loss recognition	2,334			9,989			2,001			4,342
	Net periodic benefit cost	$	10,894		$	21,677		$	6,487		$	10,217

Committed_Lines_of_Credit_Tabl

Committed Lines of Credit (Tables)	9 Months Ended
	Sep. 30, 2014
Schedule Of Borrowings Outstanding And Letters Of Credit	'
	Balances outstanding and interest rates of borrowings (excluding letters of credit) under the Company’s revolving committed lines of credit were as follows as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30,			December 31,
		2014			2013
	Borrowings outstanding at end of period	$	35,000		$	171,000
	Letters of credit outstanding at end of period	$	45,614		$	27,434
	Average interest rate on borrowings at end of period	0.92		%	1.02		%
Ecova [Member]	'
Schedule Of Borrowings Outstanding And Letters Of Credit	'
		December 31,
		2013
	Borrowings outstanding at end of period	$	46,000
	Average interest rate on borrowings at end of period	2.17		%

LongTerm_Debt_Tables

Long-Term Debt (Tables)	9 Months Ended
	Sep. 30, 2014
Long-term Debt, Unclassified [Abstract]	'
Schedule of Maturities of Long-term Debt [Table Text Block]	'
	The following table details future capital lease obligations, including interest, under the Snettisham PPA (dollars in thousands):
		2014			2015				2016				2017		2018		Thereafter		Total
	Principal	$	526		$	2,230			$	2,350			$	2,480	$	2,615	$	60,280	$	70,481
	Interest	954			3,690				3,567				3,438		3,305		28,529		43,483
	Total	$	1,480		$	5,920			$	5,917			$	5,918	$	5,920	$	88,809	$	113,964
Long-term Debt Outstanding	'
	Maturity			Interest		September 30,				December 31,
	Year		Description	Rate		2014				2013
	Avista Corp. Secured Long-Term Debt
	2016		First Mortgage Bonds	0.84%		$	90,000			$	90,000
	2018		First Mortgage Bonds	5.95%		250,000				250,000
	2018		Secured Medium-Term Notes	7.39%-7.45%		22,500				22,500
	2019		First Mortgage Bonds	5.45%		90,000				90,000
	2020		First Mortgage Bonds	3.89%		52,000				52,000
	2022		First Mortgage Bonds	5.13%		250,000				250,000
	2023		Secured Medium-Term Notes	7.18%-7.54%		13,500				13,500
	2028		Secured Medium-Term Notes	6.37%		25,000				25,000
	2032		Secured Pollution Control Bonds (1)	-1		66,700				66,700
	2034		Secured Pollution Control Bonds (1)	-1		17,000				17,000
	2035		First Mortgage Bonds	6.25%		150,000				150,000
	2037		First Mortgage Bonds	5.70%		150,000				150,000
	2040		First Mortgage Bonds	5.55%		35,000				35,000
	2041		First Mortgage Bonds	4.45%		85,000				85,000
	2047		First Mortgage Bonds	4.23%		80,000				80,000
			Total Avista Corp. secured long-term debt			1,376,700				1,376,700
	Alaska Electric Light and Power Company Secured Long-Term Debt
	2044		First Mortgage Bonds (2)	4.54%		75,000				—
			Total consolidated secured long-term debt			1,451,700				1,376,700
			Other long-term debt and capital leases			74,754				4,630
			Settled interest rate swaps (3)			(23,118		)		(23,560		)
			Unamortized debt discount			(954		)		(1,287		)
			Total			1,502,382				1,356,483
			Secured Pollution Control Bonds held by Avista Corporation (1)			(83,700		)		(83,700		)
			Current portion of long-term debt and capital leases			(6,471		)		(358		)
			Total long-term debt and capital leases			$	1,412,211			$	1,272,425
	-1	In December 2010, $66.7 million and $17.0 million of the City of Forsyth, Montana Pollution Control Revenue Refunding Bonds (Avista Corporation Colstrip Project) due in 2032 and 2034, respectively, which had been held by Avista Corp. since 2008 and 2009, respectively, were refunded by new bond issues (Series 2010A and Series 2010B). The new bonds were not offered to the public and were purchased by Avista Corp. due to market conditions. The Company expects that at a later date, subject to market conditions, these bonds may be remarketed to unaffiliated investors. So long as Avista Corp. is the holder of these bonds, the bonds will not be reflected as an asset or a liability on Avista Corp.'s Condensed Consolidated Balance Sheets.
	-2	In September 2014, AEL&P issued $75.0 million of 4.54 percent first mortgage bonds due in 2044 to two institutional investors in the private placement market. The first mortgage bonds were issued under and in accordance with the AEL&P Mortgage and Deed of Trust, dated as of July 1, 2014.
	-3	Upon settlement of interest rate swaps, these are recorded as a regulatory asset or liability and included as part of long-term debt above. They are amortized as a component of interest expense over the life of the associated debt and included as a part of the Company's cost of debt calculation for ratemaking purposes.

Fair_Value_Tables

Fair Value (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]	'
Fair Value Inputs, Liabilities, Quantitative Information [Table Text Block]	'
			Fair Value (Net) at
			September 30, 2014				Valuation Technique		Unobservable		Range
									Input
	Power exchange agreement		$	(12,854	)		Surrogate facility		O&M charges		$30.66-$55.56/MWh (1)
							pricing		Escalation factor		3% - 2014 to 2019
									Transaction volumes		310,103 - 397,116 MWhs
	Power option agreement		(362		)		Black-Scholes-		Strike price		$56.20/MWh - 2015
							Merton				$67.81/MWh - 2019
									Delivery volumes		32,472 - 287,147 MWhs
									Volatility rates		0.20 (2)
	Natural gas exchange		(1,471		)		Internally derived		Forward purchase		$3.43 - $3.68/mmBTU
	agreement						weighted average		prices
							cost of gas		Forward sales prices		$4.19 - $4.72/mmBTU
									Purchase volumes		280,000 - 310,000 mmBTUs
									Sales volumes		279,990 - 310,000 mmBTUs
Carrying Value and Estimated Fair Value of Financial Instruments	'
	The following table sets forth the carrying value and estimated fair value of the Company’s financial instruments not reported at estimated fair value on the Condensed Consolidated Balance Sheets as of September 30, 2014 and December 31, 2013 (dollars in thousands):
		September 30, 2014								December 31, 2013
		Carrying				Estimated				Carrying			Estimated
		Value				Fair Value				Value			Fair Value
	Long-term debt (Level 2)	$	951,000			$	1,100,345			$	951,000		$	1,054,512
	Long-term debt (Level 3)	417,000				431,758				342,000			329,581
	Snettisham capital lease obligation (Level 3)	70,481				77,835				—			—
	Nonrecourse long-term debt (Level 3)	5,666				5,756				17,838			18,636
	Long-term debt to affiliated trusts (Level 3)	51,547				38,583				51,547			37,114
Fair Value of Assets And Liabilities Measured on Recurring Basis	'
		Level 1				Level 2				Level 3			Counterparty			Total
													and Cash
													Collateral
													Netting (1)
	30-Sep-14
	Assets:
	Energy commodity derivatives	$	—			$	52,691			$	—		$	(47,664	)	$	5,027
	Level 3 energy commodity derivatives:
	Natural gas exchange agreement	—				—				58			(58		)	—
	Power exchange agreement	—				—				800			(800		)	—
	Interest rate swaps	—				13,300				—			(5,047		)	8,253
	Funds held in trust account of Spokane Energy	1,600				—				—			—			1,600
	Deferred compensation assets:
	Fixed income securities (2)	1,831				—				—			—			1,831
	Equity securities (2)	6,096				—				—			—			6,096
	Total	$	9,527			$	65,991			$	858		$	(53,569	)	$	22,807
	Liabilities:
	Energy commodity derivatives	$	—			$	52,881			$	—		$	(48,599	)	$	4,282
	Level 3 energy commodity derivatives:
	Natural gas exchange agreement	—				—				1,529			(58		)	1,471
	Power exchange agreement	—				—				13,654			(800		)	12,854
	Power option agreement	—				—				362			—			362
	Foreign currency derivatives	—				280				—			—			280
	Interest rate swaps	—				34,485				—			(17,777		)	16,708
	Total	$	—			$	87,646			$	15,545		$	(67,234	)	$	35,957
		Level 1				Level 2				Level 3			Counterparty			Total
													and Cash
													Collateral
													Netting (1)
	31-Dec-13
	Assets:
	Energy commodity derivatives	$	—			$	55,243			$	—		$	(51,367	)	$	3,876
	Level 3 energy commodity derivatives:
	Power exchange agreement	—				—				339			(339		)	—
	Foreign currency derivatives	—				7				—			(6		)	1
	Interest rate swaps	—				33,543				—			—			33,543
	Investments and funds held for clients:
	Money market funds	11,180				—				—			—			11,180
	Securities available for sale:
	U.S. government agency	—				61,078				—			—			61,078
	Municipal	—				3,518				—			—			3,518
	Corporate fixed income – financial	—				3,000				—			—			3,000
	Corporate fixed income – industrial	—				765				—			—			765
	Certificate of deposits	—				1,000				—			—			1,000
	Funds held in trust account of Spokane Energy	1,600				—				—			—			1,600
	Deferred compensation assets:
	Fixed income securities (2)	1,960				—				—			—			1,960
	Equity securities (2)	6,470				—				—			—			6,470
	Total	$	21,210			$	158,154			$	339		$	(51,712	)	$	127,991
	Liabilities:
	Energy commodity derivatives	$	—			$	72,895			$	—		$	(60,099	)	$	12,796
	Level 3 energy commodity derivatives:
	Natural gas exchange agreement	—				—				1,219			—			1,219
	Power exchange agreement	—				—				14,780			(339		)	14,441
	Power option agreement	—				—				775			—			775
	Foreign currency derivatives	—				6				—			(6		)	—
	Total	$	—			$	72,901			$	16,774		$	(60,444	)	$	29,231
	-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 trading securities and are included in other property and investments-net 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				Power Option Agreement			Total
	Three months ended September 30, 2014:
	Balance as of July 1, 2014	$	(2,183	)		$	(7,919	)		$	(605	)	$	(10,707	)
	Total gains or losses (realized/unrealized):
	Included in net income	—				—				—			—
	Included in other comprehensive income	—				—				—			—
	Included in regulatory assets/liabilities (1)	712				(4,935		)		243			(3,980		)
	Purchases	—				—				—			—
	Issuance	—				—				—			—
	Settlements	—				—				—			—
	Transfers to/from other categories	—				—				—			—
	Ending balance as of September 30, 2014	$	(1,471	)		$	(12,854	)		$	(362	)	$	(14,687	)
	Three months ended September 30, 2013:
	Balance as of July 1, 2013	$	(1,022	)		$	(22,179	)		$	(596	)	$	(23,797	)
	Total gains or losses (realized/unrealized):
	Included in net income	—				—				—			—
	Included in other comprehensive income	—				—				—			—
	Included in regulatory assets/liabilities (1)	(170		)		6,135				(165		)	5,800
	Purchases	—				—				—			—
	Issuance	—				—				—			—
	Settlements	(1		)		—				—			(1		)
	Transfers to/from other categories	—				—				—			—
	Ending balance as of September 30, 2013	$	(1,193	)		$	(16,044	)		$	(761	)	$	(17,998	)
	Nine months ended September 30, 2014:
	Balance as of January 1, 2014	$	(1,219	)		$	(14,441	)		$	(775	)	$	(16,435	)
	Total gains or losses (realized/unrealized):
	Included in net income	—				—				—			—
	Included in other comprehensive income	—				—				—			—
	Included in regulatory assets/liabilities (1)	2,796				2,120				413			5,329
	Purchases	—				—				—			—
	Issuance	—				—				—			—
	Settlements	(3,048		)		(533		)		—			(3,581		)
	Transfers to/from other categories	—				—				—			—
	Ending balance as of September 30, 2014	$	(1,471	)		$	(12,854	)		$	(362	)	$	(14,687	)
		Natural Gas Exchange Agreement				Power Exchange Agreement				Power Option Agreement			Total
	Nine months ended September 30, 2013:
	Balance as of January 1, 2013	$	(2,379	)		$	(18,692	)		$	(1,480	)	$	(22,551	)
	Total gains or losses (realized/unrealized):
	Included in net income	—				—				—			—
	Included in other comprehensive income	—				—				—			—
	Included in regulatory assets/liabilities (1)	1,637				(113		)		719			2,243
	Purchases	—				—				—			—
	Issuance	—				—				—			—
	Settlements	(451		)		2,761				—			2,310
	Transfers from other categories	—				—				—			—
	Ending balance as of September 30, 2013	$	(1,193	)		$	(16,044	)		$	(761	)	$	(17,998	)
	-1	The UTC and the IPUC issued accounting orders authorizing Avista Corp. to offset commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment defers the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. The orders provide for Avista Corp. to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the period of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rates cases.

Earnings_Per_Common_Share_Attr1

Earnings Per Common Share Attributable To Avista Corporation (Tables)	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Computations Of Earnings Per Share	'
		Three months ended						Nine months ended
		September 30,						September 30,
		2014			2013			2014		2013
	Numerator:
	Net income from continuing operations attributable to Avista Corp. shareholders	$	10,506		$	8,450		$	89,236	$	73,882
	Net income (loss) from discontinued operations attributable to Avista Corp. shareholders	(55		)	2,963			70,585		5,529
	Subsidiary earnings adjustment for dilutive securities (discontinued operations)	—			(81		)	5		(163		)
	Adjusted net income (loss) from discontinued operations attributable to Avista Corp. shareholders for computation of diluted earnings per common share	$	(55	)	$	2,882		$	70,590	$	5,366
	Denominator:
	Weighted-average number of common shares outstanding-basic	63,934			59,994			61,413		59,933
	Effect of dilutive securities:
	Performance and restricted stock awards	310			38			212		31
	Weighted-average number of common shares outstanding-diluted	64,244			60,032			61,625		59,964
	Earnings per common share attributable to Avista Corp. shareholders, basic:
	Earnings per common share from continuing operations	$	0.16		$	0.14		$	1.45	$	1.23
	Earnings per common share from discontinued operations	$	—		$	0.05		$	1.15	$	0.09
	Total earnings per common share attributable to Avista Corp. shareholders, basic	$	0.16		$	0.19		$	2.6	$	1.32
	Earnings per common share attributable to Avista Corp. shareholders, diluted:
	Earnings per common share from continuing operations	$	0.16		$	0.14		$	1.45	$	1.23
	Earnings per common share from discontinued operations	$	—		$	0.05		$	1.14	$	0.09
	Total earnings per common share attributable to Avista Corp. shareholders, diluted	$	0.16		$	0.19		$	2.59	$	1.32
	There were no shares excluded from the calculation because they were antidilutive.

Information_By_Business_Segmen1

Information By Business Segments (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Information by Business Segments	'
	The following table presents information for each of the Company’s business segments (dollars in thousands):
		Avista		Alaska Electric Light and Power Company		Total Utility		Other			Intersegment			Total
		Utilities									Eliminations
											-1
	For the three months ended September 30, 2014:
	Operating revenues	$	282,555	$	9,157	$	291,712	$	10,296		$	(450	)	$	301,558
	Resource costs	128,591		2,997		131,588		—			—			131,588
	Other operating expenses	69,403		3,106		72,509		10,701			(450		)	82,760
	Depreciation and amortization	32,006		1,288		33,294		154			—			33,448
	Income (loss) from operations	32,048		1,273		33,321		(559		)	—			32,762
	Interest expense (2)	18,247		485		18,732		186			(163		)	18,755
	Income taxes	7,146		329		7,475		(174		)	—			7,301
	Net income (loss) from continuing operations attributable to Avista Corp. shareholders	10,349		511		10,860		(354		)	—			10,506
	Capital expenditures (3)	92,197		1,053		93,250		194			—			93,444
	For the three months ended September 30, 2013:
	Operating revenues	$	278,923	$	—	$	278,923	$	11,004		$	(450	)	$	289,477
	Resource costs	131,136		—		131,136		—			—			131,136
	Other operating expenses	69,596		—		69,596		10,662			(450		)	79,808
	Depreciation and amortization	29,823		—		29,823		171			—			29,994
	Income from operations	29,657		—		29,657		170			—			29,827
	Interest expense (2)	18,837		—		18,837		525			(77		)	19,285
	Income taxes	3,945		—		3,945		(578		)	—			3,367
	Net income (loss) from continuing operations attributable to Avista Corp. shareholders	9,447		—		9,447		(1,074		)	77			8,450
	Capital expenditures (3)	75,368		—		75,368		24			—			75,392
	For the nine months ended September 30, 2014:
	Operating revenues	$	1,023,684	$	9,157	$	1,032,841	$	29,225		$	(1,350	)	$	1,060,716
	Resource costs	478,010		2,997		481,007		—			—			481,007
	Other operating expenses	204,089		3,106		207,195		21,864			(1,350		)	227,709
	Depreciation and amortization	93,912		1,288		95,200		452			—			95,652
	Income from operations	177,653		1,273		178,926		6,909			—			185,835
	Interest expense (2)	55,215		485		55,700		899			(330		)	56,269
	Income taxes	48,068		329		48,397		2,877			—			51,274
	Net income from continuing operations attributable to Avista Corp. shareholders	85,030		511		85,541		3,528			167			89,236
	Capital expenditures (3)	228,711		1,053		229,764		296			—			230,060
		Avista		Alaska Electric Light and Power Company		Total Utility		Other			Intersegment			Total
		Utilities									Eliminations
											-1
	For the nine months ended September 30, 2013:
	Operating revenues	$	1,008,669	$	—	$	1,008,669	$	30,145		$	(1,350	)	$	1,037,464
	Resource costs	487,277		—		487,277		—			—			487,277
	Other operating expenses	200,824		—		200,824		30,322			(1,350		)	229,796
	Depreciation and amortization	86,783		—		86,783		536			—			87,319
	Income (loss) from operations	167,648		—		167,648		(713		)	—			166,935
	Interest expense (2)	56,635		—		56,635		1,801			(230		)	58,206
	Income taxes	43,278		—		43,278		(1,349		)	—			41,929
	Net income (loss) from continuing operations attributable to Avista Corp. shareholders	76,265		—		76,265		(2,613		)	230			73,882
	Capital expenditures (3)	220,712		—		220,712		139			—			220,851
	Total Assets:
	As of September 30, 2014:	$	3,991,330	$	261,402	$	4,252,732	$	83,614		$	—		$	4,336,346
	As of December 31, 2013 (4):	$	3,940,998	$	—	$	3,940,998	$	81,282		$	—		$	4,022,280
	-1	Intersegment eliminations reported as operating revenues and resource costs represent intercompany purchases and sales of electric capacity and energy. Intersegment eliminations reported as interest expense and net income (loss) attributable to Avista Corp. shareholders represent intercompany interest.
	-2	Including interest expense to affiliated trusts.
	-3	The capital expenditures for the other businesses are included as other capital expenditures on the Condensed Consolidated Statements of Cash Flows. The remainder of the balance included in other capital expenditures on the Condensed Consolidated Statements of Cash Flows are related to Ecova.
	-4	The consolidated total assets presented here as of December 31, 2013 exclude total assets at Ecova of $339.6 million.

Summary_Of_Significant_Account3

Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)

3 Months Ended

9 Months Ended

12 Months Ended

12 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Jun. 29, 2014

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Ecova [Member]

Other Intangible Assets [Member]

Other Intangible Assets [Member]

Software and Software Development Costs [Member]

Software and Software Development Costs [Member]

Customer Relationships [Member]

Customer Relationships [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Summary Of Significant Accounting Policies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Maximum Dividends Allowed by Debt Covenants

$441,100,000

'

$441,100,000

'

'

'

'

'

'

'

'

'

Finite-Lived Intangible Asset, Useful Life

'

'

'

'

'

'

'1 year

'10 years

'3 years

'7 years

'2 years

'12 years

Owners percentage interest

'

'

'

'

'

80.20%

'

'

'

'

'

'

Investment Portfolio Percentage, Rated AA-, Aa3 and Higher

'

'

'

'

95.00%

'

'

'

'

'

'

'

Sale and maturity of securities available for sale

0

1,825,000

14,612,000

16,955,000

'

'

'

'

'

'

'

'

Maximum Dividends Allowed by Regulator Approval

$291,000,000

'

$291,000,000

'

'

'

'

'

'

'

'

'

Summary_Of_Significant_Account4

Summary Of Significant Accounting Policies (Utility Taxes) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accounting Policies [Abstract]	'	'	'	'
Utility taxes	$11,716	$10,901	$43,923	$41,045

Summary_Of_Significant_Account5

Summary Of Significant Accounting Policies (Other Income - Net) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accounting Policies [Abstract]	'	'	'	'
Interest income	$154	$124	$678	$620
Interest on regulatory deferrals	59	27	154	48
Equity-related AFUDC	2,189	1,595	6,426	4,341
Net loss on investments	-27	-1,299	118	-1,543
Other income	233	41	887	973
Total	$2,608	$488	$8,263	$4,439

Summary_Of_Significant_Account6

Summary Of Significant Accounting Policies (Materials And Supplies Fuel Stock And Natural Gas Stored) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'	'
Materials and supplies	$31,226	$28,747
Fuel stock	5,170	3,170
Natural gas stored	33,545	13,029
Total	$69,941	$44,946

Summary_Of_Significant_Account7

Summary Of Significant Accounting Policies (Investments And Funds Held For Customers) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Available for Sale Securities Debt Effective Maturity	'	'	'	'	'3 years
Proceeds from Sale of Available-for-sale Securities	$0	$1,825	$14,612	$16,955	'
Cash and Cash Equivalents, Amortized Cost	'	'	'	'	16,147	[1]
Cash And Cash Equivalents Unrealized Gain Loss	'	'	'	'	0
Money market funds	'	'	'	'	16,147
Money market funds, Amortized Cost	'	'	'	'	11,180	[1]
Money Market Funds, Unrealized Gain Loss	'	'	'	'	0
Total securities available for sale, Amortized Cost	'	'	'	'	71,883	[1]
Total securities available for sale, Unrealized Gain (Loss)	'	'	'	'	-2,522
Total securities available for sale, Fair Value	'	'	'	'	69,361
Total investments and funds held for clients, Amortized Cost	'	'	'	'	99,210	[1]
Total investments and funds held for clients, Unrealized Gain (Loss)	'	'	'	'	-2,522
Total investments and funds held for clients, fair value	0	'	0	'	96,688
U.S. Government Agency [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Amortized Cost	'	'	'	'	63,633	[1]
Total securities available for sale, Unrealized Gain (Loss)	'	'	'	'	-2,555
Municipal [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Amortized Cost	'	'	'	'	3,497	[1]
Total securities available for sale, Unrealized Gain (Loss)	'	'	'	'	21
Corporate fixed income - financial [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Amortized Cost	'	'	'	'	3,000	[1]
Total securities available for sale, Unrealized Gain (Loss)	'	'	'	'	0
Corporate fixed income - industrial [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Amortized Cost	'	'	'	'	753	[1]
Total securities available for sale, Unrealized Gain (Loss)	'	'	'	'	12
Certificates of deposits [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Amortized Cost	'	'	'	'	1,000	[1]
Total securities available for sale, Unrealized Gain (Loss)	'	'	'	'	0
Fair Value, Measurements, Recurring [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Money Market Funds, Fair Value	'	'	'	'	11,180
Fair Value, Measurements, Recurring [Member] | U.S. Government Agency [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	61,078
Fair Value, Measurements, Recurring [Member] | Municipal [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	3,518
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - financial [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	3,000
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - industrial [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	765
Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	1,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Money Market Funds, Fair Value	'	'	'	'	11,180
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | U.S. Government Agency [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	61,078
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Municipal [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	3,518
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate fixed income - financial [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	3,000
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate fixed income - industrial [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	765
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member]	'	'	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'	'	'
Total securities available for sale, Fair Value	'	'	'	'	$1,000
[1]	(1) Amortized cost represents the original purchase price of the investments, plus or minus any amortized purchase premiums or accreted purchase discounts.

Summary_Of_Significant_Account8

Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Disposition of Available-for-Sale Securities) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Disposition of Available for Sale Securities [Abstract]	'	'	'	'
Proceeds from Sale of Available-for-sale Securities	$0	$1,825	$14,612	$16,955
Available-for-sale Securities, Gross Realized Gains	0	2	3	20
Available-for-sale Securities, Gross Realized Losses	$0	$0	($735)	$0

Summary_Of_Significant_Account9

Summary Of Significant Accounting Policies (Contractual Maturities Of Securities Available For Sale) (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]	'
Due within 1 year	$5,382
After 1 but within 5 years	12,745
After 5 but within 10 years	48,310
After 10 years	2,924
Total securities available for sale, Fair Value	$69,361

Recovered_Sheet1

Summary Of Significant Accounting Policies (Goodwill) (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014
Goodwill, Purchase Accounting Adjustments	$112
Balance at beginning	76,257
Balance at ending	55,877
Goodwill, Written off Related to Sale of Business Unit	-71,123
Goodwill, Acquired During Period	50,631
Ecova [Member]	'
Goodwill, Purchase Accounting Adjustments	112
Balance at beginning	71,011
Balance at ending	0
Goodwill, Written off Related to Sale of Business Unit	-71,123
Goodwill, Acquired During Period	0
Alaska Electric Light & Power [Member]	'
Goodwill, Purchase Accounting Adjustments	0
Balance at beginning	0
Balance at ending	50,631
Goodwill, Written off Related to Sale of Business Unit	0
Goodwill, Acquired During Period	50,631
Other Business Segment [Member]	'
Goodwill, Purchase Accounting Adjustments	0
Balance at beginning	12,979
Balance at ending	12,979
Goodwill, Written off Related to Sale of Business Unit	0
Goodwill, Acquired During Period	0
Accumulated Impairment Losses [Member]	'
Goodwill, Purchase Accounting Adjustments	0
Balance at beginning	-7,733
Balance at ending	-7,733
Goodwill, Written off Related to Sale of Business Unit	0
Goodwill, Acquired During Period	$0

Recovered_Sheet2

Summary Of Significant Accounting Policies (Other Intangible Amortization) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accounting Policies [Abstract]	'	'	'	'
Intangible asset amortization	$0	$2,765	$5,898	$8,442

Recovered_Sheet3

Summary Of Significant Accounting Policies (Accumulated Amortization Of Other Intangibles) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
In Thousands, unless otherwise specified			Ecova [Member]	Ecova [Member]	Other Intangible Assets [Member]	Customer Relationships [Member]	Software and Software Development Costs [Member]	Minimum [Member]	Minimum [Member]	Minimum [Member]
								Other Intangible Assets [Member]	Customer Relationships [Member]	Software and Software Development Costs [Member]
Finite-Lived Intangible Assets [Line Items]	'	'	'	'	'	'	'	'	'	'
Finite-Lived Intangible Asset, Useful Life	'	'	'	'	'	'	'	'1 year	'2 years	'3 years
Client relationships	'	$33,562	'	'	'	'	'	'	'	'
Software development costs	'	39,327	'	'	'	'	'	'	'	'
Other	'	3,321	'	'	'	'	'	'	'	'
Total intangible assets	'	76,210	'	'	'	'	'	'	'	'
Total accumulated amortization	0	-36,634	'	'	-2,437	-12,336	-21,861	'	'	'
Total intangible assets - net	$0	$39,576	$0	$39,576	'	'	'	'	'	'

Recovered_Sheet4

Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Accumulated Other Comprehensive Loss) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Accumulated Other Comprehensive Income (Loss) [Line Items]	'		'
Accumulated Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities, Tax	$0		($936)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans Net Unamortized (Gain) Loss, Tax	-2,099		-2,280
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	-3,898		-4,233
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	0	[1]	-1,586
Accumulated other comprehensive loss	($3,898)		($5,819)
[1]	(1)This entire balance was related to Ecova, which was disposed of as of June 30, 2014.

Recovered_Sheet5

Summary Of Significant Accounting Policies (Reclassifications Out of Accumulated Other Comprehensive Loss) (Details) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]	'		'		'		'
Income (loss) before income taxes	$86		($5,540)		($156,513)		($10,999)
Income tax expense (benefit)	-31		2,092		85,741		4,178
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	55		-3,448		-70,772		-6,821
Tax benefit (expense) (a)	-7,301		-3,367		-51,274		-41,929
Net income	10,471		11,931		160,034		80,762
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]	'		'		'		'
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]	'		'		'		'
Other Comprehensive Income Loss Reclassification Adjustment From AOCI For Realized Losses on Sale of Securities Before Tax	0		0		-735	[1]	0	[1]
Income (loss) before income taxes	0		2		-732		20
Income tax expense (benefit)	0		-1		272	[1]	-8	[1]
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0		1		-460		12
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	0		2		3	[1]	20	[1]
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]	'		'		'		'
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]	'		'		'		'
Total before tax	-172		-283		-516		-848
Tax benefit (expense) (a)	60		99		181		297
Net income	-112		-184		-335		-551
Amortization of net loss	-1,951	[2]	-4,891	[2]	-5,855	[2]	-14,673	[2]
Adjustment due to effects of regulation	$1,779	[2]	$4,608	[2]	$5,339	[2]	$13,825	[2]
[1]	These amounts were included as part of net income from discontinued operations for all periods presented (see Note 5 for additional details).
[2]	These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 7 for additional details).

Recovered_Sheet6

Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Appropriated Retained Earnings) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Appropriated Retained Earnings [Abstract]	'	'
Retained Earnings, Appropriated	$14,270	$9,714

Recovered_Sheet7

Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Stock Repurchase Program) (Details) (USD $)	1 Months Ended			3 Months Ended		4 Months Ended
In Millions, except Share data, unless otherwise specified	Sep. 30, 2014	Aug. 31, 2014	Jul. 31, 2014	Sep. 30, 2014	Jun. 13, 2014	Oct. 31, 2014
						Subsequent Event [Member]
Schedule of Common Stock Repurchases [Line Items]	'	'	'	'	'	'
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	2,076,000	2,781,000	3,708,000	2,076,000	'	'
Stock Repurchased Total Cost	'	'	'	'	'	$79.90
Stock Repurchased During Period, Shares	705,000	927,000	292,000	1,924,000	'	2,529,615
Stock Repurchased, Average Cost per Share	$31.67	$31.50	$32.30	$31.68	'	$31.57
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	'	'	'	'	4,000,000	'

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
	MW
Lancaster Power Purchase Agreement [Member]	'
Evaluated Power Capacity	270
Future contractual obligation	$281
Palouse Wind Power Purchase Agreement [Member]	'
Evaluated Power Capacity	105
Expected power production, in megawatts	40
Future contractual obligation	$591
Minimum [Member] | Lancaster Power Purchase Agreement [Member]	'
Minimum estimated life of plant, in years	'15 years
Maximum [Member] | Lancaster Power Purchase Agreement [Member]	'
Minimum estimated life of plant, in years	'25 years

Business_Acquisitions_Details

Business Acquisitions (Details) (USD $)

3 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

15 Months Ended

9 Months Ended

15 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Jul. 01, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Jul. 01, 2014

Sep. 30, 2014

Jul. 01, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

MW

Alaska Energy Resources Company [Member]

Alaska Energy Resources Company [Member]

Alaska Energy Resources Company [Member]

Alaska Energy Resources Company [Member]

Alaska Energy Resources Company [Member]

Alaska Energy Resources Company [Member]

Alaska Energy Resources Company [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Power purchase agreement [Member]

Hydroelectric Production [Member]

Fossil Fuel Plant [Member]

AEL&P Hydroelectric Production [Member]

Acquisition-related Costs [Member]

D

employee

employee

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Energy Resources Company [Member]

MW

MW

MW

MW

generating_facilities

Business Acquisition [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Electric Generating Facilities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

'

Business Acquisition, Share Price

'

'

'

'

'

'

'

'

'

'

$33.35

'

'

'

'

'

'

'

'

Number of Customers

'

'

'

'

'

'

'

'

'

'

'

16,000

'

'

'

'

'

'

'

Operating revenues

$301,558,000

$289,477,000

$1,060,716,000

$1,037,464,000

'

$9,224,000

$9,309,000

$35,319,000

$31,243,000

'

'

'

'

'

'

'

'

'

'

Total Rate Base

'

'

'

'

'

'

'

'

'

'

'

'

'

109,000,000

'

'

'

'

'

Entity Number of Employees

'

'

'

'

'

'

'

'

'

'

'

'

60

'

'

'

'

'

'

Peak electric usage

'

'

68

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Evaluated Power Capacity

'

'

'

'

'

'

'

'

'

'

'

'

'

'

78

102.7

93.9

24.7

'

Business Acquisition, Equity Interest Issued or Issuable, Number of Shares

'

'

'

'

4,500,014

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Business Combination Equity Consideration Share Price

'

'

'

'

'

'

'

'

'

'

$32.46

'

'

'

'

'

'

'

'

Business Combination Number of Trading Days to Price Equity Consideration Share Price

'

'

10

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Merger Consideration - Total

'

'

'

'

'

'

'

'

'

'

170,000,000

'

'

'

'

'

'

'

'

Representative Reimbursement Amount

'

'

'

'

'

'

'

4,697,000

'

'

'

'

'

'

'

'

'

'

'

Business Combination, Acquisition Related Costs

'

'

'

'

'

'

'

'

'

2,900,000

'

'

'

'

'

'

'

'

400,000

Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents

'

'

'

'

'

'

'

'

'

'

19,704,000

'

'

'

'

'

'

'

'

Business Acquisition Recognized Identifiable Assets Acquired and Liabilities Assumed Current and Long-Term Debt

'

'

'

'

'

'

'

'

'

'

38,832,000

'

'

'

'

'

'

'

'

Business Acquisition Contract Price Closing Adjustments

'

'

'

'

'

'

'

'

'

'

104,000

'

'

'

'

'

'

'

'

Business Acquisition Adjusted Contract Price

'

'

'

'

'

'

'

'

'

'

150,768,000

'

'

'

'

'

'

'

'

Business Combination, Consideration Transferred

'

'

'

'

$154,772,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Business_Acquisitions_Contract

Business Acquisitions Contract Price and Fair Value of Consideration Transferred (Details) (Alaska Energy Resources Company [Member], USD $)	0 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Jul. 01, 2014	Sep. 30, 2014	Jul. 01, 2014
Alaska Energy Resources Company [Member]	'	'	'
Business Acquisition [Line Items]	'	'	'
Merger Consideration - Total	'	'	$170,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	'	'	19,704
Business Acquisition Recognized Identifiable Assets Acquired and Liabilities Assumed Current and Long-Term Debt	'	'	-38,832
Business Acquisition Contract Price Closing Adjustments	'	'	-104
Business Acquisition Adjusted Contract Price	'	'	150,768
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	150,075	'	'
Payments to Acquire Businesses, Gross	'	4,697	'
Business Combination, Consideration Transferred	$154,772	'	'

Business_Acquisitions_Assets_A

Business Acquisitions Assets Acquired Liabilities Assumed (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Jul. 01, 2014	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014
In Thousands, unless otherwise specified			Alaska Energy Resources Company [Member]	Alaska Electric Light & Power [Member]	Alaska Electric Light & Power [Member]	AEL&P Hydroelectric Production [Member]
						Alaska Electric Light & Power [Member]
						generating_facilities
Business Acquisition [Line Items]	'	'	'	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	'	'	$19,704	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	'	'	3,851	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	'	'	3,928	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory	'	'	2,017	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	'	'	999	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	'	'	26,571	'	'	'
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Public Utilities Property Plant and Equipment Plant in Service	'	'	113,964	'	'	'
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed Capital Lease Assets	'	'	71,007	'	'	'
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Public Utilities Property Plant and Equipment, Construction Work in Progress	'	'	3,440	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	'	'	188,411	'	'	'
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Noncurrent Non-Utility Property	'	'	6,660	'	'	'
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed Electric Plant Held for Future Use	'	'	3,711	'	'	'
Goodwill	55,877	76,257	50,631	50,631	0	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	'	'	5,368	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	'	'	13,138	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets	'	'	66,370	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	'	'	281,352	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	'	'	700	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-term Debt	'	'	3,773	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	'	'	2,902	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	'	'	7,375	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	'	'	37,227	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Capital Lease Obligation	'	'	68,840	'	'	'
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	'	'	126,580	'	'	'
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	'	'	$154,772	'	'	'
Number of Electric Generating Facilities	'	'	'	'	'	4

Business_Acquisitions_Pro_Form

Business Acquisitions Pro Forma Operating Results (Details) (USD $)	3 Months Ended		9 Months Ended		15 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014
Business Acquisition [Line Items]	'	'	'	'	'
Revenues Excluding Acquired Entity	$292,334,000	$289,477,000	$1,051,492,000	$1,037,464,000	'
Supplemental Pro Forma Revenues	301,558,000	289,477,000	1,060,716,000	1,037,464,000	'
Business Acquisition, Pro Forma Revenue	301,558,000	298,786,000	1,086,811,000	1,068,707,000	'
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	9,224,000	0	9,224,000	0	'
Income (Loss) from Continuing Operations Attributable to Parent	9,982,000	8,450,000	88,712,000	73,882,000	'
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	-55,000	2,963,000	70,585,000	5,529,000	'
Net income attributable to Avista Corporation shareholders	10,451,000	11,413,000	159,821,000	79,411,000	'
Business Acquisition, Pro Forma Net Income (Loss)	10,852,000	11,678,000	166,286,000	85,217,000	'
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual	524,000	0	524,000	0	'
Weighted Average Basic Shares Outstanding, Pro Forma	63,934	64,494	64,413	64,433	'
Pro Forma Weighted Average Shares Outstanding, Diluted	64,244	64,532	64,625	64,464	'
Business Acquisition, Pro Forma Earnings Per Share, Basic	$0.17	$0.18	$2.58	$1.32	'
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$0.17	$0.18	$2.57	$1.32	'
Alaska Energy Resources Company [Member]	'	'	'	'	'
Business Acquisition [Line Items]	'	'	'	'	'
Gain (Loss) on Disposition of Assets	'	'	'	2,300,000	'
Supplemental Pro Forma Revenues	9,224,000	9,309,000	35,319,000	31,243,000	'
Business Combination, Acquisition Related Costs	'	'	'	'	2,900,000
Net income attributable to Avista Corporation shareholders	524,000	199,000	6,151,000	7,634,000	'
Acquisition-related Costs [Member] | Alaska Energy Resources Company [Member]	'	'	'	'	'
Business Acquisition [Line Items]	'	'	'	'	'
Business Combination, Acquisition Related Costs	$401,000	$66,000	$838,000	($1,828,000)	'

Discontinued_Operations_Summar

Discontinued Operations Summary of Cash Proceeds from Sale of Discontinued Operations (Details) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014
	M
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'
Contract price	$335,000,000	'	'
Closing adjustments	4,402,000	'	'
Gross proceeds from sale (1)	339,402,000	'	'
Cash sold in the transaction	-95,932,000	'	-95,932,000
Avista Corp. portion of proceeds held in escrow	-13,567,000	'	'
Proceeds from Divestiture of Businesses, Net of Cash Divested	229,903,000	0	'
Repayment of long-term borrowings under committed line of credit	-46,000,000	-7,000,000	'
Payment to option holders and redeemable noncontrolling interests	-20,871,000	0	'
Payments to Noncontrolling Interests	-54,179,000	0	'
Transaction expenses withheld from proceeds	-5,390,000	'	'
Net proceeds to Avista Capital at transaction closing	205,395,000	'	'
Business Disposition Estimated Tax Payments	-85,756,000	'	'
Total net proceeds related to sales transaction	133,206,000	'	'
Number of Months Receivable Held in Escrow	15	'	'
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	68,000,000	'	'
Ecova [Member]	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'
Repayment of long-term borrowings under committed line of credit	-40,000,000	'	'
Indemnification Agreement [Member]	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'
Escrow Receivable	16,750,000	'	'
Escrow Percentage of Contract Price	5.00%	'	'
Working Capital Escrow Adjustment [Member]	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'
Escrow Receivable	$1,500,000	'	'

Discontinued_Operations_Summar1

Discontinued Operations Summary of Assets and Liabilities (Details) (USD $)	Sep. 30, 2014	Jun. 30, 2014
In Thousands, unless otherwise specified
Discontinued Operations Summary of Assets and Liabilities [Abstract]	'	'
Disposal Group Including Discontinued Operation Allowance for Doubtful Accounts	$410	'
Cash sold in the transaction	95,932	95,932
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net	'	32,070
Investments and funds held for clients	'	114,598
Income taxes receivable	'	2,548
Other current assets	'	8,908
Total current assets	'	254,056
Goodwill	'	71,123
Intangible assets-net of accumulated amortization of $42,266	'	37,185
Other property and investments-net	'	4,656
Total other non-current assets	'	112,964
Total assets	'	367,020
Accounts payable	'	72,453
Client fund obligations	'	115,333
Current portion of long-term debt	'	67
Other current liabilities	'	35,329
Total current liabilities	'	223,182
Long-term borrowings under committed line of credit	'	40,000
Other non-current liabilities	'	2,117
Total liabilities	'	265,299
Disposal Group Including Discontinued Operation Accumulated Amortization	$42,266	'

Discontinued_Operations_Summar2

Discontinued Operations Summary of Income Statement Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	'	'	$68,000,000	'
Contract price	'	'	335,000,000	'
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	-55,000	2,963,000	70,585,000	5,529,000
Transaction expenses withheld from proceeds	'	'	5,390,000	'
Revenues	0	46,398,000	87,534,000	133,365,000
Gain on sale of Ecova (1)	0	0	161,100,000	0
Transaction expenses and accelerated employee benefits (2)	'	'	11,000,000	'
Gain on sale of Ecova, net of transaction expenses	-86,000	0	152,038,000	0
Income (loss) before income taxes	-86,000	5,540,000	156,513,000	10,999,000
Income tax expense (benefit)	-31,000	2,092,000	85,741,000	4,178,000
Net income (loss) from discontinued operations	-55,000	3,448,000	70,772,000	6,821,000
Net income attributable to noncontrolling interests	-20,000	-518,000	-213,000	-1,351,000
Ecova [Member]	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'
Transaction expenses and accelerated employee benefits (2)	86,000	0	9,062,000	0
Net income attributable to noncontrolling interests	$0	($485,000)	($187,000)	($1,292,000)

Derivatives_And_Risk_Managemen2

Derivatives And Risk Management (Narrative) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Derivative [Line Items]	'	'
Secured Debt	$1,451,700,000	$1,376,700,000
Cash deposited as collateral	7,400,000	26,100,000
Derivative, Fair Value, Amount Offset Against Collateral, Net	13,665,000	8,732,000
Liability position at aggregate fair value	4,300,000	13,300,000
Collateral agreements	5,900,000	12,600,000
Commodity Contracts [Member]	'	'
Derivative [Line Items]	'	'
Letters of credit outstanding	38,500,000	20,300,000
Interest Rate Swap [Member]	'	'
Derivative [Line Items]	'	'
Cash deposited as collateral	$12,700,000	'

Derivatives_And_Risk_Managemen3

Derivatives And Risk Management (Energy Commodity Derivatives) (Details)	9 Months Ended
	Sep. 30, 2014
	frequency
Sales [Member] | Physical [Member] | Electric Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	138,000	[1]
2015	254,000	[1]
2016	287,000	[1]
2017	286,000	[1]
2018	286,000	[1]
Thereafter	158,000	[1]
Sales [Member] | Physical [Member] | Gas Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	1,496,000	[1]
2015	1,490,000	[1]
2016	910,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Sales [Member] | Financial [Member] | Electric Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	885,000	[1]
2015	2,935,000	[1]
2016	1,634,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Sales [Member] | Financial [Member] | Gas Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	24,288,000	[1]
2015	89,925,000	[1]
2016	52,713,000	[1]
2017	2,895,000	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Physical [Member] | Electric Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	237,000	[1]
2015	508,000	[1]
2016	397,000	[1]
2017	397,000	[1]
2018	397,000	[1]
Thereafter	235,000	[1]
Purchase [Member] | Physical [Member] | Gas Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	12,660,000	[1]
2015	13,413,000	[1]
2016	2,505,000	[1]
2017	675,000	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Financial [Member] | Electric Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	720,000	[1]
2015	2,436,000	[1]
2016	948,000	[1]
2017	0	[1]
2018	0	[1]
Thereafter	0	[1]
Purchase [Member] | Financial [Member] | Gas Derivative [Member]	'
Energy Commodity Derivative Volumes [Line Items]	'
2014	39,325,000	[1]
2015	115,860,000	[1]
2016	63,173,000	[1]
2017	2,895,000	[1]
2018	0	[1]
Thereafter	0	[1]
[1]	Physical transactions represent commodity transactions where Avista Utilities will take delivery of either electricity or natural gas and financial transactions represent derivative instruments with no physical delivery, such as futures, swaps or options.

Derivatives_And_Risk_Managemen4

Derivatives And Risk Management (Interest Rate Swap Agreements) (Details) (USD $)

9 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

1 Months Ended

9 Months Ended

12 Months Ended

1 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Oct. 31, 2014

Sep. 30, 2014

Dec. 31, 2013

Oct. 31, 2014

Oct. 31, 2014

Oct. 31, 2014

Sep. 30, 2014

Dec. 31, 2013

Oct. 31, 2014

2014 [Member]

2014 [Member]

2015 [Member]

2015 [Member]

2016 [Member]

2016 [Member]

2017 [Member]

2017 [Member]

Two Thousand Eighteen [Member]

Two Thousand Eighteen [Member]

Two Thousand Eighteen [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Avista Corporation [Member]

Avista Corporation [Member]

2044 [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

2014 [Member]

Two Thousand Eighteen [Member]

First Mortgage Bonds [Member]

Caontracts

Caontracts

Caontracts

Caontracts

Caontracts

Caontracts

Caontracts

Caontracts

Caontracts

Caontracts

Interest Rate Swap Agreements [Member]

Interest Rate Swap Agreements [Member]

Avista Corporation [Member]

Caontracts

Caontracts

Subsequent Event [Member]

Derivatives, Fair Value [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of contracts

'

'

'

2

2

5

2

5

2

3

1

'

7

4

'

2

9

'

'

'

Number of Interest Rate Derivatives Entered into Subsequent to Period End

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

'

'

'

Derivative, Notional Amount

'

'

'

$50,000,000

$50,000,000

$75,000,000

$45,000,000

$95,000,000

$40,000,000

$45,000,000

$15,000,000

'

$155,000,000

$95,000,000

'

'

$205,000,000

'

'

'

Derivative, Maturity Date

'

'

'

31-Dec-14

31-Dec-14

31-Dec-15

31-Dec-15

31-Dec-16

31-Dec-16

31-Dec-17

31-Dec-17

30-Jun-18

31-Dec-18

31-Dec-18

'

'

'

'

'

'

Payments for (Proceeds from) Derivative Instrument, Financing Activities

0

2,901,000

'

'

'

'

'

'

'

'

'

'

'

'

5,400,000

'

'

'

'

'

Secured Debt

1,451,700,000

'

1,376,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,376,700,000

1,376,700,000

60,000,000

Derivative Notional Amount Subsequent to Period End

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$50,000,000

'

'

'

Derivatives_And_Risk_Managemen5

Derivatives And Risk Management (Derivative Instruments Summary) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	$66,849,000		$89,132,000
Gross Liability	-103,191,000		-89,675,000
Collateral Netting	13,665,000		8,732,000
Net Asset (Liability) in Balance Sheet	-22,677,000		8,189,000
Other Current Liabilities [Member] | Foreign Exchange Contract [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	0		'
Gross Liability	-280,000		'
Collateral Netting	0		'
Net Asset (Liability) in Balance Sheet	-280,000		'
Other Current Liabilities [Member] | Foreign Exchange Contract [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	'		7,000
Gross Liability	'		-6,000
Collateral Netting	'		0
Net Asset (Liability) in Balance Sheet	'		1,000
Other Current Liabilities [Member] | Interest Rate Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	7,106,000		13,968,000
Gross Liability	0		0
Collateral Netting	0		0
Net Asset (Liability) in Balance Sheet	7,106,000		13,968,000
Other Property and Investments-Net [Member] | Interest Rate Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	4,933,000		19,575,000
Gross Liability	-3,786,000		0
Collateral Netting	0		0
Net Asset (Liability) in Balance Sheet	1,147,000		19,575,000
Current Utility Energy Commodity Derivative Assets [Member] | Commodity Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	11,371,000	[1]	7,416,000	[1]
Gross Liability	-8,037,000	[1]	-4,394,000	[1]
Collateral Netting	0	[1]	0	[1]
Net Asset (Liability) in Balance Sheet	3,334,000	[1]	3,022,000	[1]
Non-Current Utility Energy Commodity Derivative Assets [Member] | Commodity Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	10,639,000	[1]	7,610,000	[1]
Gross Liability	-8,946,000	[1]	-6,756,000	[1]
Collateral Netting	0	[1]	0	[1]
Net Asset (Liability) in Balance Sheet	1,693,000	[1]	854,000	[1]
Current Utility Energy Commodity Derivative Liabilities [Member] | Commodity Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	21,002,000	[1]	23,455,000	[1]
Gross Liability	-26,060,000	[1]	-37,306,000	[1]
Collateral Netting	49,000	[1]	2,976,000	[1]
Net Asset (Liability) in Balance Sheet	-5,009,000	[1]	-10,875,000	[1]
Other Noncurrent Liabilities [Member] | Interest Rate Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	1,261,000		'
Gross Liability	-30,699,000		'
Collateral Netting	12,730,000		'
Net Asset (Liability) in Balance Sheet	-16,708,000		'
Other Noncurrent Liabilities [Member] | Commodity Contracts [Member]	'		'
Derivatives, Fair Value [Line Items]	'		'
Gross Asset	10,537,000	[1]	17,101,000	[1]
Gross Liability	-25,383,000	[1]	-41,213,000	[1]
Collateral Netting	886,000	[1]	5,756,000	[1]
Net Asset (Liability) in Balance Sheet	($13,960,000)	[1]	($18,356,000)	[1]
[1]	Avista Corp. had a master netting agreement that governed the transactions of multiple affiliated legal entities under this single master netting agreement. This master netting agreement allowed for cross-commodity netting (i.e. netting physical power, physical natural gas, and financial transactions) and cross-affiliate netting for the parties to the agreement. Avista Corp. performed cross-commodity netting for each legal entity that is a party to the master netting agreement for presentation in the Condensed Consolidated Balance Sheets; however, Avista Corp. did not perform cross-affiliate netting because the Company believed that cross-affiliate netting may not be enforceable. Therefore, the requirements for cross-affiliate netting under ASC 210-20-45 were not applicable for Avista Corp. As of December 31, 2013, all derivatives for each affiliated entity under this master netting agreement were in a net liability position. As such, there was no additional netting which required disclosure for that period. In May 2014, this master netting agreement was terminated and each affiliated legal entity is now under their own separate agreement. As of September 30, 2014, the Company no longer has any agreements where cross-affiliate netting is allowed under the agreement, but not performed by the Company.

Derivatives_And_Risk_Managemen6

Derivatives And Risk Management Derivatives and Risk Management (Foreign Currency Exchange Contracts) (Details)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Dec. 31, 2013
	derivative_contracts	derivative_contracts	Foreign Exchange Contract [Member]	Foreign Exchange Contract [Member]	Foreign Exchange Contract [Member]	Foreign Exchange Contract [Member]
			United States of America, Dollars	United States of America, Dollars	Canada, Dollars	Canada, Dollars
			USD ($)	USD ($)	CAD	CAD
Schedule of Foreign Currency Derivative Contracts Outstanding [Line Items]	'	'	'	'	'	'
Number Of Days Canadian Currency Prices Are Settled With U.S. Dollars	'60 days	'	'	'	'	'
Number of Foreign Currency Derivatives Held	23	23	'	'	'	'
Derivative, Notional Amount	'	'	$15,734	$8,631	17,326	9,191

Pension_Plans_And_Other_Postre2

Pension Plans And Other Postretirement Benefit Plans (Narrative) (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Pension Contributions	$32,000,000	$44,000,000	'
Contributions to defined benefit pension plan	($32,000,000)	'	($44,300,000)

Pension_Plans_And_Other_Postre3

Pension Plans And Other Postretirement Benefit Plans (Components Of Net Periodic Benefit Cost) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Pension Benefits [Member]	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Service cost	$3,868	$4,743	$12,754	$14,229
Interest cost	6,706	5,978	20,118	17,934
Expected return on plan assets	-8,110	-6,900	-24,330	-20,700
Amortization of prior service cost	6	75	18	225
Net loss recognition	1,163	3,220	2,334	9,989
Net periodic benefit cost	3,633	7,116	10,894	21,677
Other Post-Retirement Benefits [Member]	'	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'
Service cost	499	971	1,972	3,035
Interest cost	1,353	1,373	4,059	4,153
Expected return on plan assets	-472	-402	-1,416	-1,202
Amortization of prior service cost	-43	-37	-129	-111
Net loss recognition	826	1,395	2,001	4,342
Net periodic benefit cost	$2,163	$3,300	$6,487	$10,217

Committed_Lines_of_Credit_Deta

Committed Lines of Credit (Details) (USD $)	9 Months Ended				9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2013	Feb. 28, 2011	Sep. 30, 2014	Jul. 01, 2014	Jul. 31, 2012	Sep. 30, 2014
	Avista Corporation [Member]	Avista Corporation [Member]	Ecova [Member]	Line of Credit [Member]	Line of Credit [Member]	Line of Credit [Member]	Line of Credit [Member]	Minimum [Member]
				Avista Corporation [Member]	Alaska Electric Light & Power [Member]	Alaska Electric Light & Power [Member]	Ecova [Member]	Line of Credit [Member]
								Alaska Electric Light & Power [Member]
Short-term Debt [Line Items]	'	'	'	'	'	'	'	'
Line of Credit Facility, Maximum Borrowing Capacity	'	'	'	$400,000,000	'	$14,500,000	$125,000,000	'
Line Of Credit Facility Percentage Below Prime	'	'	'	'	0.25%	'	'	'
Line of Credit Facility, Commitment Fee Percentage	'	'	'	'	0.45%	'	'	'
Line of Credit Facility, Covenant Terms	'0.65	'	'	'	'	'	'	'
Balance outstanding at end of period	35,000,000	171,000,000	46,000,000	'	'	'	'	'
Letters of credit outstanding at end of period	$45,614,000	$27,434,000	'	'	'	'	'	'
Average interest rate at end of period	0.92%	1.02%	2.17%	'	'	'	'	4.00%

LongTerm_Debt_Narrative_Detail

Long-Term Debt (Narrative) (Details) (USD $)

0 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

Dec. 31, 1998

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Aug. 18, 1998

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Aug. 18, 1998

Aug. 18, 1998

2032 [Member]

2034 [Member]

AIDEA [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Power purchase agreement [Member]

Capital Lease Interest [Member]

Capital Lease Amortization [Member]

Minimum [Member]

Maximum [Member]

Secured Debt [Member]

Secured Debt [Member]

Capital Lease Obligations [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

AIDEA [Member]

AIDEA [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Long Term Revenue Bonds

'

'

'

'

'

'

'

'

$100,000,000

'

'

'

'

'

'

'

'

'

'

'

Capital Lease Obligations

'

'

'

'

'

'

'

'

'

'

70,481,000

'

'

'

'

'

'

'

'

'

Long-term Pollution Control Bond, Noncurrent

'

-83,700,000

[1]

'

-83,700,000

[1]

'

-83,700,000

[1]

66,700,000

17,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Debt instrument, interest rate, stated percentage

8.45%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount borrowed to acquire a long-term fixed rate electric capacity contract

145,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Funds held in trust account which are used to secure long-term debt

'

1,600,000

'

1,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Leased Assets, Gross

'

'

'

'

'

'

'

'

'

71,000,000

'

'

'

'

'

'

'

'

'

'

Capital Leases Assets Accumulated Depreciation

'

'

'

'

'

'

'

'

'

-900,000

'

'

'

'

'

'

'

'

'

'

Utilities Operating Expense, Products and Services

'

131,588,000

131,136,000

481,007,000

487,277,000

'

'

'

'

'

'

2,997,000

0

2,997,000

0

10,600,000

1,000,000

900,000

'

'

Long Term Revenue Bonds Stated Interest Rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4.85%

6.00%

Capital Lease Obligations Annual Minimum Payments of Principal and Interest

'

'

'

'

'

'

'

'

'

'

$5,900,000

'

'

'

'

'

'

'

'

'

[1]

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

LongTerm_Debt_Schedule_Of_Long

Long-Term Debt (Schedule Of Long-Term Debt Instruments) (Details) (USD $)

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

9 Months Ended

1 Months Ended

In Thousands, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Dec. 31, 1998

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Oct. 31, 2014

Oct. 31, 2014

2018, 7.39% - 7.45% [Member]

2023, 7.18% - 7.54% [Member]

2032 [Member]

2034 [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Avista Corporation [Member]

Alaska Electric Light & Power [Member]

Alaska Electric Light & Power [Member]

Subsequent Event [Member]

Subsequent Event [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

2018, 5.95% [Member]

2018, 5.95% [Member]

2018, 7.39% - 7.45% [Member]

2018, 7.39% - 7.45% [Member]

2019 [Member]

2019 [Member]

2020 [Member]

2020 [Member]

2022 [Member]

2022 [Member]

2023, 7.18% - 7.54% [Member]

2023, 7.18% - 7.54% [Member]

2028 [Member]

2028 [Member]

2032 [Member]

2032 [Member]

2034 [Member]

2034 [Member]

2035 [Member]

2035 [Member]

2037 [Member]

2037 [Member]

2040 [Member]

2040 [Member]

2041 [Member]

2041 [Member]

2047 [Member]

2047 [Member]

2016 [Member]

2016 [Member]

2044 [Member]

2044 [Member]

Avista Corporation [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

Secured Debt [Member]

Secured Debt [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

Secured Debt [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

First Mortgage Bonds [Member]

2044 [Member]

First Mortgage Bonds [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maturity Year

'

'

'

'

'

'

'

'

'

'

'2018

'

'2018

'

'2019

'

'2020

'

'2022

'

'2023

'

'2028

'

'2032

[1]

'

'2034

[1]

'

'2035

'

'2037

'

'2040

'

'2041

'

'2047

'

'2016

'

'2044

'

'

'

Debt instrument, interest rate, stated percentage

'

'

'

8.45%

'

'

'

'

'

'

5.95%

'

'

'

5.45%

'

3.89%

'

5.13%

'

'

'

6.37%

'

'

'

'

'

6.25%

'

5.70%

'

5.55%

'

4.45%

'

4.23%

'

0.84%

'

4.54%

'

'

4.11%

Interest Rate, minimum

'

'

'

'

7.39%

7.18%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest Rate, maximum

'

'

'

'

7.45%

7.54%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Medium-Term Notes, Noncurrent

'

'

'

'

'

'

'

'

'

'

'

'

$22,500

$22,500

'

'

'

'

'

'

$13,500

$13,500

$25,000

$25,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Secured Debt

1,451,700

'

1,376,700

'

'

'

'

'

1,376,700

1,376,700

250,000

250,000

'

'

90,000

90,000

52,000

52,000

250,000

250,000

'

'

'

'

'

'

'

'

150,000

150,000

150,000

150,000

35,000

35,000

85,000

85,000

80,000

80,000

90,000

90,000

75,000

[2]

0

[2]

'

60,000

Other long-term debt and capital leases

1,412,211

'

1,272,425

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Settled interest rate swaps

-23,118

[3]

'

-23,560

[3]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unamortized debt discount

-954

'

-1,287

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total

1,502,382

'

1,356,483

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Pollution Control Bonds

-83,700

[1]

'

-83,700

[1]

'

'

'

66,700

17,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

66,700

[1]

66,700

[1]

17,000

[1]

17,000

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other Long-term Debt and Capital Lease Obligations

74,754

'

4,630

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Long-term Debt and Capital Lease Obligations, Current

-6,471

'

-358

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Payments for (Proceeds from) Derivative Instrument, Financing Activities

$0

$2,901

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$5,400

'

Document Period End Date

30-Sep-14

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

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

[2]

In September 2014, AEL&P issued $75.0 million of 4.54 percent first mortgage bonds due in 2044 to two institutional investors in the private placement market. The first mortgage bonds were issued under and in accordance with the AEL&P Mortgage and Deed of Trust, dated as of July 1, 2014.

[3]

Upon settlement of interest rate swaps, these are recorded as a regulatory asset or liability and included as part of long-term debt above. They are amortized as a component of interest expense over the life of the associated debt and included as a part of the Company's cost of debt calculation for ratemaking purposes.

LongTerm_Debt_Schedule_Of_Long1

Long-Term Debt (Schedule Of Long-Term Debt Maturities) (Details) (Alaska Electric Light & Power [Member], Capital Lease Obligations [Member], USD $)	Sep. 30, 2014
In Thousands, unless otherwise specified
Alaska Electric Light & Power [Member] | Capital Lease Obligations [Member]	'
Capital Leases Future Minimum Payments of Principal Remainder Of Fiscal Year	$526
Capital Leases Future Minimum Payments of Principal in Year Two	2,230
Capital Leases Future Minimum Payments of Principal in Year Three	2,350
Capital Leases Future Minimum Payments of Principal in Year Four	2,480
Capital Leases Future Minimum Payments of Principal in Year Five	2,615
Capital Leases Future Minimum Payments of Principal Thereafter	60,280
Capital Lease Obligations	70,481
Capital Leases Future Minimum Payments of Interest Remainder Of Fiscal Year	954
Capital Leases Future Minimum Payments of Interest Due in Two Years	3,690
Capital Leases Future Minimum Payments of Interest Due in Three Years	3,567
Capital Leases Future Minimum Payments of Interest Due in Four Years	3,438
Capital Leases Future Minimum Payments of Interest Due in Five Years	3,305
Capital Leases Future Minimum Payments of Interest Due Thereafter	28,529
Capital Leases Future Minimum Payments of Interest Due	43,483
Capital Leases Future Minimum Payments Remainder Of Fiscal Year	1,480
Capital Leases, Future Minimum Payments Due in Two Years	5,920
Capital Leases, Future Minimum Payments Due in Three Years	5,917
Capital Leases, Future Minimum Payments Due in Four Years	5,918
Capital Leases, Future Minimum Payments Due in Five Years	5,920
Capital Leases, Future Minimum Payments Due Thereafter	88,809
Capital Leases, Future Minimum Payments Due	$113,964

Fair_Value_Carrying_Value_And_

Fair Value (Carrying Value And Estimated Fair Value Of Financial Instruments) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Reported Value Measurement [Member] | Level 2 [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	$951,000	$951,000
Reported Value Measurement [Member] | Level 3 [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	417,000	342,000
Reported Value Measurement [Member] | Level 3 [Member] | Affiliated Entity [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	51,547	51,547
Reported Value Measurement [Member] | Level 3 [Member] | Nonrecourse Long-Term Debt [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	5,666	17,838
Estimate of Fair Value Measurement [Member] | Level 2 [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	1,100,345	1,054,512
Estimate of Fair Value Measurement [Member] | Level 3 [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	431,758	329,581
Estimate of Fair Value Measurement [Member] | Level 3 [Member] | Affiliated Entity [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	38,583	37,114
Estimate of Fair Value Measurement [Member] | Level 3 [Member] | Nonrecourse Long-Term Debt [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Long-term debt	5,756	18,636
Alaska Electric Light & Power [Member] | Capital Lease Obligations [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Capital Lease Obligations	70,481	'
Alaska Electric Light & Power [Member] | Reported Value Measurement [Member] | Level 3 [Member] | Capital Lease Obligations [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Capital Lease Obligations	70,481	0
Alaska Electric Light & Power [Member] | Estimate of Fair Value Measurement [Member] | Level 3 [Member] | Capital Lease Obligations [Member]	'	'
Fair Value and Carrying Value, by Balance Sheet Grouping [Line Items]	'	'
Capital Lease Obligations	$77,835	$0

Fair_Value_Fair_Value_Of_Asset

Fair Value (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013		Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	$66,849		$89,132		'	'
Securities available for sale:	'		69,361		'	'
Liability	103,191		89,675		'	'
Cash and cash equivalents	10,391		82,574		91,979	75,464
Fixed Income Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Cash and cash equivalents	1,000		700		'	'
Fair Value, Measurements, Recurring [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Foreign currency derivatives	'		1		'	'
Interest rate swaps	8,253		33,543		'	'
Money Market Funds, Fair Value	'		11,180		'	'
Funds held in trust account of Spokane Energy	1,600		1,600		'	'
Total	22,807		127,991		'	'
Foreign currency derivative liabilities at fair value	280		0		'	'
Interest rate swaps	16,708		'		'	'
Total	35,957		29,231		'	'
Fair Value, Measurements, Recurring [Member] | Energy commodity derivatives [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	5,027		3,876		'	'
Liability	4,282		12,796		'	'
Fair Value, Measurements, Recurring [Member] | Power Option Agreement [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Liability	362		775		'	'
Fair Value, Measurements, Recurring [Member] | Natural Gas Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	0		'		'	'
Liability	1,471		1,219		'	'
Fair Value, Measurements, Recurring [Member] | Power Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	0		0		'	'
Liability	12,854		14,441		'	'
Fair Value, Measurements, Recurring [Member] | U.S. Government Agency [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		61,078		'	'
Fair Value, Measurements, Recurring [Member] | Municipal [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		3,518		'	'
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - financial [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		3,000		'	'
Fair Value, Measurements, Recurring [Member] | Corporate fixed income - industrial [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		765		'	'
Fair Value, Measurements, Recurring [Member] | Certificates of deposits [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		1,000		'	'
Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Deferred compensation assets:	1,831	[1]	1,960	[1]	'	'
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Deferred compensation assets:	6,096	[1]	6,470	[1]	'	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Money Market Funds, Fair Value	'		11,180		'	'
Funds held in trust account of Spokane Energy	1,600		1,600		'	'
Total	9,527		21,210		'	'
Total	0		0		'	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Fixed Income Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Deferred compensation assets:	1,831	[1]	1,960	[1]	'	'
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Deferred compensation assets:	6,096	[1]	6,470	[1]	'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Foreign currency derivatives	'		7		'	'
Interest rate swaps	13,300		33,543		'	'
Total	65,991		158,154		'	'
Foreign currency derivative liabilities at fair value	280		6		'	'
Interest rate swaps	34,485		'		'	'
Total	87,646		72,901		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Energy commodity derivatives [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	52,691		55,243		'	'
Liability	52,881		72,895		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government Agency [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		61,078		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Municipal [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		3,518		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate fixed income - financial [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		3,000		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate fixed income - industrial [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		765		'	'
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Certificates of deposits [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Securities available for sale:	'		1,000		'	'
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Total	858		339		'	'
Total	15,545		16,774		'	'
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Option Agreement [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Liability	362		775		'	'
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	58		'		'	'
Liability	1,529		1,219		'	'
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Power Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	800		339		'	'
Liability	13,654		14,780		'	'
Fair Value, Measurements, Recurring [Member] | Netting [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Foreign currency derivatives	'		-6	[2]	'	'
Interest rate swaps	-5,047		'		'	'
Total	-53,569	[2]	-51,712	[2]	'	'
Foreign currency derivative liabilities at fair value	0		-6		'	'
Interest rate swaps	-17,777		'		'	'
Total	-67,234	[2]	-60,444	[2]	'	'
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Energy commodity derivatives [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	-47,664	[2]	-51,367	[2]	'	'
Liability	-48,599	[2]	-60,099	[2]	'	'
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Natural Gas Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	-58		'		'	'
Liability	-58		0	[2]	'	'
Fair Value, Measurements, Recurring [Member] | Netting [Member] | Power Exchange Agreements [Member]	'		'		'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'		'		'	'
Gross Asset	-800		-339	[2]	'	'
Liability	($800)		($339)	[2]	'	'
[1]	These assets are trading securities and are included in other property and investments-net on the Condensed Consolidated Balance Sheets.
[2]	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.

Fair_Value_Quantitative_Inform

Fair Value (Quantitative Information) (Details) (USD $)

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2014

In Thousands, unless otherwise specified

Power Exchange Agreements [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Average [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

WASHINGTON

IDAHO

Sales [Member]

Sales [Member]

Purchase [Member]

Purchase [Member]

2014 to 2019 [Member]

Black Scholes Merton [Member]

2014 [Member]

2015 [Member]

2019 [Member]

2017 [Member]

Power Exchange Agreements [Member]

Power Option Agreement [Member]

Power Exchange Agreements [Member]

Power Option Agreement [Member]

Power Exchange Agreements [Member]

Power Exchange Agreements [Member]

Power Exchange Agreements [Member]

Power Option Agreement [Member]

Power Option Agreement [Member]

Natural Gas Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

Average [Member]

Average [Member]

Minimum [Member]

Maximum [Member]

Minimum [Member]

Maximum [Member]

Surrogate Facility Pricing [Member]

Black Scholes Merton [Member]

Black Scholes Merton [Member]

Black Scholes Merton [Member]

Black Scholes Merton [Member]

Surrogate Facility Pricing [Member]

Black Scholes Merton [Member]

Surrogate Facility Pricing [Member]

Black Scholes Merton [Member]

Surrogate Facility Pricing [Member]

Power Exchange Agreements [Member]

Power Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

Natural Gas Exchange Agreements [Member]

MWh

MWh

MWh

MWh

Surrogate Facility Pricing [Member]

Surrogate Facility Pricing [Member]

Internally Derived Weighted Average Cost Of Gas [Member]

Internally Derived Weighted Average Cost Of Gas [Member]

Internally Derived Weighted Average Cost Of Gas [Member]

Internally Derived Weighted Average Cost Of Gas [Member]

MMBTU

MMBTU

MMBTU

MMBTU

Fair Value Inputs, Assets, Quantitative Information [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gross Liability

($103,191)

($89,675)

'

'

'

'

'

'

'

'

'

'

'

($12,854)

($14,441)

($362)

($775)

($1,471)

($1,219)

'

'

'

'

'

'

Operation and Maintenance Charges

'

'

'

'

'

'

'

'

30.66

[1]

'

55.56

[1]

'

42.9

[1]

'

'

'

'

'

'

43.11

42.9

'

'

'

'

Escalation Factor

'

'

3.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Price Risk Option Strike Price

'

'

'

'

'

56.2

67.81

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value Assumptions, Expected Volatility Rate

'

'

'

20.00%

[2]

30.00%

[2]

'

'

19.00%

[2]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Forward Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4.19

4.72

3.43

3.68

Transaction/Delivery Volumes

'

'

'

'

'

'

'

'

310,103

32,472

397,116

287,147

'

'

'

'

'

'

'

'

'

279,990

310,000

280,000

310,000

[1]

The average O&M charges for the delivery year beginning in November 2014 were $42.90 per MWh. For ratemaking purposes the average O&M charges to be included for recovery in retail rates vary slightly between regulatory jurisdictions. The average O&M charges for the delivery year beginning in 2014 were $43.11 for Washington and $42.90 for Idaho.

[2]

The estimated volatility rate of 0.20 is compared to actual quoted volatility rates of 0.30 for 2014 to 0.19 in October 2017.

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) (Fair Value, Inputs, Level 3 [Member], USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'		'		'
Beginning Balance	($10,707)		($23,797)		($16,435)		($22,551)
Included in net income	0		0		0		0
Included in other comprehensive income	0		0		0		0
Included in regulatory assets/liabilities	-3,980	[1]	5,800	[1]	5,329	[1]	2,243	[1]
Purchases	0		0		0		0
Issuances	0		0		0		0
Settlements	0		-1		-3,581		2,310
Transfers from other categories	0		0		0		0
Ending Balance	-14,687		-17,998		-14,687		-17,998
Natural Gas Exchange Agreements [Member]	'		'		'		'
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'		'		'
Beginning Balance	-2,183		-1,022		-1,219		-2,379
Included in net income	0		0		0		0
Included in other comprehensive income	0		0		0		0
Included in regulatory assets/liabilities	712	[1]	-170	[1]	2,796	[1]	1,637	[1]
Purchases	0		0		0		0
Issuances	0		0		0		0
Settlements	0		-1		-3,048		-451
Transfers from other categories	0		0		0		0
Ending Balance	-1,471		-1,193		-1,471		-1,193
Power Exchange Agreements [Member]	'		'		'		'
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'		'		'
Beginning Balance	-7,919		-22,179		-14,441		-18,692
Included in net income	0		0		0		0
Included in other comprehensive income	0		0		0		0
Included in regulatory assets/liabilities	-4,935	[1]	6,135	[1]	2,120	[1]	-113	[1]
Purchases	0		0		0		0
Issuances	0		0		0		0
Settlements	0		0		-533		2,761
Transfers from other categories	0		0		0		0
Ending Balance	-12,854		-16,044		-12,854		-16,044
Power Option Agreement [Member]	'		'		'		'
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'		'		'		'
Beginning Balance	-605		-596		-775		-1,480
Included in net income	0		0		0		0
Included in other comprehensive income	0		0		0		0
Included in regulatory assets/liabilities	243	[1]	-165	[1]	413	[1]	719	[1]
Purchases	0		0		0		0
Issuances	0		0		0		0
Settlements	0		0		0		0
Transfers from other categories	0		0		0		0
Ending Balance	($362)		($761)		($362)		($761)
[1]	(1)The UTC and the IPUC issued accounting orders authorizing Avista Corp. to offset commodity derivative assets or liabilities with a regulatory asset or liability. This accounting treatment defers the recognition of mark-to-market gains and losses on energy commodity transactions until the period of delivery. The orders provide for Avista Corp. to not recognize the unrealized gain or loss on utility derivative commodity instruments in the Condensed Consolidated Statements of Income. Realized gains or losses are recognized in the period of delivery, subject to approval for recovery through retail rates. Realized gains and losses, subject to regulatory approval, result in adjustments to retail rates through purchased gas cost adjustments, the ERM in Washington, the PCA mechanism in Idaho, and periodic general rates cases.

Earnings_Per_Share_Attributabl

Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Income (Loss) from Continuing Operations Attributable to Parent	$10,506	$8,450	$89,236	$73,882
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	-55	2,963	70,585	5,529
Numerator:	'	'	'	'
Net income attributable to Avista Corporation shareholders	10,451	11,413	159,821	79,411
Subsidiary earnings adjustment for dilutive securities	0	-81	5	-163
Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	($55)	$2,882	$70,590	$5,366
Denominator:	'	'	'	'
Weighted-average number of common shares outstanding-basic	63,934	59,994	61,413	59,933
Performance and restricted stock awards	310	38	212	31
Weighted-average number of common shares outstanding-diluted	64,244	60,032	61,625	59,964
Earnings per common share attributable to Avista Corporation:	'	'	'	'
Basic	$0.16	$0.19	$2.60	$1.32
Diluted (usd per share)	$0.16	$0.19	$2.59	$1.32
Income (Loss) from Continuing Operations, Per Basic Share	$0.16	$0.14	$1.45	$1.23
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	$0	$0.05	$1.15	$0.09
Income (Loss) from Continuing Operations, Per Diluted Share	$0.16	$0.14	$1.45	$1.23
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$0	$0.05	$1.14	$0.09

Commitments_And_Contingencies_

Commitments And Contingencies (Details) (USD $)	1 Months Ended	9 Months Ended
	31-May-04	Sep. 30, 2014
		hydroelectric_plant
		employee
		gal
Number Of Bargaining Unit Employees Oregon	'	50
Amount of Regulatory Costs Not yet Approved	'	$1,300,000
Gallons of Diesel Spilled	'	10,000
Investigation review bid maximum (per MW)	250	'
Litigation Settlement, Amount	'	$15,000,000
Number of hydroelectric plants	'	6
Number of years, license issued	'	'50 years
Avista Utilities [Member]	'	'
Percentage Of Employees, Collective Bargaining Agreement	'	45.00%
Majority Of Bargaining Unit Employees, Percentage	'	90.00%
Alaska Electric Light & Power [Member]	'	'
Percentage Of Employees, Collective Bargaining Agreement	'	54.00%

Information_By_Business_Segmen2

Information By Business Segments (Details) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating revenues	$301,558		$289,477		$1,060,716		$1,037,464		'
Resource costs	131,588		131,136		481,007		487,277		'
Other operating expenses	82,760		79,808		227,709		229,796		'
Depreciation and amortization	33,448		29,994		95,652		87,319		'
Income from operations	32,762		29,827		185,835		166,935		'
Interest expense	18,755	[1]	19,285	[1]	56,269	[1]	58,206	[1]	'
Income taxes	7,301		3,367		51,274		41,929		'
Net income (loss) attributable to Avista Corporation	10,451		11,413		159,821		79,411		'
Income (Loss) from Continuing Operations Attributable to Parent	10,506		8,450		89,236		73,882		'
Payments to Acquire Other Property, Plant, and Equipment	93,444		75,392		230,060		220,851		'
Total assets	4,336,346		'		4,336,346		'		4,361,923
Avista Utilities [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating revenues	282,555		278,923		1,023,684		1,008,669		'
Resource costs	128,591		131,136		478,010		487,277		'
Other operating expenses	69,403		69,596		204,089		200,824		'
Depreciation and amortization	32,006		29,823		93,912		86,783		'
Income from operations	32,048		29,657		177,653		167,648		'
Interest expense	18,247	[1]	18,837	[1]	55,215	[1]	56,635	[1]	'
Income taxes	7,146		3,945		48,068		43,278		'
Net income (loss) attributable to Avista Corporation	10,349		9,447		85,030		76,265		'
Payments to Acquire Other Property, Plant, and Equipment	92,197		75,368		228,711		220,712		'
Total assets	3,991,330		'		3,991,330		'		3,940,998
Alaska Electric Light & Power [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating revenues	9,157		0		9,157		0		'
Resource costs	2,997		0		2,997		0		'
Other operating expenses	3,106		0		3,106		0		'
Depreciation and amortization	1,288		0		1,288		0		'
Income from operations	1,273		0		1,273		0		'
Interest expense	485	[1]	0	[1]	485	[1]	0	[1]	'
Income taxes	329		0		329		0		'
Net income (loss) attributable to Avista Corporation	511		0		511		0		'
Payments to Acquire Other Property, Plant, and Equipment	1,053		0		1,053		0		'
Total assets	261,402		'		261,402		'		0
Total Utility [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating revenues	291,712		278,923		1,032,841		1,008,669		'
Resource costs	131,588		131,136		481,007		487,277		'
Other operating expenses	72,509		69,596		207,195		200,824		'
Depreciation and amortization	33,294		29,823		95,200		86,783		'
Income from operations	33,321		29,657		178,926		167,648		'
Interest expense	18,732	[1]	18,837	[1]	55,700	[1]	56,635	[1]	'
Income taxes	7,475		3,945		48,397		43,278		'
Net income (loss) attributable to Avista Corporation	10,860		9,447		85,541		76,265		'
Payments to Acquire Other Property, Plant, and Equipment	93,250	[2]	75,368	[2]	229,764	[2]	220,712	[2]	'
Total assets	4,252,732		'		4,252,732		'		3,940,998
Other Business Segment [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating revenues	10,296		11,004		29,225		30,145		'
Resource costs	0		0		0		0		'
Other operating expenses	10,701		10,662		21,864		30,322		'
Depreciation and amortization	154		171		452		536		'
Income from operations	-559		170		6,909		-713		'
Interest expense	186	[1]	525	[1]	899	[1]	1,801	[1]	'
Income taxes	-174		-578		2,877		-1,349		'
Net income (loss) attributable to Avista Corporation	-354		-1,074		3,528		-2,613		'
Payments to Acquire Other Property, Plant, and Equipment	194		24		296		139		'
Total assets	83,614		'		83,614		'		81,282
Ecova [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Total assets	'		'		'		'		339,600
Intersegment Eliminations [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Operating revenues	-450	[3]	-450	[3]	-1,350	[3]	-1,350	[3]	'
Resource costs	0	[3]	0	[3]	0	[3]	0	[3]	'
Other operating expenses	-450	[3]	-450	[3]	-1,350	[3]	-1,350	[3]	'
Depreciation and amortization	0	[3]	0	[3]	0	[3]	0	[3]	'
Income from operations	0	[3]	0	[3]	0	[3]	0	[3]	'
Interest expense	-163	[1],[3]	-77	[1],[3]	-330	[1],[3]	-230	[1],[3]	'
Income taxes	0	[3]	0	[3]	0	[3]	0	[3]	'
Net income (loss) attributable to Avista Corporation	0	[3]	77	[3]	167	[3]	230	[3]	'
Payments to Acquire Other Property, Plant, and Equipment	0	[3]	0	[3]	0	[3]	0	[3]	'
Total assets	0	[3]	'		0	[3]	'		0	[3]
Avista Utilities and Other Businesses [Member]	'		'		'		'		'
Segment Reporting Information [Line Items]	'		'		'		'		'
Total assets	'		'		'		'		$4,022,280	[4]
[1]	Including interest expense to affiliated trusts.
[2]	The capital expenditures for the other businesses are included as other capital expenditures on the Condensed Consolidated Statements of Cash Flows. The remainder of the balance included in other capital expenditures on the Condensed Consolidated Statements of Cash Flows are related to Ecova.
[3]	Intersegment eliminations reported as operating revenues and resource costs represent intercompany purchases and sales of electric capacity and energy. Intersegment eliminations reported as interest expense and net income (loss) attributable to Avista Corp. shareholders represent intercompany interest.
[4]	The consolidated total assets presented here as of December 31, 2013 exclude total assets at Ecova of $339.6 million.