Consolidated Statements Of Equity And Redeemable Noncontrolling Interests (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]	Redeemable Noncontrolling Interests [Member]
Beginning Balance at Dec. 31, 2011		$ 855,188	$ (5,637)	$ 336,150	$ 174	$ 51,809
Beginning Balance (in shares) at Dec. 31, 2011		58,422,781
Net income attributable to noncontrollling interests					451
Net income attributable to noncontrolling interests						139
Issuance of common stock through equity compensation plans (in shares)		245,661
Issuance of common stock through Employee Investment Plan (401-K), (in shares)		45,715
Issuance of common stock through Dividend Reinvestment Plan, (in shares)		167,448
Shares issued through sales agency agreements		931,191
Stock Issued During Period, Shares, Acquisitions	0
Equity compensation expense		5,716
Issuance of common stock through equity compensation plans		1,535
Issuance of common stock through Employee Investment Plan (401-K)		1,165
Issuance of common stock through Dividend Reinvestment Plan		4,226
Issuance of common stock through sales agency agreements, net of issuance costs		23,383
Stock Issued During Period, Value, Acquisitions Net of Issuance Costs	0
Stock Repurchased During Period, Value		0		0
Equity transactions of consolidated subsidiaries		(1,015)
Other comprehensive income (loss)	(1,063)		(1,063)
Net income attributable to Avista Corporation shareholders	78,210			78,210
Cash dividends paid (common stock)				(68,552)
Total equity	1,277,135
Issuance of subsidiary noncontrolling interests					0	3,714
Deconsolidation of variable interest entity					673
Other					33
Purchase of subsidiary noncontrolling interests					(117)	(784)
Expiration of subsidiary noncontrolling interests redemption rights				23,805	17,790	41,595
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0
Valuation adjustments and other noncontrolling interests activity				7,327		(8,345)
Stock Repurchased During Period, Shares		0
Payments for Repurchase of Redeemable Noncontrolling Interest	0	0
Adjustments to Additional Paid in Capital, Income Tax Deficiency from Share-based Compensation		(961)
Ending Balance at Dec. 31, 2012	1,259,477	889,237	(6,700)	376,940	17,658	4,938
Ending Balance (in shares) at Dec. 31, 2012		59,812,796
Net income attributable to noncontrollling interests					1,066
Net income attributable to noncontrolling interests						151
Issuance of common stock through equity compensation plans (in shares)		58,002
Issuance of common stock through Employee Investment Plan (401-K), (in shares)		42,073
Issuance of common stock through Dividend Reinvestment Plan, (in shares)		163,881
Shares issued through sales agency agreements		0
Stock Issued During Period, Shares, Acquisitions	0
Equity compensation expense		6,002
Issuance of common stock through equity compensation plans		(1,342)
Issuance of common stock through Employee Investment Plan (401-K)		1,127
Issuance of common stock through Dividend Reinvestment Plan		4,360
Issuance of common stock through sales agency agreements, net of issuance costs		0
Stock Issued During Period, Value, Acquisitions Net of Issuance Costs	0
Stock Repurchased During Period, Value		0		0
Equity transactions of consolidated subsidiaries		(3,007)
Other comprehensive income (loss)	881		881
Net income attributable to Avista Corporation shareholders	111,077			111,077
Cash dividends paid (common stock)				(73,276)
Total equity	1,318,267
Issuance of subsidiary noncontrolling interests					480	0
Deconsolidation of variable interest entity					0
Other					4,979
Purchase of subsidiary noncontrolling interests					(4,182)	(405)
Expiration of subsidiary noncontrolling interests redemption rights				0	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0
Valuation adjustments and other noncontrolling interests activity				(7,649)		11,205
Stock Repurchased During Period, Shares		0
Payments for Repurchase of Redeemable Noncontrolling Interest	0	0
Excess Tax Benefit from Share-based Compensation, Financing Activities		616
Ending Balance at Dec. 31, 2013	1,298,266	896,993	(5,819)	407,092	20,001	15,889
Ending Balance (in shares) at Dec. 31, 2013	60,076,752	60,076,752
Net income attributable to noncontrollling interests					240
Net income attributable to noncontrolling interests						(4)
Issuance of common stock through equity compensation plans (in shares)		51,127
Issuance of common stock through Employee Investment Plan (401-K), (in shares)		33,168
Issuance of common stock through Dividend Reinvestment Plan, (in shares)		110,501
Shares issued through sales agency agreements		0
Stock Issued During Period, Shares, Acquisitions	4,501,441
Equity compensation expense		7,676
Issuance of common stock through equity compensation plans		108
Issuance of common stock through Employee Investment Plan (401-K)		1,005
Issuance of common stock through Dividend Reinvestment Plan		3,441
Issuance of common stock through sales agency agreements, net of issuance costs		0
Stock Issued During Period, Value, Acquisitions Net of Issuance Costs	149,625
Stock Repurchased During Period, Value		(40,486)		(39,370)
Equity transactions of consolidated subsidiaries		(1,062)
Other comprehensive income (loss)	(2,069)		(2,069)
Net income attributable to Avista Corporation shareholders	192,041			192,041
Cash dividends paid (common stock)				(78,314)
Total equity	1,483,242
Issuance of subsidiary noncontrolling interests					0	0
Deconsolidation of variable interest entity					0
Other					2,942
Purchase of subsidiary noncontrolling interests					0	(12)
Expiration of subsidiary noncontrolling interests redemption rights				0	0	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(23,612)
Valuation adjustments and other noncontrolling interests activity				10,150		(15,873)
Stock Repurchased During Period, Shares		(2,529,615)
Payments for Repurchase of Redeemable Noncontrolling Interest	(20,871)	(20,871)
Excess Tax Benefit from Share-based Compensation, Financing Activities		3,531
Ending Balance at Dec. 31, 2014	$ 1,483,671	$ 999,960	$ (7,888)	$ 491,599	$ (429)	$ 0
Ending Balance (in shares) at Dec. 31, 2014	62,243,374	62,243,374