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, 2013		$ 896,993	$ (5,819)	$ 407,092	$ 20,001	$ 15,889
Beginning Balance (in shares) at Dec. 31, 2013		60,076,752
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable						24
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable					458
Issuance of common stock		84,388
Equity compensation expense		1,619
Issuance of common stock, net of issuance costs		638
Adjustments Related to Tax Withholding for Share-based Compensation		0
Stock Repurchased During Period, Value		0		0
Equity transactions of consolidated subsidiaries		(213)
Other comprehensive loss	894		894
Net income attributable to Avista Corporation shareholders	48,499			48,499
Cash dividends paid (common stock)				(19,217)
Total equity	1,351,113
Other					172
Purchase of subsidiary noncontrolling interests						(3)
Valuation adjustments and other noncontrolling interests activity				4		(50)
Stock Repurchased During Period, Shares		0
Ending Balance at Mar. 31, 2014	1,330,482	899,037	(4,925)	436,370	20,631	15,960
Ending Balance (in shares) at Mar. 31, 2014		60,161,140
Beginning Balance at Dec. 31, 2014	1,483,671	999,960	(7,888)	491,599	(429)	0
Beginning Balance (in shares) at Dec. 31, 2014	60,076,752	62,243,374
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable						0
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable					13
Issuance of common stock		117,159
Equity compensation expense		1,513
Issuance of common stock, net of issuance costs		413
Adjustments Related to Tax Withholding for Share-based Compensation		(1,480)
Stock Repurchased During Period, Value		(1,431)		(1,489)
Equity transactions of consolidated subsidiaries		0
Other comprehensive loss	246		246
Net income attributable to Avista Corporation shareholders	46,449			46,449
Cash dividends paid (common stock)				(20,717)
Total equity	1,506,759
Other					0
Purchase of subsidiary noncontrolling interests						0
Valuation adjustments and other noncontrolling interests activity				0		0
Stock Repurchased During Period, Shares	(89,400)	(89,400)
Ending Balance at Mar. 31, 2015	$ 1,507,175	$ 998,975	$ (7,642)	$ 515,842	$ (416)	$ 0
Ending Balance (in shares) at Mar. 31, 2015	62,271,133	62,271,133