Consolidated Statements Of Equity And Redeemable Noncontrolling Interests - USD ($) $ in Thousands	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]
Excess Tax Benefit from Share-based Compensation, Financing Activities		$ 42
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable					$ 13
Beginning Balance (in shares) at Dec. 31, 2014		62,243,374
Issuance of common stock		117,159
Beginning Balance at Dec. 31, 2014		$ 999,960	$ (7,888)	$ 491,599	(429)
Equity compensation expense		1,513
Issuance of common stock, net of issuance costs		371
Adjustments Related to Tax Withholding for Share-based Compensation		(1,480)
Stock Repurchased During Period, Value		(1,431)		(1,489)
Other comprehensive loss	$ 246		246
Net income attributable to Avista Corporation shareholders	46,449			46,449
Cash dividends paid (common stock)				(20,717)
Ending Balance at Mar. 31, 2015	1,507,175	$ 998,975	(7,642)	515,842	(416)
Ending Balance (in shares) at Mar. 31, 2015		62,271,133
Stock Repurchased During Period, Shares		(89,400)
Total equity	1,506,759
Total equity	$ 1,528,287
Excess Tax Benefit from Share-based Compensation, Financing Activities		$ 1,597
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable					16
Beginning Balance (in shares) at Dec. 31, 2015	62,312,651	62,312,651
Issuance of common stock		895,408
Beginning Balance at Dec. 31, 2015	$ 1,528,626	$ 1,004,336	(6,650)	530,940	(339)
Equity compensation expense		1,967
Issuance of common stock, net of issuance costs		27,150
Adjustments Related to Tax Withholding for Share-based Compensation		(3,027)
Stock Repurchased During Period, Value		0		0
Other comprehensive loss	(1,229)		(1,229)
Net income attributable to Avista Corporation shareholders	56,052			56,052
Cash dividends paid (common stock)				(21,545)
Ending Balance at Mar. 31, 2016	$ 1,589,591	$ 1,032,023	$ (7,879)	$ 565,447	$ (323)
Ending Balance (in shares) at Mar. 31, 2016	63,208,059	63,208,059
Stock Repurchased During Period, Shares		0
Total equity	$ 1,589,268