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]	Total Avista Corporation Stockholders' Equity [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
Issuance of common stock		335,154
Equity compensation expense		2,241
Issuance of common stock, net of issuance costs		3,575
Equity transactions of consolidated subsidiaries		49
Other comprehensive loss	479		479
Net income attributable to Avista Corporation shareholders	56,566			56,566
Cash dividends paid (common stock)				(34,101)
Total equity	1,216,414				1,216,842
Net income (loss) attributable to noncontrolling interests						71	108
Issuance of subsidiary noncontrolling interests	3,714						3,714
Deconsolidation of variable interest entity						(673)
Other						0
Purchase of subsidiary noncontrolling interests							(784)
Valuation adjustments and other noncontrolling interests activity				2,332			(1,423)
Ending Balance at Jun. 30, 2012		861,053	(5,158)	360,947		(428)	53,424
Ending Balance (in shares) at Jun. 30, 2012		58,757,935
Beginning Balance at Dec. 31, 2012	1,259,477	889,237	(6,700)	376,940		17,658	4,938
Beginning Balance (in shares) at Dec. 31, 2012	59,812,796	59,812,796
Issuance of common stock		167,227
Equity compensation expense		2,968
Issuance of common stock, net of issuance costs		3,017
Equity transactions of consolidated subsidiaries		33
Other comprehensive loss	(936)		(936)
Net income attributable to Avista Corporation shareholders	67,998			67,998
Cash dividends paid (common stock)				(36,667)
Total equity	1,314,421				1,293,814
Net income (loss) attributable to noncontrolling interests						777	56
Issuance of subsidiary noncontrolling interests	0						0
Deconsolidation of variable interest entity						0
Other						2,172
Purchase of subsidiary noncontrolling interests							(325)
Valuation adjustments and other noncontrolling interests activity				(2,076)			3,148
Ending Balance at Jun. 30, 2013	$ 1,293,814	$ 895,255	$ (7,636)	$ 406,195		$ 20,607	$ 7,817
Ending Balance (in shares) at Jun. 30, 2013	59,980,023	59,980,023