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
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable						121
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable					234
Issuance of common stock		1,332,089
Equity compensation expense		3,354
Issuance of common stock, net of issuance costs		28,699
Equity transactions of consolidated subsidiaries		289
Other comprehensive loss	740		740
Net income attributable to Avista Corporation shareholders	62,352			62,352
Cash dividends paid (common stock)				(51,215)
Total equity	1,277,182
Issuance of subsidiary noncontrolling interests	3,714					3,714
Deconsolidation of variable interest entity					(673)
Expiration Of Subsidiary Noncontrolling Interests Redemption Rights				23,805	17,790	(41,595)
Other					30
Purchase of subsidiary noncontrolling interests					(117)	(784)
Valuation adjustments and other noncontrolling interests activity				6,019		(6,539)
Ending Balance at Sep. 30, 2012	1,259,744	887,530	(4,897)	377,111	17,438	6,726
Ending Balance (in shares) at Sep. 30, 2012		59,754,870
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
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
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
Issuance of subsidiary noncontrolling interests	0					0
Deconsolidation of variable interest entity					0
Expiration Of Subsidiary Noncontrolling Interests Redemption Rights				0	0	0
Other					2,163
Purchase of subsidiary noncontrolling interests					0	(379)
Valuation adjustments and other noncontrolling interests activity				(2,335)		3,652
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	60,029,209