Condensed Consolidated Statements Of Equity And Redeemable Noncontrolling Interests (USD $) In Thousands, except Share data	Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Total Avista Corporation Stockholders' Equity [Member]	Noncontrolling Interests [Member]	Redeemable Noncontrolling Interests [Member]	Total
Beginning Balance at Dec. 31, 2010	$ 827,592	$ (4,326)	$ 302,518		$ (600)	$ 46,722
Beginning Balance (in shares) at Dec. 31, 2010	57,119,723
Issuance of common stock	502,495
Equity compensation expense	889
Issuance of common stock, net of issuance costs	8,458
Equity transactions of consolidated subsidiaries	(3,322)
Other comprehensive income (loss)		(196)					(196)
Net income attributable to Avista Corporation			41,918				41,918
Cash dividends paid (common stock)			(15,780)
Total equity				1,160,379			1,159,807
Net income (loss) attributable to noncontrolling interests					33	452
Other					(5)
Purchase of subsidiary noncontrolling interests						(5,639)
Valuation adjustments and other noncontrolling interests activity			2,628			1,282
Ending Balance at Mar. 31, 2011	833,617	(4,522)	331,284		(572)	42,817
Ending Balance (in shares) at Mar. 31, 2011	57,622,218
Beginning Balance at Dec. 31, 2011	855,188	(5,637)	336,150		174	51,809	1,185,701
Beginning Balance (in shares) at Dec. 31, 2011	58,422,781						58,422,781
Issuance of common stock	248,020
Equity compensation expense	1,120
Issuance of common stock, net of issuance costs	1,437
Equity transactions of consolidated subsidiaries	2
Other comprehensive income (loss)		211					211
Net income attributable to Avista Corporation			38,388				38,388
Cash dividends paid (common stock)			(17,073)
Total equity				1,208,139			1,207,671
Net income (loss) attributable to noncontrolling interests					31	(206)
Deconsolidation of variable interest entity					(673)
Issuance of subsidiary noncontrolling interests						3,714	3,714
Purchase of subsidiary noncontrolling interests						(134)
Valuation adjustments and other noncontrolling interests activity			(1,647)			2,450
Ending Balance at Mar. 31, 2012	$ 857,747	$ (5,426)	$ 355,818		$ (468)	$ 57,633	$ 1,208,139
Ending Balance (in shares) at Mar. 31, 2012	58,670,801						58,670,801