Consolidated Statements Of Equity And Redeemable Noncontrolling Interests (USD $) In Thousands, except Share data	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]	Total
Beginning Balance at Dec. 31, 2008	$ 774,986	$ (6,092)	$ 227,989			$ 39,846
Beginning Balance (in shares) at Dec. 31, 2008	54,487,574
Issuance of common stock through equity compensation plans (in shares)	343,498
Issuance of common stock through Employee Investment Plan (401-K), (in shares)	4,309
Issuance of common stock through Dividend Reinvestment Plan, (in shares)	1,400
Equity compensation expense	2,711
Issuance of common stock through equity compensation plans	2,666
Issuance of common stock through Employee Investment Plan (401-K)	71
Issuance of common stock through Dividend Reinvestment Plan	26
Issuance of common stock, net of issuance costs	(141)
Equity transactions of consolidated subsidiaries	(1,672)
Other comprehensive income (loss)		3,742					3,742
Net income attributable to Avista Corporation			87,071				87,071
Cash dividends paid (common stock)			(44,360)
Total equity				1,051,287			1,050,614
Net income (loss) attributable to noncontrolling interests					(295)	1,872
Other					(378)
Purchase of subsidiary noncontrolling interests						(5,450)
Valuation adjustments and other noncontrolling interests activity			4,290			(1,435)
Ending Balance at Dec. 31, 2009	778,647	(2,350)	274,990		(673)	34,833
Ending Balance (in shares) at Dec. 31, 2009	54,836,781
Issuance of common stock through equity compensation plans (in shares)	141,645
Issuance of common stock through Employee Investment Plan (401-K), (in shares)	11,116
Issuance of common stock through Dividend Reinvestment Plan, (in shares)	76,071
Issuance of common stock	2,054,110
Equity compensation expense	3,097
Issuance of common stock through equity compensation plans	1,942
Issuance of common stock through Employee Investment Plan (401-K)	235
Issuance of common stock through Dividend Reinvestment Plan	1,451
Issuance of common stock, net of issuance costs	42,607
Equity transactions of consolidated subsidiaries	(387)
Other comprehensive income (loss)		(1,976)					(1,976)
Net income attributable to Avista Corporation			92,425				92,425
Cash dividends paid (common stock)			(55,682)
Total equity				1,125,784			1,125,184
Net income (loss) attributable to noncontrolling interests					66	2,457
Other					7
Purchase of subsidiary noncontrolling interests						(2,593)
Valuation adjustments and other noncontrolling interests activity			(9,215)			12,025
Ending Balance at Dec. 31, 2010	827,592	(4,326)	302,518		(600)	46,722	1,125,784
Ending Balance (in shares) at Dec. 31, 2010	57,119,723						57,119,723
Issuance of common stock through equity compensation plans (in shares)	275,057
Issuance of common stock through Employee Investment Plan (401-K), (in shares)	43,179
Issuance of common stock through Dividend Reinvestment Plan, (in shares)	177,822
Issuance of common stock	807,000
Equity compensation expense	3,635
Issuance of common stock through equity compensation plans	1,879
Issuance of common stock through Employee Investment Plan (401-K)	1,073
Issuance of common stock through Dividend Reinvestment Plan	4,299
Issuance of common stock, net of issuance costs	19,213
Equity transactions of consolidated subsidiaries	(2,503)
Other comprehensive income (loss)		(1,311)					(1,311)
Net income attributable to Avista Corporation			100,224				100,224
Cash dividends paid (common stock)			(63,737)
Total equity				1,185,701			1,185,875
Net income (loss) attributable to noncontrolling interests					756	2,559
Other					18
Purchase of subsidiary noncontrolling interests						(6,179)
Valuation adjustments and other noncontrolling interests activity			(2,855)			8,707
Ending Balance at Dec. 31, 2011	$ 855,188	$ (5,637)	$ 336,150		$ 174	$ 51,809	$ 1,185,701
Ending Balance (in shares) at Dec. 31, 2011	58,422,781						58,422,781