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, 2012		$ 889,237	$ (6,700)	$ 376,940	$ 17,658	$ 4,938
Beginning Balance (in shares) at Dec. 31, 2012		59,812,796
Noncontrolling Interest, Decrease from Deconsolidation	0
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
Stock Repurchased During Period, Value		0		0
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
Other					2,163
Purchase of subsidiary noncontrolling interests						(379)
Valuation adjustments and other noncontrolling interests activity				(2,335)		3,652
Payments for Repurchase of Redeemable Noncontrolling Interest	0
Excess Tax Benefit from Share-based Compensation, Financing Activities	0
Stock Repurchased During Period, Shares		0
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
Beginning Balance at Dec. 31, 2013	1,298,266	896,993	(5,819)	407,092	20,001	15,889
Beginning Balance (in shares) at Dec. 31, 2013	60,076,752	60,076,752
Noncontrolling Interest, Decrease from Deconsolidation	(23,612)
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable						(4)
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable					217
Issuance of common stock		4,685,953
Equity compensation expense		6,061
Issuance of common stock, net of issuance costs		153,501
Stock Repurchased During Period, Value		(30,794)		(30,169)
Equity transactions of consolidated subsidiaries		(1,062)
Other comprehensive loss	1,921		1,921
Net income attributable to Avista Corporation shareholders	159,821			159,821
Cash dividends paid (common stock)				(58,552)
Total equity	1,491,757
Other					2,943
Purchase of subsidiary noncontrolling interests						(12)
Valuation adjustments and other noncontrolling interests activity				10,150		(15,873)
Payments for Repurchase of Redeemable Noncontrolling Interest	(20,871)
Excess Tax Benefit from Share-based Compensation, Financing Activities	3,936
Stock Repurchased During Period, Shares		(1,924,077)
Ending Balance at Sep. 30, 2014	$ 1,492,208	$ 1,007,764	$ (3,898)	$ 488,342	$ (451)	$ 0
Ending Balance (in shares) at Sep. 30, 2014	62,838,628	62,838,628