Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations Attributable to Parent	$ 12,722	$ 10,506	$ 84,221	$ 89,236
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	289	(55)	485	70,585
Numerator:
Net income attributable to Avista Corporation shareholders	13,011	10,451	84,706	159,821
Subsidiary earnings adjustment for dilutive securities	0	0	0	5
Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	$ 289	$ (55)	$ 485	$ 70,590
Denominator:
Weighted-average number of common shares outstanding-basic	62,299	63,934	62,299	61,413
Performance and restricted stock awards	389	310	392	212
Weighted-average number of common shares outstanding-diluted	62,688	64,244	62,691	61,625
Earnings per common share attributable to Avista Corporation:
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.21	$ 0.16	$ 1.35	$ 1.45
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0.00	0.00	0.01	1.15
Basic	0.21	0.16	1.36	2.60
Income (Loss) from Continuing Operations, Per Diluted Share	0.21	0.16	1.34	1.45
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0.00	0.00	0.01	1.14
Diluted (usd per share)	$ 0.21	$ 0.16	$ 1.35	$ 2.59