Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations Attributable to Parent	$ 31,254	$ 24,212	$ 78,730	$ 65,432
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	69,617	1,445	70,640	2,566
Numerator:
Net income attributable to Avista Corporation shareholders	100,871	25,657	149,370	67,998
Subsidiary earnings adjustment for dilutive securities	58	(39)	5	(82)
Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	$ 69,675	$ 1,406	$ 70,645	$ 2,484
Denominator:
Weighted-average number of common shares outstanding-basic	60,184	59,937	60,153	59,926
Performance and restricted stock awards	279	25	163	28
Weighted-average number of common shares outstanding-diluted	60,463	59,962	60,316	59,954
Earnings per common share attributable to Avista Corporation:
Basic	$ 1.68	$ 0.43	$ 2.48	$ 1.13
Diluted (usd per share)	$ 1.67	$ 0.43	$ 2.48	$ 1.13
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.52	$ 0.40	$ 1.31	$ 1.09
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	$ 1.16	$ 0.03	$ 1.17	$ 0.04
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.52	$ 0.40	$ 1.31	$ 1.09
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 1.15	$ 0.03	$ 1.17	$ 0.04