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		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations Attributable to Parent	$ 10,506	$ 8,450	$ 89,236	$ 73,882
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(55)	2,963	70,585	5,529
Numerator:
Net income attributable to Avista Corporation shareholders	10,451	11,413	159,821	79,411
Subsidiary earnings adjustment for dilutive securities	0	(81)	5	(163)
Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	$ (55)	$ 2,882	$ 70,590	$ 5,366
Denominator:
Weighted-average number of common shares outstanding-basic	63,934	59,994	61,413	59,933
Performance and restricted stock awards	310	38	212	31
Weighted-average number of common shares outstanding-diluted	64,244	60,032	61,625	59,964
Earnings per common share attributable to Avista Corporation:
Basic	$ 0.16	$ 0.19	$ 2.60	$ 1.32
Diluted (usd per share)	$ 0.16	$ 0.19	$ 2.59	$ 1.32
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.16	$ 0.14	$ 1.45	$ 1.23
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	$ 0.00	$ 0.05	$ 1.15	$ 0.09
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.16	$ 0.14	$ 1.45	$ 1.23
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.00	$ 0.05	$ 1.14	$ 0.09