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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income from continuing operations attributable to Avista Corp. shareholders	$ 12,234	$ 12,722	$ 97,137	$ 84,221
Net income from discontinued operations attributable to Avista Corp. shareholders	$ 0	$ 289	$ 0	$ 485
Denominator:
Weighted-average number of common shares outstanding-basic	63,857	62,299	63,282	62,299
Performance and restricted stock awards	468	389	405	392
Weighted-average number of common shares outstanding-diluted	64,325	62,688	63,687	62,691
Earnings Per Share, Basic [Abstract]
Earnings per common share from continuing operations	$ 0.19	$ 0.21	$ 1.53	$ 1.35
Earnings per common share from discontinued operations	0.00	0.00	0.00	0.01
Basic	0.19	0.21	1.53	1.36
Earnings Per Share, Diluted [Abstract]
Earnings per common share from continuing operations	0.19	0.21	1.53	1.34
Earnings per common share from discontinued operations	0.00	0.00	0.00	0.01
Diluted (usd per share)	$ 0.19	$ 0.21	$ 1.53	$ 1.35