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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income from continuing operations attributable to Avista Corp. shareholders	$ 25,319	$ 25,577	$ 141,113	$ 80,467
Denominator:
Weighted-average number of common shares outstanding-basic	65,894	65,677	65,814	65,658
Performance and restricted stock awards	69	306	69	299
Weighted-average number of common shares outstanding-diluted	65,963	65,983	65,883	65,957
Earnings Per Share, Basic [Abstract]
Basic	$ 0.38	$ 0.39	$ 2.14	$ 1.23
Earnings Per Share, Diluted [Abstract]
Diluted	$ 0.38	$ 0.39	$ 2.14	$ 1.22