Earnings Per Common Share Attributable to Avista Corporation Shareholders - Schedule of Computation of Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net income attributable to Avista Corp. shareholders	$ 147,334	$ 129,488	$ 196,979
Denominator:
Weighted-average number of common shares outstanding-basic	69,951	67,962	66,205
Effect of dilutive securities:
Performance and restricted stock awards	134	140	124
Weighted-average number of common shares outstanding-diluted	70,085	68,102	66,329
Earnings per common share attributable to Avista Corp. shareholders:
Basic	$ 2.11	$ 1.91	$ 2.98
Diluted	$ 2.10	$ 1.90	$ 2.97