CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 4,876	$ 5,090	$ 70,753	$ 145,987
Other Comprehensive Income:
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes of $58, $43, $171 and $128 respectively	220	162	645	483
Total other comprehensive income	220	162	645	483
Comprehensive income	5,096	5,252	71,398	146,470
Comprehensive loss attributable to noncontrolling interests				216
Comprehensive income attributable to Avista Corporation shareholders	$ 5,096	$ 5,252	$ 71,398	$ 146,686