CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 17,453	$ 25,016	$ 65,877	$ 140,897
Other Comprehensive Income:
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes of $59, $42, $113 and $85 respectively	220	161	425	321
Total other comprehensive income	220	161	425	321
Comprehensive income	17,673	25,177	66,302	141,218
Comprehensive loss attributable to noncontrolling interests		303		216
Comprehensive income attributable to Avista Corporation shareholders	$ 17,673	$ 25,480	$ 66,302	$ 141,434