Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 196,763	$ 136,598	$ 115,932
Other Comprehensive Income (Loss):
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes of $(636), $523 and $(281), respectively	(2,393)	1,966	(522)
Total other comprehensive income (loss)	(2,393)	1,966	(522)
Comprehensive income	194,370	138,564	115,410
Comprehensive loss (income) attributable to noncontrolling interests	216	(169)	(16)
Comprehensive income attributable to Avista Corporation shareholders	$ 194,586	$ 138,395	$ 115,394