Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Condensed Consolidated Statements Of Comprehensive Income [Abstract]
Net income	$ 38,213	$ 42,403
Other Comprehensive Income (Loss):
Unrealized investment gains - net of taxes of $39	69
Reclassification adjustment for realized gains on investment securities included in net income - net of taxes of $(5)	(11)
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes of $82 and $(106), respectively	153	(196)
Total other comprehensive income (loss)	211	(196)
Comprehensive income	38,424	42,207
Comprehensive loss (income) attributable to noncontrolling interests	175	(485)
Comprehensive income attributable to Avista Corporation	$ 38,599	$ 41,722