Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 192,277	$ 112,294	$ 78,800
Other Comprehensive Income (Loss):
Unrealized investment gains/(losses) - net of taxes of $664, $(1,026) and $191, respectively	1,126	(1,741)	323
Reclassification adjustment for realized gains on investment securities included in net income - net of taxes of $(1), $(7) and $(171), respectively	(2)	(12)	(290)
Reclassification adjustment for realized losses on investments, Net of Tax	462	0	0
Change in unfunded benefit obligation for pension and other postretirement benefit plans - net of taxes of $(1,967), $1,418 and $(590), respectively	(3,655)	2,634	(1,096)
Total other comprehensive income (loss)	(2,069)	881	(1,063)
Comprehensive income	190,208	113,175	77,737
Comprehensive income attributable to noncontrolling interests	(236)	(1,217)	(590)
Comprehensive income attributable to Avista Corporation shareholders	$ 189,972	$ 111,958	$ 77,147