Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator:
Net income attributable to Avista Corporation shareholders	$ 48,499	$ 42,341
Subsidiary earnings adjustment for dilutive securities	(53)	(43)
Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	$ 48,446	$ 42,298
Denominator:
Weighted-average number of common shares outstanding-basic	60,122	59,866
Performance and restricted stock awards	46	32
Weighted-average number of common shares outstanding-diluted	60,168	59,898
Earnings per common share attributable to Avista Corporation:
Basic	$ 0.81	$ 0.71
Diluted (usd per share)	$ 0.81	$ 0.71