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, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations Attributable to Parent	$ 46,449	$ 47,476
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	1,023
Numerator:
Net income attributable to Avista Corporation shareholders	46,449us-gaap_NetIncomeLoss	48,499us-gaap_NetIncomeLoss
Subsidiary earnings adjustment for dilutive securities	0us-gaap_DilutiveSecurities	(53)us-gaap_DilutiveSecurities
Adjusted net income attributable to Avista Corporation shareholders for computation of diluted earnings per common share	$ 0	$ 970
Denominator:
Weighted-average number of common shares outstanding-basic	62,318	60,122
Performance and restricted stock awards	571	46
Weighted-average number of common shares outstanding-diluted	62,889	60,168
Earnings per common share attributable to Avista Corporation:
Basic	$ 0.75us-gaap_EarningsPerShareBasic	$ 0.81us-gaap_EarningsPerShareBasic
Diluted (usd per share)	$ 0.74us-gaap_EarningsPerShareDiluted	$ 0.81us-gaap_EarningsPerShareDiluted
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.75	$ 0.79
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	$ 0.00	$ 0.02
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.74	$ 0.79
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.00	$ 0.02

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Income (Loss) from Discontinued Operations, Net of Tax, Available to Common Stockholders, Diluted

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Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise stock options, restrictive stock units (RSUs), convertible preferred stock of an employee stock ownership plan (ESOP), and other dilutive convertible securities.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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Per basic share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.

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