Earnings Per Share Attributable To Avista Corporation (Computation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income from continuing operations attributable to Avista Corp. shareholders	$ 21,771	$ 27,254	$ 83,887	$ 84,903
Denominator:
Weighted-average number of common shares outstanding-basic	64,401	63,386	64,382	62,995
Performance and restricted stock awards	152	397	129	373
Weighted-average number of common shares outstanding-diluted	64,553	63,783	64,511	63,368
Earnings Per Share, Basic [Abstract]
Basic	$ 0.34	$ 0.43	$ 1.30	$ 1.35
Earnings Per Share, Diluted [Abstract]
Diluted	$ 0.34	$ 0.43	$ 1.30	$ 1.34

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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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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount after tax of income (loss) from continuing operations attributable to the parent.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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