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
Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income from continuing operations attributable to Avista Corp. shareholders	$ 115,794	$ 54,890
Denominator:
Weighted-average number of common shares outstanding-basic	65,733	65,639
Performance and restricted stock awards	208	292
Weighted-average number of common shares outstanding-diluted	65,941	65,931
Earnings Per Share, Basic [Abstract]
Basic	$ 1.76	$ 0.84
Earnings Per Share, Diluted [Abstract]
Diluted	$ 1.76	$ 0.83

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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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