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Common Stock Common Stock (Notes) | 3 Months Ended
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Mar. 31, 2018
Stockholders' Equity Note [Abstract] |
Stockholders' Equity Note Disclosure [Text Block] | COMMON STOCK The Company has entered into four separate sales agency agreements under which Avista Corp.'s sales agents may offer and sell up to 3.8 million new shares of Avista Corp.'s common stock, no par value, from time to time. The sales agency agreements expire on February 29, 2020 and as of March 31, 2018, the Company has 1.1 million shares remaining to be issued under these agreements. No shares were issued under these agreements in the three months ended March 31, 2018.

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- Definition The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -URI http://asc.fasb.org/topic&trid=2208762 + Details
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