Business Acquisitions (Tables)

3 Months Ended

Mar. 31, 2015

Business Acquisition [Line Items]

Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable [Table Text Block]

	July 1, 2014
Contract acquisition price (using the calculated $32.46 per share common stock price)
Gross contract price	$	170,000
Acquired cash	19,704
Acquired debt (excluding capital lease obligation)	(38,832		)
Other closing adjustments	(58		)
Total adjusted contract price	$	150,814
Fair value of consideration transferred
Avista Corp. common stock (4,500,014 shares at $33.35 per share)	$	150,075
Avista Corp. common stock (1,427 shares at $30.71 per share)	44
Cash	4,697
Fair value of total consideration transferred	$	154,816

Business Acquisition, Pro Forma Information [Table Text Block]

	Actual		Pro forma
	2015		2014
Actual Avista Corp. revenues from continuing operations (excluding AERC)	$	433,699	$	446,578
Supplemental pro forma AERC revenues (1)	12,791		13,186
Total pro forma revenues	446,490		459,764
Actual AERC revenues included in Avista Corp. revenues (1)	12,791		—
Actual Avista Corp. net income from continuing operations attributable to Avista Corp. shareholders (excluding AERC)	43,918		47,476
Actual Avista Corp. net income from discontinued operations attributable to Avista Corp. shareholders	—		1,023
Adjustment to Avista Corp.'s net income for acquisition costs (net of tax) (2)	5		294
Supplemental pro forma AERC net income (1)	2,531		3,256
Total pro forma net income	46,454		52,049
Actual AERC net income included in Avista Corp. net income (1)	$	2,531	$	—