Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Income (Loss) from Continuing Operations Attributable to Parent	$ 118,080	$ 119,817	$ 104,273
Operating Revenues:
Utility revenues	1,456,091	1,433,343	1,402,195
Non-utility revenues	28,685	39,219	39,549
Total operating revenues	1,484,776	1,472,562	1,441,744
Utility operating expenses:
Resource costs	656,964	678,244	689,586
Other operating expenses	303,221	286,832	276,228
Depreciation and amortization	143,499	129,570	117,174
Taxes other than income taxes	97,657	94,300	88,435
Non-utility operating expenses:
Other operating expenses	29,526	30,418	38,651
Depreciation, Depletion and Amortization, Nonproduction	695	610	581
Total operating expenses	1,231,562	1,219,974	1,210,655
Income from operations	253,214	252,588	231,089
Interest expense	79,968	75,302	77,118
Interest expense to affiliated trusts	473	450	467
Public Utilities, Allowance for Funds Used During Construction, Additions	(3,546)	(3,924)	(3,676)
Other income-net	(9,300)	(11,346)	(5,167)
Income from continuing operations before income taxes	185,619	192,106	162,347
Income tax expense	67,449	72,240	58,014
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	118,170	119,866	104,333
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	5,147	72,224	6,804
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	5,147	72,411	7,961
Net income from continuing operations	123,317	192,277	112,294
Net income attributable to noncontrolling interests	(90)	(236)	(1,217)
Net income attributable to Avista Corp. shareholders	$ 123,227	$ 192,041	$ 111,077
Weighted-average common shares outstanding (thousands), basic	62,301	61,632	59,960
Weighted-average common shares outstanding (thousands), diluted	62,708	61,887	59,997
Income (Loss) from Continuing Operations, Per Basic Share	$ 1.90	$ 1.94	$ 1.74
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0.08	1.18	0.11
Earnings per common share attributable to Avista Corporation shareholders:
Earnings Per Share, Basic	1.98	3.12	1.85
Earnings Per Share, Diluted	1.97	3.10	1.85
Income (Loss) from Continuing Operations, Per Diluted Share	1.89	1.93	1.74
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ 0.08	$ 1.17	$ 0.11