Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Income (Loss) from Continuing Operations Attributable to Parent	$ 137,228	$ 118,080	$ 119,817
Operating Revenues:
Utility revenues	1,418,914	1,456,091	1,433,343
Non-utility revenues	23,569	28,685	39,219
Total operating revenues	1,442,483	1,484,776	1,472,562
Utility operating expenses:
Resource costs	551,366	656,964	678,244
Other operating expenses	315,795	303,221	286,832
Depreciation and amortization	160,514	143,499	129,570
Taxes other than income taxes	98,735	97,657	94,300
Non-utility operating expenses:
Other operating expenses	25,501	29,526	30,418
Depreciation, Depletion and Amortization, Nonproduction	769	695	610
Total operating expenses	1,152,680	1,231,562	1,219,974
Income from operations	289,803	253,214	252,588
Interest expense	86,496	79,968	75,302
Interest expense to affiliated trusts	634	473	450
Public Utilities, Allowance for Funds Used During Construction, Additions	(2,651)	(3,546)	(3,924)
Other income-net	(10,078)	(9,300)	(11,346)
Income from continuing operations before income taxes	215,402	185,619	192,106
Income tax expense	78,086	67,449	72,240
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	137,316	118,170	119,866
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0	5,147	72,224
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0	5,147	72,411
Net income from continuing operations	137,316	123,317	192,277
Net income attributable to noncontrolling interests	(88)	(90)	(236)
Net income attributable to Avista Corp. shareholders	$ 137,228	$ 123,227	$ 192,041
Weighted-average common shares outstanding (thousands), basic	63,508	62,301	61,632
Weighted-average common shares outstanding (thousands), diluted	63,920	62,708	61,887
Income (Loss) from Continuing Operations, Per Basic Share	$ 2.16	$ 1.90	$ 1.94
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0.00	0.08	1.18
Earnings per common share attributable to Avista Corporation shareholders:
Earnings Per Share, Basic	2.16	1.98	3.12
Earnings Per Share, Diluted	2.15	1.97	3.10
Income (Loss) from Continuing Operations, Per Diluted Share	2.15	1.89	1.93
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0.00	0.08	1.17
Dividends declared per common share	$ 1.37	$ 1.32	$ 1.27