CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]
Beginning Balance (in shares) at Dec. 31, 2017		65,494,333
Shares issued through equity compensation plans		185,794
Shares issued through Employee Investment Plan (401-K)		8,229
Ending Balance (in shares) at Dec. 31, 2018		65,688,356
Beginning Balance at Dec. 31, 2017		$ 1,133,448	$ (8,090)	$ 604,470
Equity compensation expense		5,765
Issuance of common stock through equity compensation plans		791
Issuance of common stock through Employee Investment Plan (401-K)		416
Payment of minimum tax withholdings for share-based payment awards		(3,929)
Ending Balance at Dec. 31, 2018	$ 1,774,045	$ 1,136,491	(7,866)	644,595
Other comprehensive income (loss)	1,966		1,966
Reclassification of excess income tax benefits			(1,742)	1,742
Net income attributable to Avista Corporation shareholders	136,429			136,429
Cash dividends paid (common stock)				(98,046)
Beginning Balance Noncontrolling Interest at Dec. 31, 2017					$ 656
Net income attributable to noncontrolling interests	$ 169
Ending Balance Noncontrolling Interest at Dec. 31, 2018					$ 825
Dividends declared per common share	$ 1.49
Total Avista Corporation shareholders’ equity	$ 1,773,220
Shares issued through equity compensation plans		75,399
Shares issued through Employee Investment Plan (401-K)		3,653
Shares issued through sales agency agreements		1,409,588
Ending Balance (in shares) at Dec. 31, 2019	67,176,996	67,176,996
Equity compensation expense		$ 10,568
Issuance of common stock through equity compensation plans		827
Issuance of common stock through Employee Investment Plan (401-K)		175
Issuance of common stock through sales agency agreements, net of issuance costs		63,571
Payment of minimum tax withholdings for share-based payment awards		(891)
Ending Balance at Dec. 31, 2019	$ 1,939,284	$ 1,210,741	(10,259)	738,802
Other comprehensive income (loss)	(2,393)		(2,393)
Net income attributable to Avista Corporation shareholders	196,979			196,979
Cash dividends paid (common stock)				(102,772)
Net income attributable to noncontrolling interests	(216)
Deconsolidation of noncontrolling interests related to sale of METALfx	$ (609)
Dividends declared per common share	$ 1.55
Total Avista Corporation shareholders’ equity	$ 1,939,284
Shares issued through equity compensation plans		139,726
Shares issued through Employee Investment Plan (401-K)		17,179
Shares issued through sales agency agreements		1,905,000
Ending Balance (in shares) at Dec. 31, 2020	69,238,901	69,238,901
Equity compensation expense		$ 5,535
Issuance of common stock through equity compensation plans		965
Issuance of common stock through Employee Investment Plan (401-K)		674
Issuance of common stock through sales agency agreements, net of issuance costs		70,561
Payment of minimum tax withholdings for share-based payment awards		(2,408)
Ending Balance at Dec. 31, 2020	$ 2,029,726	$ 1,286,068	(14,378)	758,036
Other comprehensive income (loss)	(4,119)		$ (4,119)
Net income attributable to Avista Corporation shareholders	$ 129,488			129,488
Cash dividends paid (common stock)				$ (110,254)
Dividends declared per common share	$ 1.62
Total Avista Corporation shareholders’ equity	$ 2,029,726