Consolidated Statements Of Equity And Redeemable Noncontrolling Interests - USD ($) $ in Thousands	Total	Common Stock [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]
Beginning Balance (in shares) at Dec. 31, 2016		64,187,934
Shares issued through equity compensation plans		214,925
Shares issued through Employee Investment Plan (401-K)		21,474
Shares issued through sales agency agreements		1,070,000
Ending Balance (in shares) at Dec. 31, 2017		65,494,333
Beginning Balance at Dec. 31, 2016		$ 1,075,281	$ (7,568)	$ 581,014	$ (251)
Equity compensation expense		6,530
Issuance of common stock through equity compensation plans		720
Issuance of common stock through Employee Investment Plan (401-K)		939
Issuance of common stock through sales agency agreements, net of issuance costs		54,721
Payment of minimum tax withholdings for share-based payment awards		(3,552)
Purchase of subsidiary noncontrolling interests		(1,191)			891
Other comprehensive income (loss)	$ (522)		(522)
Reclassification from AOCI to Retained Earnings			0	0
Net income attributable to Avista Corp. shareholders	115,916			115,916
Cash dividends paid (common stock)				(92,460)
Noncontrolling Interest, Decrease from Deconsolidation					0
Net income attributable to noncontrolling interests					16
Ending Balance at Dec. 31, 2017	$ 1,730,484	$ 1,133,448	(8,090)	604,470	656
Dividends declared per common share	$ 1.43
Total Avista Corporation shareholders’ equity	$ 1,729,828
Shares issued through equity compensation plans		185,794
Shares issued through Employee Investment Plan (401-K)		8,229
Shares issued through sales agency agreements		0
Ending Balance (in shares) at Dec. 31, 2018	65,688,356	65,688,356
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
Issuance of common stock through sales agency agreements, net of issuance costs		0
Payment of minimum tax withholdings for share-based payment awards		(3,929)
Purchase of subsidiary noncontrolling interests		0			0
Other comprehensive income (loss)	$ 1,966		1,966
Reclassification from AOCI to Retained Earnings			(1,742)	1,742
Net income attributable to Avista Corp. shareholders	136,429			136,429
Cash dividends paid (common stock)				(98,046)
Noncontrolling Interest, Decrease from Deconsolidation					0
Net income attributable to noncontrolling interests					169
Ending Balance at Dec. 31, 2018	$ 1,774,045	$ 1,136,491	(7,866)	644,595	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)
Purchase of subsidiary noncontrolling interests		0			0
Other comprehensive income (loss)	$ (2,393)		(2,393)
Reclassification from AOCI to Retained Earnings			0	0
Net income attributable to Avista Corp. shareholders	196,979			196,979
Cash dividends paid (common stock)				(102,772)
Noncontrolling Interest, Decrease from Deconsolidation					(609)
Net income attributable to noncontrolling interests					(216)
Ending Balance at Dec. 31, 2019	$ 1,939,284	$ 1,210,741	$ (10,259)	$ 738,802	$ 0
Dividends declared per common share	$ 1.55
Total Avista Corporation shareholders’ equity	$ 1,939,284