CONDENSED 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, 2018		65,688,356
Shares issued		422,961
Ending Balance (in shares) at Jun. 30, 2019		66,111,317
Beginning Balance at Dec. 31, 2018		$ 1,136,491	$ (7,866)	$ 644,595
Equity compensation expense		6,495
Issuance of common stock, net of issuance costs		14,929
Payment of minimum tax withholdings for share-based payment awards		(891)
Ending Balance at Jun. 30, 2019	$ 1,884,034	$ 1,157,024	(7,545)	734,555
Other comprehensive income	321		321
Net income attributable to Avista Corporation shareholders	141,113			141,113
Cash dividends paid on common stock				(51,153)
Beginning Balance Noncontrolling Interest at Dec. 31, 2018					$ 825
Net loss attributable to noncontrolling interests	(216)
Deconsolidation of noncontrolling interests related to sale of METALfx	$ (609)
Dividends declared per common share	$ 0.7750
Beginning Balance (in shares) at Mar. 31, 2019		65,749,932
Shares issued		361,385
Ending Balance (in shares) at Jun. 30, 2019		66,111,317
Beginning Balance at Mar. 31, 2019		$ 1,140,242	(7,706)	734,774
Equity compensation expense		2,043
Issuance of common stock, net of issuance costs		14,739
Ending Balance at Jun. 30, 2019	$ 1,884,034	$ 1,157,024	(7,545)	734,555
Other comprehensive income	161		161
Net income attributable to Avista Corporation shareholders	25,319			25,319
Cash dividends paid on common stock				(25,538)
Beginning Balance Noncontrolling Interest at Mar. 31, 2019					$ 912
Net loss attributable to noncontrolling interests	(303)
Deconsolidation of noncontrolling interests related to sale of METALfx	$ (609)
Dividends declared per common share	$ 0.3875
Total Avista Corporation shareholders’ equity	$ 1,884,034
Total Avista Corporation shareholders’ equity	$ 1,939,284
Beginning Balance (in shares) at Dec. 31, 2019	67,176,996	67,176,996
Shares issued		736,269
Ending Balance (in shares) at Jun. 30, 2020	67,913,265	67,913,265
Beginning Balance at Dec. 31, 2019		$ 1,210,741	(10,259)	738,802
Equity compensation expense		2,678
Issuance of common stock, net of issuance costs		23,890
Payment of minimum tax withholdings for share-based payment awards		(2,408)
Ending Balance at Jun. 30, 2020	$ 1,975,038	$ 1,234,901	(9,834)	749,971
Other comprehensive income	425		425
Net income attributable to Avista Corporation shareholders	$ 65,877			65,877
Cash dividends paid on common stock				(54,708)
Dividends declared per common share	$ 0.8100
Beginning Balance (in shares) at Mar. 31, 2020		67,292,233
Shares issued		621,032
Ending Balance (in shares) at Jun. 30, 2020	67,913,265	67,913,265
Beginning Balance at Mar. 31, 2020		$ 1,209,312	(10,054)	759,837
Equity compensation expense		1,874
Issuance of common stock, net of issuance costs		23,715
Ending Balance at Jun. 30, 2020	$ 1,975,038	$ 1,234,901	(9,834)	749,971
Other comprehensive income	220		$ 220
Net income attributable to Avista Corporation shareholders	$ 17,453			17,453
Cash dividends paid on common stock				$ (27,319)
Dividends declared per common share	$ 0.4050
Total Avista Corporation shareholders’ equity	$ 1,975,038