Consolidated Statements Of Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Noncontrolling Interests [Member]
Common Stock, Dividends, Per Share, Cash Paid	$ 0.3875
Beginning Balance (in shares) at Dec. 31, 2018		65,688,356
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued		61,576
Ending Balance (in shares) at Mar. 31, 2019		65,749,932
Beginning Balance at Dec. 31, 2018		$ 1,136,491	$ (7,866)	$ 644,595
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Equity compensation expense		4,452
Issuance of common stock, net of issuance costs		190
Payment of minimum tax withholdings for share-based payment awards		(891)
Other comprehensive income	$ 160		160
Net income attributable to Avista Corporation shareholders	115,794			115,794
Cash dividends paid (common stock)				(25,615)
Ending Balance at Mar. 31, 2019	1,868,222	$ 1,140,242	(7,706)	734,774
Beginning Balance Noncontrolling Interest at Dec. 31, 2018					$ 825
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Net income attributable to noncontrolling interests					87
Ending Balance Noncontrolling Interest at Mar. 31, 2019					912
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Total Avista Corporation shareholders’ equity	1,867,310
Total Avista Corporation shareholders’ equity	$ 1,939,284
Common Stock, Dividends, Per Share, Cash Paid	$ 0.4050
Beginning Balance (in shares) at Dec. 31, 2019	67,176,996	67,176,996
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued		115,237
Ending Balance (in shares) at Mar. 31, 2020	67,292,233	67,292,233
Beginning Balance at Dec. 31, 2019		$ 1,210,741	(10,259)	738,802
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Equity compensation expense		804
Issuance of common stock, net of issuance costs		175
Payment of minimum tax withholdings for share-based payment awards		(2,408)
Other comprehensive income	$ 205		205
Net income attributable to Avista Corporation shareholders	48,424			48,424
Cash dividends paid (common stock)				(27,389)
Ending Balance at Mar. 31, 2020	1,959,095	$ 1,209,312	$ (10,054)	$ 759,837
Beginning Balance Noncontrolling Interest at Dec. 31, 2019					0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Net income attributable to noncontrolling interests					0
Ending Balance Noncontrolling Interest at Mar. 31, 2020					$ 0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Total Avista Corporation shareholders’ equity	$ 1,959,095