Information by Business Segments - Schedule of Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Operating revenues	$ 402,072	$ 379,937	$ 1,011,488	$ 854,568
Resource costs	144,326	141,244	437,443	334,172
Other operating expenses	109,949	103,820	221,514	209,809
Depreciation and amortization	67,831	66,148	135,761	131,367
Income (loss) from operations	54,256	43,808	155,372	120,409
Interest expense	36,580	35,626	74,141	71,281
Income tax expense (benefit)	495	(5,810)	2,801	(12,438)
Net income (loss)	22,858	17,484	94,353	72,329
Capital expenditures	132,498	126,256	251,207	226,749
Total Assets	7,683,770		7,683,770		$ 7,702,477
Operating Segments [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	402,032	379,798	1,011,426	854,303
Resource costs	144,326	141,244	437,443	334,172
Other operating expenses	109,591	103,071	220,840	208,049
Depreciation and amortization	67,829	66,148	135,756	131,336
Income (loss) from operations	54,576	44,418	155,989	121,935
Interest expense	36,450	35,496	73,881	71,022
Income tax expense (benefit)	1,088	(5,083)	3,375	(11,492)
Net income (loss)	25,044	20,169	96,463	75,838
Capital expenditures	132,498	126,256	251,207	226,746
Total Assets	7,514,764		7,514,764		7,532,387
Operating Segments [Member] | Avista Utilities [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	390,814	368,604	985,750	828,746
Resource costs	143,125	140,017	435,633	332,154
Other operating expenses	105,532	99,276	212,847	200,665
Depreciation and amortization	64,973	63,419	130,058	125,883
Income (loss) from operations	51,752	41,257	146,389	111,816
Interest expense	35,035	34,044	71,066	68,118
Income tax expense (benefit)	714	(5,556)	1,514	(13,504)
Net income (loss)	23,935	18,810	91,443	70,437
Capital expenditures	127,916	121,834	245,160	219,598
Total Assets	7,240,803		7,240,803		7,262,704
Operating Segments [Member] | Alaska Electric Light & Power [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	11,218	11,194	25,676	25,557
Resource costs	1,201	1,227	1,810	2,018
Other operating expenses	4,059	3,795	7,993	7,384
Depreciation and amortization	2,856	2,729	5,698	5,453
Income (loss) from operations	2,824	3,161	9,600	10,119
Interest expense	1,415	1,452	2,815	2,904
Income tax expense (benefit)	374	473	1,861	2,012
Net income (loss)	1,109	1,359	5,020	5,401
Capital expenditures	4,582	4,422	6,047	7,148
Total Assets	273,961		273,961		269,683
Other [Member] | Non-Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	40	139	62	265
Resource costs	0	0	0	0
Other operating expenses	358	749	674	1,760
Depreciation and amortization	2	0	5	31
Income (loss) from operations	(320)	(610)	(617)	(1,526)
Interest expense	642	448	1,212	795
Income tax expense (benefit)	(593)	(727)	(574)	(946)
Net income (loss)	(2,186)	(2,685)	(2,110)	(3,509)
Capital expenditures	0	0	0	3
Total Assets	194,145		194,145		191,665
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
Resource costs	0	0	0	0
Other operating expenses	0	0	0	0
Depreciation and amortization	0	0	0	0
Income (loss) from operations	0	0	0	0
Interest expense	(512)	(318)	(952)	(536)
Income tax expense (benefit)	0	0	0	0
Net income (loss)	0	0	0	0
Capital expenditures	0	$ 0	0	$ 0
Total Assets	$ (25,139)		$ (25,139)		$ (21,575)