Information by Business Segments - Schedule of Business Segments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 462,046	$ 412,870
Resource costs	186,868	134,579
Other operating expenses	95,483	88,739
Depreciation and amortization	62,609	55,348
Income (loss) from operations	82,969	101,895
Interest expense	28,184	26,413
Income taxes	(10,836)	12,164
Net income (loss)	71,565	68,017
Capital expenditures	96,401	97,231
Total Assets	7,036,010		$ 6,853,583
Avista Utilities [Member]
Segment Reporting Information [Line Items]
Operating revenues	448,872	399,860
Alaska Electric Light & Power [Member]
Segment Reporting Information [Line Items]
Operating revenues	13,054	12,821
Operating Segments [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	461,926	412,681
Resource costs	186,868	134,579
Other operating expenses	94,527	87,555
Depreciation and amortization	62,577	55,221
Income (loss) from operations	83,837	103,017
Interest expense	28,059	26,325
Income taxes	(11,100)	12,051
Net income (loss)	70,571	67,534
Capital expenditures	95,987	97,203
Total Assets	6,904,270		6,723,666
Operating Segments [Member] | Avista Utilities [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	448,872	399,860
Resource costs	186,424	133,840
Other operating expenses	90,984	84,599
Depreciation and amortization	59,879	52,724
Income (loss) from operations	77,779	96,693
Interest expense	26,572	24,800
Income taxes	(12,360)	10,718
Net income (loss)	67,278	64,058
Capital expenditures	95,464	96,394
Total Assets	6,636,604		6,458,244
Operating Segments [Member] | Alaska Electric Light & Power [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	13,054	12,821
Resource costs	444	739
Other operating expenses	3,543	2,956
Depreciation and amortization	2,698	2,497
Income (loss) from operations	6,058	6,324
Interest expense	1,487	1,525
Income taxes	1,260	1,333
Net income (loss)	3,293	3,476
Capital expenditures	523	809
Total Assets	267,666		265,422
Other [Member] | Non-Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	120	189
Resource costs	0	0
Other operating expenses	956	1,184
Depreciation and amortization	32	127
Income (loss) from operations	(868)	(1,122)
Interest expense	128	129
Income taxes	264	113
Net income (loss)	994	483
Capital expenditures	414	28
Total Assets	133,220		132,158
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Resource costs	0	0
Other operating expenses	0	0
Depreciation and amortization	0	0
Income (loss) from operations	0	0
Interest expense	(3)	(41)
Income taxes	0	0
Net income (loss)	0	0
Capital expenditures	0	$ 0
Total Assets	$ (1,480)		$ (2,241)