Information by Business Segments - Schedule of Business Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Operating revenues	$ 617	$ 609
Resource costs	256	294
Other operating expenses	129	111
Depreciation and amortization	71	68
Interest income	2	4
Interest expense	39	38
Other segment expenses (income)	32	29
Income tax expense (benefit)	12	2
Net income (loss)	79	71
Capital expenditures	103	119
Total Assets	7,966		$ 7,941
Operating Segments [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	617	609
Resource costs	256	294
Other operating expenses	128	111
Depreciation and amortization	71	68
Interest income	3	4
Interest expense	39	37
Other segment expenses (income)	30	30
Income tax expense (benefit)	13	2
Net income (loss)	82	71
Capital expenditures	103	119
Total Assets	7,804		7,777
Operating Segments [Member] | Avista Utilities [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	604	595
Resource costs	256	293
Other operating expenses	124	107
Depreciation and amortization	68	65
Interest income	3	4
Interest expense	37	36
Other segment expenses (income)	32	30
Income tax expense (benefit)	11	1
Net income (loss)	78	67
Capital expenditures	100	117
Total Assets	7,519		7,494
Operating Segments [Member] | Alaska Electric Light & Power [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	13	14
Resource costs	0	1
Other operating expenses	4	4
Depreciation and amortization	3	3
Interest income	0	0
Interest expense	2	1
Other segment expenses (income)	(2)	0
Income tax expense (benefit)	2	1
Net income (loss)	4	4
Capital expenditures	3	2
Total Assets	285		283
Other Non-Reportable Segment Items [Member] | Non-Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0
Resource costs	0	0
Other operating expenses	1	0
Depreciation and amortization	0	0
Interest income	0	0
Interest expense	1	1
Other segment expenses (income)	2	(1)
Income tax expense (benefit)	(1)	0
Net income (loss)	(3)	0
Capital expenditures	0	0
Total Assets	192		194
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
Interest income	(1)	0
Interest expense	(1)	0
Other segment expenses (income)	0	0
Income tax expense (benefit)	0	0
Net income (loss)	0	0
Capital expenditures	0	$ 0
Total Assets	$ (30)		$ (30)