Information by Business Segments - Schedule of Business Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Operating revenues	$ 411	$ 402	$ 1,028	$ 1,011
Resource costs	130	144	386	437
Other operating expenses	124	109	253	221
Depreciation and amortization	72	68	143	136
Interest income	3	3	5	8
Interest expense	37	37	76	74
Other segment expenses	36	23	69	54
Income tax expense (benefit)	1	1	13	3
Net income (loss)	14	23	93	94
Capital expenditures	143	133	246	251
Total Assets	8,065		8,065		$ 7,941
Operating Segments [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	411	402	1,028	1,011
Resource costs	130	144	386	437
Other operating expenses	124	109	252	221
Depreciation and amortization	72	68	143	136
Interest income	3	4	6	9
Interest expense	36	37	75	74
Other segment expenses	25	22	57	53
Income tax expense (benefit)	3	1	16	3
Net income (loss)	24	25	105	96
Capital expenditures	143	133	246	251
Total Assets	7,912		7,912		7,777
Operating Segments [Member] | Avista Utilities [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	400	391	1,004	986
Resource costs	129	143	385	436
Other operating expenses	120	105	244	213
Depreciation and amortization	69	65	137	130
Interest income	3	4	6	9
Interest expense	35	35	72	71
Other segment expenses	24	22	57	53
Income tax expense (benefit)	3	1	14	1
Net income (loss)	23	24	101	91
Capital expenditures	136	128	236	245
Total Assets	7,623		7,623		7,494
Operating Segments [Member] | Alaska Electric Light & Power [Member] | Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	11	11	24	25
Resource costs	1	1	1	1
Other operating expenses	4	4	8	8
Depreciation and amortization	3	3	6	6
Interest income	0	0	0	0
Interest expense	1	2	3	3
Other segment expenses	1	0	0	0
Income tax expense (benefit)	0	0	2	2
Net income (loss)	1	1	4	5
Capital expenditures	7	5	10	6
Total Assets	289		289		283
Other Non-Reportable Segment Items [Member] | Non-Utility Revenue [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0	0
Resource costs	0	0	0	0
Other operating expenses	0	0	1	0
Depreciation and amortization	0	0	0	0
Interest income	0	0	0	0
Interest expense	1	1	2	1
Other segment expenses	11	1	12	1
Income tax expense (benefit)	(2)	0	(3)	0
Net income (loss)	(10)	(2)	(12)	(2)
Capital expenditures	0	0	0	0
Total Assets	184		184		194
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
Interest income	0	(1)	(1)	(1)
Interest expense	0	(1)	(1)	(1)
Other segment expenses	0	0	0	0
Income tax expense (benefit)	0	0	0	0
Net income (loss)	0	0	0	0
Capital expenditures	0	$ 0	0	$ 0
Total Assets	$ (31)		$ (31)		$ (30)