Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Electric fuel and purchased power	$ 198	$ 216
Operating and maintenance expenses	86	88
Utilities Operating Expense, Depreciation and Amortization	119	112
Other income, net	0	1
Interest and Debt Expense	46	43
Income tax benefit	(20)	(21)
Net income	$ 84	59
Number Of Reportable Segments, Disclosed By Definition, Flag	true
Total revenues | Regulated Electric Segment
Segment Reporting Information [Line Items]
Regulated Operating Revenue, Electric	$ 530	521
Electric fuel and purchased power	198	216
Operating and maintenance expenses	86	88
Utilities Operating Expense, Depreciation and Amortization	119	112
Other income, net	17	24
Interest and Debt Expense	46	43
Income tax benefit	(20)	(21)
Net income	$ 84	$ 59