Segment Reporting (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Operating revenue		$ 2,180	$ 1,939	$ 2,152
Electric fuel and purchased power		756	588	910
Operating and maintenance expenses		343	313	279
Utilities Operating Expense, Depreciation and Amortization		464	455	368
Other income (expense), net		9	12	2
Interest and Debt Expense		177	153	136
Total income tax benefit		(40)	(57)	(45)
Net Income (Loss) Attributable to Parent		$ 395	394	384
Number Of Reportable Segments, Not Disclosed, Flag		11. Segment Information
Total revenues | Regulated Electric Segment
Segment Reporting Information [Line Items]
Operating revenue		$ 2,180	1,939	2,152
Electric fuel and purchased power		756	588	910
Operating and maintenance expenses		343	313	279
Utilities Operating Expense, Depreciation and Amortization		464	455	368
Other income (expense), net	[1]	85	93	120
Interest and Debt Expense		177	153	136
Total income tax benefit		(40)	(57)	(45)
Net Income (Loss) Attributable to Parent		$ 395	$ 394	$ 384

[1] Other segment expenses, net, for 2023 additionally includes workforce reduction expenses