Other Income Tax Matters (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax [Line Items]
Federal tax credit carryforwards		$ 292	$ 406
State NOL carryforwards		$ 2	$ 3
Federal statutory rate		21.00%	21.00%	21.00%
State income tax on pretax income, net of federal tax effect		2.10%	2.40%	2.30%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	[1]	(34.30%)	(33.50%)	(35.90%)
Plant regulatory differences (b)	[2]	(4.60%)	(3.30%)	(3.80%)
Amortization of (excess)/deficient nonplant deferred taxes		(0.20%)	0.30%	(0.90%)
Other, net		(0.90%)	(0.20%)	(0.60%)
Effective income tax rate		(16.90%)	(13.30%)	(17.90%)
Total income tax benefit		$ (57)	$ (45)	$ (53)
Deferred tax expense (benefit) excluding items below		143	(117)	37
Adjustments to deferred income taxes for wind production tax credit (a)	[3]	(226)	0	0
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities		(19)	(16)	(20)
Tax credit carryforward		371
Income Tax Expense (Benefit), Intraperiod Tax Allocation		(1)	0	0
Tax Credit Carryforward, Valuation Allowance		0	(2)
Total deferred tax assets		(103)	(133)	(17)
income tax expense [Member]
Income Tax [Line Items]
Current federal tax expense (benefit)		42	76	(65)
Current state tax expense (benefit)		4	12	(5)
Deferred federal tax (benefit) expense		(105)	(132)	3
Deferred state tax expense (benefit)		2	(1)	13
Deferred change in unrecognized tax expense		0	0	1
Total income tax benefit		(57)	(45)	$ (53)
Net Deferred Tax Liablility [Member]
Income Tax [Line Items]
Federal tax credit carryforwards		292	406
Differences between book and tax bases of property		1,089	1,072
Operating lease assets		83	90
Regulatory assets		53	51
Deferred tax liability - Pension expense		33	32
Total deferred tax liabilities		1,260	1,245
Regulatory liabilities		90	95
other employee benefits		5	6
Deferred Fuel Cost		10	5
Other		15	23
Operating lease liabilities		83	90
Tax Credit Carryforward, Valuation Allowance		0	(2)
Total deferred tax assets		(495)	(623)
Net deferred tax liability		765	622
Net Deferred Tax Liability
Income Tax [Line Items]
Deferred Tax Assets, Tax Deferred Expense, Other		$ 2	$ 0

[1] Wind PTCs net of estimated transfer discounts. Gross wind PTCs are credited to customers (reduction to revenue) and do not materially impact net income.

[2] Plant regulatory differences primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit are offset by corresponding revenue reductions.

[3] Proceeds from tax credit transfers are included in cash received (paid) for income taxes in the statement of cash flows.