Other Income Tax Matters (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021
Income Tax [Line Items]
Federal NOL carryforward		$ 0	$ 8
Federal tax credit carryforwards		406	294
State NOL carryforwards		$ 3	$ 4
Federal statutory rate		21.00%	21.00%		21.00%
State income tax on pretax income, net of federal tax effect		2.40%	2.30%		2.50%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	[1]	(33.50%)	(35.90%)		(39.70%)
Plant regulatory differences (b)	[2]	(3.30%)	(3.80%)		(4.80%)
Amortization of deficient/(excess) nonplant deferred taxes		0.30%	(0.90%)		(1.10%)
Other, net		(0.20%)	(0.60%)		(0.70%)
Effective income tax rate		(13.30%)	(17.90%)		(22.80%)
Total income tax benefit		$ (45)	$ (53)		$ (59)
Deferred tax (benefit) expense excluding items below		(117)	37		(23)
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities		(16)	(20)		(24)
Total deferred tax assets		133	17		47
Tax credit carryforward		403
Tax Credit Carryforward, Valuation Allowance		(2)	0
income tax expense [Member]
Income Tax [Line Items]
Current federal tax expense (benefit)		76	(65)		(11)
Current state tax expense (benefit)		12	(5)		(1)
Deferred federal tax (benefit) expense		(132)	3		(57)
Deferred state tax (benefit) expense		(1)	13		9
Deferred change in unrecognized tax expense		0	1		1
Total income tax benefit		(45)	(53)		$ (59)
Net Deferred Tax Liablility [Member]
Income Tax [Line Items]
Federal tax credit carryforwards		406	294	[3]
Total deferred tax assets		623	467	[3]
Differences between book and tax bases of property		1,072	1,015	[3]
Operating lease assets		90	97	[3]
Regulatory assets		51	61	[3]
Total deferred tax liabilities		1,245	1,206	[3]
Regulatory liabilities		95	98	[3]
Deferred Fuel Cost		(5)	(35)	[3]
other employee benefits		6	6	[3]
Other		23	5	[3]
Net deferred tax liability		622	739	[3]
Operating lease liabilities		90	97	[3]
Operating Loss Carryforwards		0	2	[3]
Tax Credit Carryforward, Valuation Allowance		(2)	0	[3]
Deferred tax liability - Pension expense		$ 32	$ 33	[3]

[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] Prior periods have been reclassified to conform to current year presentation.