Other Income Tax Matters (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021		Dec. 31, 2020
Income Tax [Line Items]
Federal NOL carryforward		$ 8	$ 336
Federal tax credit carryforwards		294	187
State NOL carryforwards		$ 4	$ 111
Federal statutory rate		21.00%	21.00%	[1]	21.00%	[1]
State income tax on pretax income, net of federal tax effect		2.30%	2.50%	[1]	2.30%	[1]
Effective Income Tax Rate Reconciliation, Tax Credit, Percent	[2]	(35.90%)	(39.70%)	[1]	(18.30%)	[1]
Plant regulatory differences (b)	[3]	(3.80%)	(4.80%)	[1]	(6.40%)	[1]
Amortization of excess nonplant deferred taxes		(0.90%)	(1.10%)	[1]	(0.80%)	[1]
Other, net		(0.60%)	(0.70%)	[1]	(1.30%)	[1]
Effective income tax rate		(17.90%)	(22.80%)	[1]	(3.50%)	[1]
Total income tax benefit		$ (53)	$ (59)		$ (10)
Deferred tax expense (benefit) excluding items below		37	(23)		53
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities		(20)	(24)		(31)
Total deferred tax assets		(17)	(47)		(22)
Deferred fuel costs		35	34	[4]
Operating lease liabilities		434
NOL carryforward		2	76	[4]
income tax expense [Member]
Income Tax [Line Items]
Current federal tax benefit		(65)	(11)		(31)
Current state tax benefit		(5)	(1)		(1)
Deferred federal tax expense (benefit)		3	(57)		13
Deferred state tax expense		13	9		8
Deferred change in unrecognized tax expense		1	1		1
Total income tax benefit		(53)	(59)		$ (10)
Net Deferred Tax Liablility [Member]
Income Tax [Line Items]
Federal tax credit carryforwards		294	187	[4]
Total deferred tax assets		(503)	(477)	[4]
Differences between book and tax bases of property		1,015	942	[4]
Operating lease assets		97	103	[4]
Regulatory assets		61	65	[4]
Pension expense		33	34	[4]
Other		1	1	[4]
Total deferred tax liabilities		1,242	1,179	[4]
Operating lease liabilities		97	103	[4]
Regulatory liabilities		98	98	[4]
Other employee benefits		6	7	[4]
Other		6	6	[4]
Net deferred tax liability		$ 739	$ 702	[4]

[1] Prior period amounts have been restated to conform to current year presentation.

[2] Wind PTCs are credited to customers (reduction to revenue) and do not materially impact net income.

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

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