Other Income Tax Matters (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021		Dec. 31, 2020
Income Tax Examination [Line Items]
Tax credit carryforward		$ 7	$ 8
State NOL carryforward		$ 2	$ 2
Federal statutory rate		21.00%	21.00%	[1]	21.00%	[1]
State income tax on pretax income, net of federal tax effect		6.20%	6.20%	[1]	6.20%	[1]
Plant regulatory differences (a)	[2]	(3.80%)	(4.10%)	[1]	(19.30%)	[1]
Other tax credits, net NOL & tax credit allowances		(0.80%)	(1.00%)	[1]	(1.50%)	[1]
Amortization of excess nonplant deferred taxes		0.00%	0.00%	[1]	(12.60%)	[1]
Other, net		(0.70%)	(0.40%)	[1]	(0.80%)	[1]
Effective income tax rate		21.90%	21.70%	[1]	(7.00%)	[1]
Total income tax expense (benefit)		$ 35	$ 30		$ (7)
Deferred tax expense excluding items below		8	18		9
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities		(10)	(10)		(45)
Other		0	1		0
Deferred tax (benefit) expense		(2)	(9)		(36)
Environmental remediation		4	5
income tax expense [Member]
Income Tax Examination [Line Items]
Current federal tax expense		28	17		25
Current state tax expense		9	4		6
Current change in unrecognized tax benefit		0	0		(1)
Deferred federal tax (benefit) expense		(5)	3		(37)
Deferred state tax expense		3	6		1
Deferred ITCs		0	0		(1)
Total income tax expense (benefit)		35	30		$ (7)
Net Deferred Tax Liablility [Member]
Income Tax Examination [Line Items]
Tax credit carryforward		7	8
Deferred ITCs		(2)	(2)
Other		4	4
Deferred tax (benefit) expense		(59)	(61)
Difference between book and tax bases of property		343	331
Regulatory assets		25	29
Pension expense		10	11
Deferred fuel costs		6	8
Other		8	7
Total deferred tax liabilities		392	386
Regulatory liabilities		36	38
Other employee benefits		3	4
Rate refund		3	0
Net deferred tax liability		$ 333	$ 325

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

[2] 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.