Other Income Tax Matters (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Examination [Line Items]
Tax Credit Carryforward, Amount		$ 2	$ 3
State NOL carryforward		$ 1	$ 2
Federal statutory rate		21.00%	21.00%	21.00%
State income tax on pretax income, net of federal tax effect		6.20%	6.20%	6.20%
Effective Income Tax Rate Reconciliation, Other Regulatory Items, Percent	[1]	(4.20%)	(3.40%)	(3.80%)
Other, net		0.00%	(1.10%)	(1.50%)
Effective income tax rate		23.00%	22.70%	21.90%
Total income tax expense		$ 40	$ 40	$ 35
Deferred tax expense (benefit) excluding items below		12	(3)	8
Amortization and adjustments to deferred income taxes on income tax regulatory assets and liabilities		(11)	(10)	(10)
Deferred tax benefit		0	(12)	(2)
Environmental remediation		4	4
Other		(1)	1	0
Credit Facilities
Income Tax Examination [Line Items]
Long-term Line of Credit		0	0
income tax expense [Member]
Income Tax Examination [Line Items]
Current federal tax expense		29	37	28
Current state tax expense		10	15	9
Deferred federal tax benefit		(3)	(10)	(5)
Deferred state tax expense (benefit)		3	(3)	3
Total income tax expense		40	40	35
Deferred Change In Unrecognized Tax Expense Benefit		0	1	0
Current Change In Unrecognized Tax Expense Benefit		1	0	$ 0
Net Deferred Tax Liablility [Member]
Income Tax Examination [Line Items]
Tax Credit Carryforward, Amount		2	3
Deferred tax benefit		(60)	(59)
Difference between book and tax bases of property		366	350
Regulatory assets		17	22
Pension expense		9	10
Other		10	7
Total deferred tax liabilities		402	389
Regulatory liabilities		40	32
Other employee benefits		4	4
Deferred Tax Assets Rate Refund		5	10
Deferred ITCs		2	2
Other		3	4
Net deferred tax liability		$ 342	$ 330

[1] 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.