Short-Term Borrowings (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Amount outstanding at period end	$ 145	$ 145	$ 75
Money Pool
Short-term Debt [Line Items]
Borrowing limit	100	100	100	$ 100
Amount outstanding at period end	7	7	27	0
Average amount outstanding	6	24	46	35
Maximum amount outstanding	$ 60	$ 100	$ 100	$ 100
Weighted average interest rate, computed on a daily basis (percentage)	4.58%	5.29%	5.04%	0.44%
Line of Credit Facility, Interest Rate at Period End	4.58%	4.58%	5.34%
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	$ 500	$ 500	$ 500	$ 500
Amount outstanding at period end	145	145	75	34
Average amount outstanding	13	35	50	100
Maximum amount outstanding	$ 145	$ 160	$ 119	$ 324
Weighted average interest rate, computed on a daily basis (percentage)	4.70%	5.47%	5.12%	0.79%
Weighted average interest rate at period end (percentage)	4.66%	4.66%	5.56%	4.55%