Borrowings and Other Financing Instruments - Money Pool (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Short-term Debt [Line Items]
Short-term debt	$ 145	$ 75
Money Pool
Short-term Debt [Line Items]
Borrowing limit	100	100
Short-term debt	100	27
Average amount outstanding	41	46
Maximum amount outstanding	$ 100	$ 100
Weighted average interest rate, computed on a daily basis	5.33%	5.04%
Weighted average interest rate at period end	5.33%	5.34%
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	$ 500	$ 500
Short-term debt	145	75
Average amount outstanding	75	50
Maximum amount outstanding	$ 156	$ 119
Weighted average interest rate, computed on a daily basis	5.52%	5.12%
Weighted average interest rate at period end	5.52%	5.56%