Borrowings and Other Financing Instruments - Commercial Paper (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Short-term debt	$ 78	$ 34
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	500	500
Short-term debt	78	34
Average amount outstanding	88	100
Maximum amount outstanding	$ 118	$ 324
Weighted average interest rate, computed on a daily basis	4.86%	0.79%
Weighted average interest rate at period end	5.58%	4.55%