Borrowings and Other Financing Instruments - Money Pool (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Short-term Debt [Line Items]
Short-term debt	$ 0	$ 137
Money Pool
Short-term Debt [Line Items]
Borrowing limit	100	100
Short-term debt	0	91
Average amount outstanding	0	51
Maximum amount outstanding	$ 4	$ 100
Weighted average interest rate, computed on a daily basis	2.27%	0.05%
Weighted average interest rate at period end		0.05%
Commercial Paper
Short-term Debt [Line Items]
Borrowing limit	$ 500	$ 500
Short-term debt	0	137
Average amount outstanding	0	63
Maximum amount outstanding	$ 0	$ 342
Weighted average interest rate, computed on a daily basis		0.21%
Weighted average interest rate at period end		0.26%