Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating expenses
Interest expense	$ 0	$ 0	$ 1
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	29	32
Accounts payable	63	66
NSP-Wisconsin
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	13	6
Accounts payable	0	0
PSCo
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	16	1
Accounts payable	0	0
SPS
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	0	0
Accounts payable	2	3
Other subsidiaries of Xcel Energy Inc.
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	0	25
Accounts payable	61	63
Purchased Power
Operating expenses
Costs and Expenses, Related Party	67	59	61
Transmission Expense
Operating expenses
Costs and Expenses, Related Party	121	109	116
Other Expense
Operating expenses
Costs and Expenses, Related Party	615	584	533
Electricity, US Regulated
Revenues [Abstract]
Operating Revenue from Related Parties	501	440	457
Natural Gas, US Regulated
Revenues [Abstract]
Operating Revenue from Related Parties	$ 1	$ 1	$ 1