Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	$ 13	$ 8
Accounts payable	69	58
NSP-Minnesota
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	0	0
Accounts payable	16	1
NSP-Wisconsin
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	0	0
Accounts payable	2	1
SPS
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	0	0
Accounts payable	7	6
Other subsidiaries of Xcel Energy Inc.
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	13	8
Accounts payable	44	50
Other Expense
Operating expenses
Costs and Expenses, Related Party	617	571	$ 532
Other Revenue
Operating revenues
Operating Revenue from Related Parties	$ 5	$ 5	$ 5