Borrowings and Other Financing Instruments Bilateral Credit Agreement (Details) - USD ($) $ in Millions	Dec. 31, 2022		Dec. 31, 2021
Short-term Debt [Line Items]
Amount outstanding at period end	$ 813		$ 1,005
Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	3,550
Letter of Credit
Short-term Debt [Line Items]
Amount outstanding at period end	43		19
NSP Minnesota | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	700	[1]	$ 500
NSP Minnesota | Letter of Credit | Bilateral Credit Agreement [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	75
Amount outstanding at period end	$ 54

[1] These credit facilities mature in September 2027.