Borrowings and Other Financing Instruments Amended Credit Agreements (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jun. 30, 2019
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,100
Xcel Energy Inc. | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,250	$ 1,000
Xcel Energy Inc. | Swingline Subfacility [Domain]
Line of Credit Facility [Line Items]
Face Amount	75
SPS | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 500	$ 400