Borrowings and Other Financing Instruments, Credit Facilities (Details) - USD ($)		3 Months Ended
		Mar. 31, 2018	Dec. 31, 2017
Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	$ 3,250,000,000
Drawn	[2]	1,056,000,000
Available		2,194,000,000
Direct advances on the credit facility outstanding		0	$ 0
Xcel Energy Inc. | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	1,500,000,000
Drawn	[2]	898,000,000
Available		$ 602,000,000
Maturity Date		Jun. 30, 2021
Xcel Energy Inc. | 364-Day Term Loan [Member]
Line of Credit Facility [Line Items]
Credit Facility		$ 500,000,000
Term of letters of credit (in years)		364 days
PSCo | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	$ 700,000,000
Drawn	[2]	99,000,000
Available		$ 601,000,000
Maturity Date		Jun. 30, 2021
NSP-Minnesota | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	$ 500,000,000
Drawn	[2]	25,000,000
Available		$ 475,000,000
Maturity Date		Jun. 30, 2021
SPS | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	$ 400,000,000
Drawn	[2]	12,000,000
Available		$ 388,000,000
Maturity Date		Jun. 30, 2021
NSP-Wisconsin | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	$ 150,000,000
Drawn	[2]	22,000,000
Available		$ 128,000,000
Maturity Date		Jun. 30, 2021

[1] These credit facilities expire in June 2021, with the exception of Xcel Energy Inc.’s $500 million 364-day term loan agreement entered into in December 2017.

[2] Includes outstanding commercial paper, term loan borrowings and letters of credit.