Borrowings and Other Financing Instruments, Credit Facilities (Details) - USD ($)		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Amount outstanding at period end		$ 183,000,000	$ 846,000,000
Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	2,750,000,000
Drawn	[2]	212,000,000
Available		2,538,000,000
Direct advances on the credit facility outstanding		$ 0
Xcel Energy Inc. | Credit Facilities
Line of Credit Facility [Line Items]
Maturity Date		Oct. 31, 2019
Credit Facility	[1]	$ 1,000,000,000
Drawn	[2]	25,000,000
Available		975,000,000
PSCo | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	700,000,000
Drawn	[2]	4,000,000
Available		696,000,000
NSP-Minnesota | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	500,000,000
Drawn	[2]	91,000,000
Available		409,000,000
SPS | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	400,000,000
Drawn	[2]	87,000,000
Available		313,000,000
NSP-Wisconsin | Credit Facilities
Line of Credit Facility [Line Items]
Credit Facility	[1]	150,000,000
Drawn	[2]	5,000,000
Available		145,000,000
Letter of Credit
Line of Credit Facility [Line Items]
Amount outstanding at period end		$ 29,000,000	$ 29,000,000

[1] These credit facilities expire in October 2019.

[2] Includes outstanding commercial paper and letters of credit.