Borrowings and Other Financing Instruments, Credit Facilities (Details) (USD $)	Jun. 30, 2013		Dec. 31, 2012
Credit Facilities [Abstract]
Credit facility	$ 2,450,000,000	[1]
Drawn	369,700,000	[2]
Available	2,080,300,000
Credit facility bank borrowings outstanding	0		0
Xcel Energy Inc.
Credit Facilities [Abstract]
Credit facility	800,000,000	[1]
Drawn	278,000,000	[2]
Available	522,000,000
PSCo
Credit Facilities [Abstract]
Credit facility	700,000,000	[1]
Drawn	4,600,000	[2]
Available	695,400,000
NSP-Minnesota
Credit Facilities [Abstract]
Credit facility	500,000,000	[1]
Drawn	36,100,000	[2]
Available	463,900,000
SPS
Credit Facilities [Abstract]
Credit facility	300,000,000	[1]
Drawn	49,000,000	[2]
Available	251,000,000
NSP-Wisconsin
Credit Facilities [Abstract]
Credit facility	150,000,000	[1]
Drawn	2,000,000	[2]
Available	$ 148,000,000

[1] These credit facilities expire in July 2017.

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