Borrowings and Other Financing Instruments, Credit Facilities (Details) (USD $)	Mar. 31, 2013		Dec. 31, 2012
Credit Facilities [Abstract]
Credit facility	$ 2,450,000,000	[1]
Drawn	440,200,000	[2]
Available	2,009,800,000
Credit facility bank borrowings outstanding	0		0
Xcel Energy Inc. [Member]
Credit Facilities [Abstract]
Credit facility	800,000,000	[1]
Drawn	343,000,000	[2]
Available	457,000,000
PSCo [Member]
Credit Facilities [Abstract]
Credit facility	700,000,000	[1]
Drawn	4,000,000	[2]
Available	696,000,000
NSP-Minnesota [Member]
Credit Facilities [Abstract]
Credit facility	500,000,000	[1]
Drawn	56,200,000	[2]
Available	443,800,000
SPS [Member]
Credit Facilities [Abstract]
Credit facility	300,000,000	[1]
Drawn	16,000,000	[2]
Available	284,000,000
NSP-Wisconsin [Member]
Credit Facilities [Abstract]
Credit facility	150,000,000	[1]
Drawn	21,000,000	[2]
Available	$ 129,000,000

[1] These credit facilities expire in July 2017.

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