Commitments and Contingent Liabilities, Guarantees and Indemnifications (Details) (USD $)	Dec. 31, 2011
Guarantees [Abstract]
Assets held as collateral	$ 0
Guarantee amount	67,500,000
Current exposure	18,000,000
Payment or Performance Guarantee [Member] | Young Gas Storage Company Ltd. [Member]
Guarantees [Abstract]
Guarantor	Xcel Energy Inc.
Guarantee amount	500,000	[1]
Current exposure	0	[2]
Payment or Performance Guarantee [Member] | Obligations Under Stock Purchase Agreement [Member] | Xcel Energy Wholesale Group Inc. [Member]
Guarantees [Abstract]
Guarantor	Xcel Energy Inc.
Guarantee amount	17,500,000	[3]
Current exposure	17,500,000	[4]
Payment or Performance Guarantee [Member] | Obligations Under Stock Purchase Agreement [Member] | Xcel Energy Argentina Inc. [Member]
Guarantees [Abstract]
Guarantor	Xcel Energy Inc.
Guarantee amount	14,700,000	[5]
Current exposure	0	[4]
Claims made under guarantee	0
Payment or Performance Guarantee [Member] | Obligations Under Asset Purchase Agreements [Member] | Various Xcel Energy Inc. Subsidiaries [Member]
Guarantees [Abstract]
Guarantor	Xcel Energy Inc.
Guarantee amount	25,500,000	[5]
Current exposure	0	[4]
Claims made under guarantee	0
Payment or Performance Guarantee [Member] | Customer Loans for Farm Rewiring Program [Member]
Guarantees [Abstract]
Guarantor	NSP-Wisconsin
Guarantee amount	1,000,000	[1]
Current exposure	500,000	[6]
Payment or Performance Guarantee [Member] | Obligations Under Aircraft Leases [Member] | Xcel Energy Services Inc. [Member]
Guarantees [Abstract]
Guarantor	Xcel Energy Inc.
Guarantee amount	8,300,000	[7]
Current exposure	0	[2]
Payment or Performance Guarantee [Member] | Surety Bonds [Member]
Guarantees [Abstract]
Guarantor	Xcel Energy Inc.
Guarantee amount	31,200,000	[8],[9]
Current exposure		[10],[11]
Indemnification Agreement [Member] | Surety Bonds [Member] | Utility Engineering Corporation [Member]
Guarantees [Abstract]
Guarantee amount	80,000,000
Indemnification Agreement [Member] | Obligations Under Purchase and Sale Agreement of Lubbock Electric Distribution Assets [Member]
Guarantees [Abstract]
Guarantee amount	87,000,000
Current exposure	0
Indemnification Agreement [Member] | Obligations Under Acquisition of Nobles Wind Project [Member]
Guarantees [Abstract]
Guarantee amount	20,000,000
Current exposure	0
Generating capacity (in MW)	201
Indemnification Agreement [Member] | Obligations Under Acquisition of Generation Assets [Member]
Guarantees [Abstract]
Current exposure	$ 0
Generating capacity (in MW)	900

[1] The term of this guarantee is continuing.

[2] Nonperformance and/or nonpayment.

[3] The indemnification provisions of the guarantee expired in 2010. As of Dec. 31, 2011, there is a pending indemnification claim causing the guarantee liability to remain outstanding until the final resolution.

[4] Losses caused by default in performance of covenants or breach of any warranty or representation in the purchase agreement.

[5] The term of this guarantee is continuing. Certain representations and warranties relating to due organization, transaction authorization and tax matters survive indefinitely. As of Dec. 31, 2011, no claims have been made.

[6] The debtor becomes the subject of bankruptcy or other insolvency proceedings.

[7] The term of this guarantee expires in 2012 when the associated leases expire. At the time of renewal of the aircraft leases, the related guarantees will also be renewed.

[8] Xcel Energy Inc. has on ongoing agreement to indemnify an insurance company in connection with surety bonds they may issue or have issued for UE up to $80 million. Xcel Energy Inc.'s indemnification will be triggered only in the event that UE has failed to meet its obligations to the surety company.

[9] The expiration date of the surety bonds is project based. Accordingly, the surety bonds expire in conjunction with the completion of the related projects.

[10] Due to the magnitude of projects associated with the surety bonds, the total current exposure of this indemnification cannot be determined. Xcel Energy Inc. believes the exposure to be significantly less than the total amount of the outstanding bonds.

[11] Failure of Xcel Energy Inc. or one of its subsidiaries to perform under the agreement that is the subject of the relevant bond. In addition, per the indemnity agreement between Xcel Energy Inc. and the various surety companies, the surety companies have the discretion to demand that collateral be posted.