Commitments and Contingencies, Guarantees and Indemnifications (Details) - USD ($)		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Xcel Energy Inc.
Guarantor Obligations [Line Items]
Assets held as collateral		$ 0	$ 0
Guarantees issued and outstanding		12,500,000
Current exposure under these guarantees		$ 100,000
Payment or Performance Guarantee | Customer Loans for Farm Rewiring Program | NSP-Wisconsin
Guarantor Obligations [Line Items]
Guarantor		NSP-Wisconsin
Guarantees issued and outstanding	[1],[2]	$ 1,000,000
Current exposure under these guarantees	[1],[2]	100,000
Claims made under guarantee		$ 0
Guarantee Expiration Date (year)		2020
Payment or Performance Guarantee | Obligations Under Aircraft Leases | Xcel Energy Inc.
Guarantor Obligations [Line Items]
Guarantor		Xcel Energy Inc.
Guarantees issued and outstanding	[3],[4]	$ 6,700,000
Current exposure under these guarantees	[3],[4]	$ 0
Guarantee Expiration Date (year)		2017
Payment or Performance Guarantee | Obligations Under Railcar Leases | NSP-Minnesota
Guarantor Obligations [Line Items]
Guarantor		NSP-Minnesota
Guarantees issued and outstanding	[5],[6]	$ 4,800,000
Current exposure under these guarantees	[5],[6]	$ 0
Guarantee Expiration Date (year)		2019
Payment or Performance Guarantee | Surety Bonds | Xcel Energy Inc.
Guarantor Obligations [Line Items]
Guarantor		Xcel Energy Inc.
Guarantees issued and outstanding	[7],[8],[9]	$ 41,300,000

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

[2] The term of this guarantee expires in 2020, which is the final scheduled repayment date for the loans. As of Dec. 31, 2015, no claims had been made by the lender.

[3] Nonperformance and/or nonpayment.

[4] The term of this guarantee expires in 2017 when the associated leases expire.

[5] Actual fair value of leased assets is less than the guaranteed residual value amount at the end of the lease term.

[6] The terms of this guarantee expires in 2019 when the associated lease expires.

[7] 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.

[8] Failure of any one of Xcel Energy Inc.’s utility 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.

[9] The surety bonds primarily relate to workers compensation benefits and utility projects. The workers compensation bonds are renewed annually and the project based bonds expire in conjunction with the completion of the related projects.