Rate Matters Rate Matters (Details)				1 Months Ended							3 Months Ended	12 Months Ended
		Sep. 28, 2016	Jun. 30, 2016	Dec. 31, 2016 USD ($)	Oct. 31, 2016 USD ($)	Jul. 31, 2016 USD ($)	Apr. 30, 2016 USD ($)	Mar. 31, 2015 USD ($)	Feb. 28, 2015	Nov. 30, 2013	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) MW	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2008 USD ($)
Public Utilities, General Disclosures [Line Items]
Loss on Monticello life cycle management/extended power uprate project												$ 0	$ 5,237,000	$ 0
NSP-Wisconsin | PSCW Proceeding - Wisconsin 2017 Electric and Gas Rate Case - Electric Rates 2017
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount							$ 17,400,000
Public Utilities, Requested Rate Increase (Decrease), Percentage							2.40%
Public Utilities, Requested Rate Base, Amount							$ 1,188,000,000
Public utilities, Requested Increase Related To Rate Base Investments							11,000,000
Public Utilities, Requested Increase Related to Generation and Transmission Expenses	[1]						6,800,000
Public Utilities, Requested Increase Related to Fuel and Purchased Power Expenses							11,000,000
Public Utilities, Total Requested Rate Increase Excluding Refunds							28,800,000
Public Utilities, Requested Decrease Related to Fuel Refunds	[2]						(9,500,000)
Public Utilities, Requested Decrease Related to Settlement Refund							(1,900,000)
NSP-Wisconsin | PSCW Proceeding - Wisconsin 2017 Electric and Gas Rate Case - Gas Rates 2017
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount							$ 4,800,000
Public Utilities, Requested Rate Increase (Decrease), Percentage							3.90%
NSP-Wisconsin | PSCW Proceeding - Wisconsin 2017 Electric and Gas Rate Case
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Return on Equity, Percentage							10.00%
Percentage of Excess Earnings to be Refunded Due to Earnings Cap							100.00%
NSP-Wisconsin | MPSC Proceeding - Michigan 2017 Natural Gas Rate Case
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 347,000
Public Utilities, Requested Rate Increase (Decrease), Percentage					6.50%
Public Utilities, Requested Rate Base, Amount					$ 6,400,000
Public Utilities, Requested Return on Equity, Percentage					10.20%
Public Utilities, Requested Equity Capital Structure, Percentage					52.56%
Public Utilities, Requested Rider Revenue, Amount					$ 129,000
Public Utilities, Requested Rider Revenue, Percentage					2.40%
NSP-Wisconsin | Nuclear Project Prudency Investigation
Public Utilities, General Disclosures [Line Items]
Loss on Monticello life cycle management/extended power uprate project											$ 5,000,000
NSP-Wisconsin | Public Service Commission of Wisconsin (PSCW) | PSCW Proceeding - Wisconsin 2017 Electric and Gas Rate Case - Electric Rates 2017
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount				$ 22,500,000
Public Utilities, Approved Rate Increase (Decrease), Percentage				3.20%
Public Utilities, Approved Increase Related to Rate Base Investments				$ 7,600,000
Public Utilities, Approved Increase Related to Generation and Transmission Expenses	[1]			6,100,000
Public Utilities, Approved Increase Related to Fuel and Purchased Power Expenses				10,700,000
Public Utilities, Total Approved Rate Increase, Excluding Refunds				24,400,000
Public Utilities, Approved Decrease Related to Fuel Refunds	[2]			0
Public Utilities, Approved Decrease Related to Settlement Refund				(1,900,000)
Public Utilities, Revised Requested Rate Increase						$ 29,900,000
Public Utilities, Revised Requested Rate Increase, Percentage						4.20%
NSP-Wisconsin | Public Service Commission of Wisconsin (PSCW) | PSCW Proceeding - Wisconsin 2017 Electric and Gas Rate Case - Gas Rates 2017
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount				$ 4,800,000
Public Utilities, Approved Rate Increase (Decrease), Percentage				3.90%
NSP-Minnesota | Nuclear Project Prudency Investigation
Public Utilities, General Disclosures [Line Items]
Nuclear Project Expenditures, Amount															$ 665,000,000
Total Capitalized Nuclear Project Costs															$ 748,000,000
Initial Estimated Nuclear Project Expenditures																$ 320,000,000
Loss on Monticello life cycle management/extended power uprate project											129,000,000
NSP-Minnesota | FERC Proceeding, MISO ROE Complaint
Public Utilities, General Disclosures [Line Items]
Public Utilities, Base Return on Equity Charged to Customers Through Transmission Formula Rates									12.38%	12.38%
Public Utilities, ROE Applicable to Transmission Formula Rates in the MISO Region, Recommended by Third Parties									8.67%	9.15%
Public Utilities, Maximum Equity Capital Structure Percentage Allowed Per the Complaint										50.00%
NSP-Minnesota | Minnesota Public Utilities Commission | Nuclear Project Prudency Investigation
Public Utilities, General Disclosures [Line Items]
Public Utilities, Amount Of Recoverable Investment, With Return								$ 415,000,000
Public Utilities, Amount Of Recoverable Investment, Without A Return								$ 333,000,000
NSP-Minnesota | Federal Energy Regulatory Commission (FERC) | FERC Proceeding, MISO ROE Complaint
Public Utilities, General Disclosures [Line Items]
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, Approved		10.32%
Public Utilities, Length of Refund Period, In Months		15 months
Public Utilities, ROE Applicable To Transmission Formula Rates In The MISO Region, with RTO Adder, Approved												10.82%
Public Utilities, ROE Basis Point Adder, Approved												50
NSP-Minnesota | MPUC, NDPSC, SDPUC, and DOC | FERC Proceeding, MISO ROE Complaint
Public Utilities, General Disclosures [Line Items]
Public Utilities, ROE Applicable to Transmission Formula Rates in the MISO Region, Recommended by Third Parties												8.81%
NSP-Minnesota | FERC Staff | FERC Proceeding, MISO ROE Complaint
Public Utilities, General Disclosures [Line Items]
Public Utilities, ROE Applicable to Transmission Formula Rates in the MISO Region, Recommended by Third Parties												8.78%
NSP-Minnesota | MISO TOs | FERC Proceeding, MISO ROE Complaint
Public Utilities, General Disclosures [Line Items]
Public Utilities, ROE Applicable to Transmission Formula Rates in the MISO Region, Recommended by Third Parties												10.92%
NSP-Minnesota | Administrative Law Judge | FERC Proceeding, MISO ROE Complaint
Public Utilities, General Disclosures [Line Items]
Public Utilities, ROE Applicable to Transmission Formula Rates in the MISO Region, Recommended by Third Parties			9.70%
Xcel Energy Inc. | Nuclear Project Prudency Investigation
Public Utilities, General Disclosures [Line Items]
Loss on Monticello life cycle management/extended power uprate project											$ 129,000,000
Minimum | NSP-Minnesota | Nuclear Project Prudency Investigation
Public Utilities, General Disclosures [Line Items]
Public Utilities, Facility Generating Capacity, In MW | MW													600
Maximum | NSP-Minnesota | Nuclear Project Prudency Investigation
Public Utilities, General Disclosures [Line Items]
Public Utilities, Facility Generating Capacity, In MW | MW													671

[1] Includes Interchange Agreement billings. For financial reporting purposes, these expenses are included in O&M.

[2] In July 2016, the PSCW required NSP-Wisconsin to return the 2015 fuel refund directly to customers, rather than using it to offset the proposed 2017 rate increase, as originally proposed by NSP-Wisconsin. This decision, when combined with the increase in forecasted fuel and purchased power expense, effectively increased NSP-Wisconsin’s requested electric rate increase to $29.9 million, or 4.2 percent.