Rate Matters Rate Matters (Details) (USD $)	1 Months Ended							9 Months Ended
	Oct. 31, 2014 Subsequent Event MPSC Proceeding - Electric Rate Case 2015 Michigan Public Service Commission (MPSC)	Oct. 31, 2014 Subsequent Event MPSC Proceeding - Electric Rate Case 2015, Electric Rates 2016 Michigan Public Service Commission (MPSC)	May 31, 2014 NSP-Wisconsin PSCW Proceeding - Wisconsin Electric Rate Case 2015	Jan. 31, 2014 NSP-Wisconsin FERC Proceeding, MISO ROE Complaint [Member]	Nov. 30, 2013 NSP-Wisconsin FERC Proceeding, MISO ROE Complaint [Member]	Jun. 30, 2014 NSP-Wisconsin FERC Proceeding, MISO ROE Complaint [Member] Federal Energy Regulatory Commission (FERC)	Oct. 31, 2014 NSP-Wisconsin Subsequent Event PSCW Proceeding - Wisconsin Electric Rate Case 2015 Public Service Commission of Wisconsin (PSCW)	Sep. 30, 2014 Minimum NSP-Wisconsin FERC Proceeding, MISO ROE Complaint [Member]	Sep. 30, 2014 Maximum NSP-Wisconsin FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Percentage	6.10%	1.90%	3.20%
Public Utilities, Requested Return on Equity, Percentage	10.30%		10.20%
Public Utilities, percentage of earnings above the authorized ROE that will be refunded to customers			100.00%
Public Utilities, amount requested by public utility related to production and transmission fixed charges			$ 28,100,000
Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties, related to production and transmission fixed charges							26,400,000
Public Utilities, amount requested by public utility related to fuel and purchased power			13,900,000
Public Utilities, Adjustment to requested rate increase (decrease) related to fuel and purchased power							11,100,000
Public Utilities, requested base revenue increase (decrease) excluding NSP-Minnesota depreciation reserve and Monticello EPU deferral adjustments			42,000,000
Public Utilities, Adjustment to base revenue increase (decrease) recommended by third parties excluding NSP-Minnesota depreciation reserve and Monticello EPU deferrals							37,500,000
Public Utilities, Adjustment to requested rate increase (decrease) related to the NSP-Minnesota transmission depreciation reserve			(16,200,000)
Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties related to the NSP-Minnesota transmission depreciation reserve							(16,200,000)
Public Utilities, Adjustment to requested rate increase (decrease) related to the Monticello EPU deferral			(5,200,000)
Public Utilities, Adjustment to requested rate increase (decrease) recommended by third parties related to Monticello EPU depreciation deferrals							(5,200,000)
Public Utilities, Requested Rate Increase (Decrease), Amount	900,000	289,000	20,600,000
Public Utilities, Requested Equity Capital Structure, Percentage	52.59%
Public Utilities, Requested Rate Base, Amount	35,200,000
Public Utilities, ROE applicable to transmission formula rates in the MISO region, upper bound					12.38%
Public Utilities, ROE applicable to transmission formula rates in the MISO region, lower bound				9.15%	9.15%
Public Utilities, maximum equity capital structure percentage allowed per the complaint					50.00%
Public Utilities, number of steps required for newly adopted ROE discounted cash flow methodology						2
Public Utilities, reduction of transmission revenue, net of expense due to the new ROE methodology, lower bound								5,000,000	7,000,000
Public Utilities, Rate increase (decrease) recommended by third parties							16,100,000
Public utilities, Adjustment to requested rate increase (decrease) recommended by third parties, percentage							2.50%
The rate increase (decrease) requested of a regulatory body through an agreement between a public utility and another party or parties							$ 16,100,000