Rate Matters (Details) (USD $)	1 Months Ended						12 Months Ended	1 Months Ended
	May 31, 2014	Dec. 31, 2014	Oct. 31, 2014	Nov. 30, 2013	Nov. 30, 2014	Jun. 30, 2014	Dec. 31, 2014	Feb. 28, 2015
PSCW Proceeding - Wisconsin Electric Rate Case 2015 [Member] | Public Service Commission of Wisconsin (PSCW)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 20,600,000
Public Utilities, Requested Rate Increase (Decrease), Percentage	3.20%
NSP-Wisconsin [Member] | PSCW Proceeding - Wisconsin Electric Rate Case 2015 [Member] | Public Service Commission of Wisconsin (PSCW)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount		14,200,000
Public Utilities, Approved Rate Increase (Decrease), Percentage		2.20%
NSP-Wisconsin [Member] | MPSC Proceeding - Electric Rate Case 2015, Electric Rates 2016 [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			289,000
Public Utilities, Requested Rate Increase (Decrease), Percentage			1.90%
NSP-Wisconsin [Member] | MPSC Proceeding - Electric Rate Case 2015, Electric Rates 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			900,000
Public Utilities, Requested Rate Increase (Decrease), Percentage			6.10%
Public Utilities, Requested Return on Equity, Percentage			10.30%
Public Utilities, Requested Equity Capital Structure, Percentage			52.59%
Public Utilities, Requested Rate Base, Amount			35,200,000
NSP-Wisconsin [Member] | FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, maximum equity capital structure percentage allowed per the complaint				50.00%
NSP-Wisconsin [Member] | FERC Proceeding, MISO ROE Complaint [Member] | Federal Energy Regulatory Commission (FERC) [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, number of steps required for newly adopted ROE discounted cash flow methodology						2
Public Utilities, Incremental ROE basis point increase (decrease) recommended by third parties					50
Minimum | NSP-Wisconsin [Member] | FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, ROE applicable to transmission formula rates in the MISO region, lower bound, percentage				9.15%
Public Utilities, reduction of transmission revenue, net of expense due to the new ROE methodology							5,000,000
Maximum | NSP-Wisconsin [Member] | FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, ROE applicable to transmission formula rates in the MISO region, upper bound, percentage				12.38%
Public Utilities, reduction of transmission revenue, net of expense due to the new ROE methodology							$ 7,000,000
Subsequent Event | FERC Proceeding, MISO ROE Complaint [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Incremental ROE basis point increase (decrease) recommended by third parties								50
Public Utilities, ROE applicable to transmission formula rates in the MISO region, recommended by third parties								8.67%