Rate Matters (Details) (Public Service Commission of Wisconsin (PSCW), USD $) In Millions, unless otherwise specified	1 Months Ended
	Dec. 31, 2013	Oct. 31, 2013	May 31, 2013
Electric and Gas Rate Case 2014, Electric Rates
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		$ 34.3
Public Utilities, Requested Rate Increase (Decrease), Amount			40.0
Public Utilities, Requested Rate Increase (Decrease), Percentage			6.50%
Public utilities, Adjustment to requested rate increase (decrease) related to DOE settlement proceeds, amount			(4.5)
Public Utilities, Approved Rate Increase (Decrease), Amount	19.5
Public Utilities, Approved Rate Increase (Decrease), Percentage	3.10%
Public Utilities, Approved Return on Equity, Percentage	10.20%
Public Utilities, Approved Equity Capital Structure, Percentage	52.50%
Public Utilities, Authorized Deferrals	4.1
Electric and Gas Rate Case 2014, Gas Rates
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		0
Public Utilities, Requested Rate Increase (Decrease), Amount			4.7
Public Utilities, Requested Rate Increase (Decrease), Percentage			3.80%
Electric and Gas Rate Case 2014
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Return on Equity, Percentage		10.40%	10.40%
Public Utilities, Requested Equity Capital Structure, Percentage			52.50%
Forecasted Average Net Investment Rate Base, Electric Utility			895.3
Forecasted Average Net Investment Rate Base, Natural Gas Utility			$ 89.8