REGULATORY ENVIRONMENT (Details) (Public Service Commission of Wisconsin (PSCW), USD $) In Millions, unless otherwise specified				0 Months Ended
	Mar. 29, 2013 2014 Rates Entity's original request	Mar. 29, 2013 2014 Rates Retail electric rate case Entity's original request	Mar. 29, 2013 2014 Rates Natural gas rate case Entity's original request	Dec. 06, 2012 2013 Rates Settlement agreement	Dec. 06, 2012 2013 Rates Retail electric rate case Settlement agreement	Dec. 06, 2012 2013 Rates Natural gas rate case Settlement agreement	Dec. 09, 2011 2012 Rates Retail electric rate case Rate order	Dec. 09, 2011 2012 Rates Natural gas rate case Rate order	Jul. 31, 2013 Subsequent Event [Member] 2014 Rates Regulatory authorities staff recommendations	Jul. 31, 2013 Subsequent Event [Member] 2014 Rates Retail electric rate case Regulatory authorities staff recommendations	Jul. 31, 2013 Subsequent Event [Member] 2014 Rates Natural gas rate case Regulatory authorities staff recommendations
Regulatory Proceedings:
Requested rate increase (decrease)		$ 71.1	$ 19.0
Recommended percent of capital structure composed of common equity									50.14%
Recommended rate increase (decrease)										9.3	7.8
Requested return on common equity percent	10.75%
Recommended return on common equity percent									10.20%
Requested percent of capital structure composed of common equity	51.11%
Authorized rate increase (decrease)					28.5	(3.4)	8.1	(7.2)
Deferred of pension and other employee benefit costs						2.1
Estimated fuel refund					20.5
Authorized return on common equity percent				10.30%
Authorized percent of capital structure composed of common equity				51.61%
Annual cap for decoupling					14.0	8.0
Authorized recovery of income tax amounts previously expensed related to the Federal Health Care Reform Act				$ 5.9
Percentage of price variance from the cost of fuel and purchased power included in rates							2.00%