REGULATORY ENVIRONMENT (Details) (Public Service Commission of Wisconsin (PSCW), USD $) In Millions, unless otherwise specified	1 Months Ended
	Apr. 30, 2014 2015 Rates	Dec. 31, 2013 2014 Rates	Dec. 31, 2012 2013 Rates	Apr. 30, 2014 Retail electric rate case 2015 Rates	Dec. 31, 2013 Retail electric rate case 2014 Rates	Dec. 31, 2012 Retail electric rate case 2013 Rates	Apr. 30, 2014 Retail natural gas rate case 2015 Rates	Dec. 31, 2013 Retail natural gas rate case 2014 Rates	Dec. 31, 2012 Retail natural gas rate case 2013 Rates
Regulatory Environment
Requested annual increase (decrease) in rates for customers				$ 76.8			$ (1.6)
Requested return on common equity percent reflected in rates of customers	10.60%
Requested percent of capital structure composed of common equity	50.51%
Approved annual increase (decrease) in rates for customers					(12.8)	28.5		4.0	(3.4)
Approved return on common equity percent reflected in rates of customers		10.20%	10.30%
Approved percent of capital structure composed of common equity		50.14%	51.61%
Fuel refund						20.5
Deferral related to pension and other employee benefits costs						7.3			2.1
Recovery of income tax amounts previously expensed related to the Federal Health Care Reform Act			5.9
Annual cap for decoupling						$ 14.0			$ 8.0