REGULATORY ENVIRONMENT (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended
	Aug. 31, 2014 Public Service Commission of Wisconsin (PSCW) 2015 Rates	Apr. 30, 2014 Public Service Commission of Wisconsin (PSCW) 2015 Rates	Dec. 31, 2013 Public Service Commission of Wisconsin (PSCW) 2014 Rates	Dec. 31, 2012 Public Service Commission of Wisconsin (PSCW) 2013 Rates	Aug. 31, 2014 Public Service Commission of Wisconsin (PSCW) Retail electric rate case 2015 Rates	Apr. 30, 2014 Public Service Commission of Wisconsin (PSCW) Retail electric rate case 2015 Rates	Dec. 31, 2013 Public Service Commission of Wisconsin (PSCW) Retail electric rate case 2014 Rates	Dec. 31, 2012 Public Service Commission of Wisconsin (PSCW) Retail electric rate case 2013 Rates	Aug. 31, 2014 Public Service Commission of Wisconsin (PSCW) Retail natural gas rate case 2015 Rates	Apr. 30, 2014 Public Service Commission of Wisconsin (PSCW) Retail natural gas rate case 2015 Rates	Dec. 31, 2013 Public Service Commission of Wisconsin (PSCW) Retail natural gas rate case 2014 Rates	Dec. 31, 2012 Public Service Commission of Wisconsin (PSCW) Retail natural gas rate case 2013 Rates	Oct. 31, 2014 Subsequent event Public Service Commission of Wisconsin (PSCW) 2015 Rates	Oct. 31, 2014 Subsequent event Public Service Commission of Wisconsin (PSCW) Retail electric rate case 2015 Rates	Oct. 31, 2014 Subsequent event Public Service Commission of Wisconsin (PSCW) Retail natural gas rate case 2015 Rates	Oct. 31, 2014 Subsequent event Michigan Public Service Commission (MPSC) [Member] Retail electric rate case 2015 Rates
Regulatory Environment
Requested annual increase (decrease) in rates for customers						$ 76.8				$ (1.6)						$ 5.7
Requested return on common equity percent reflected in rates of customers		10.60%														10.60%
Requested percent of capital structure composed of common equity		50.51%														50.48%
Recommended rate increase (decrease) in rates for customers					28.7				(13.6)
Recommended rate of return on common equity	10.20%
Recommended percent of capital structure composed of common equity	50.27%
Revised requested annual increase (decrease) in rates for customers														48	8
Revised requested return on common equity percent													10.20%
Revised requested percent of capital structure composed of common equity													50.27%
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