Commitments and Contingencies (Details-3) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) ppb pollutant state MW
Columbia Environmental Project, SCR [Member] | MGE [Member] | Minimum [Member]
Columbia
Share of projected SCR project cost | $	$ 22
Columbia Environmental Project, SCR [Member] | MGE [Member] | Maximum [Member]
Columbia
Share of projected SCR project cost | $	$ 24
Wisconsin Energy Efficiency and Renewables Act [Member]
Energy Efficiency and Renewables
Minimum electricity generated from renewable resources	10.00%
EPA [Member]
Effluent Limitations Guidelines and Standards for Steam Electric Power Generating Source Category [Abstract]
Air pollution control and ash handling systems capacity at coal burning power plants, minimum (in MW) | MW	50
EPA's National Ambient Air Quality Standards
Number of pollutants monitored by the National Ambient Air Quality Standards | pollutant	6
EPA's Ozone NAAQS
Current primary regulated level of Ozone NAAQS (in parts per billion) | ppb	70
Current secondary regulated level of Ozone NAAQS (in parts per billion) | ppb	70
EPA's Cross State Air Pollution Rule
Number of states incorporating 2008 ozone NAAQS attainment levels | state	22