Commitments and Contingencies (Details-1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 ppb MW
Columbia Environmental Project, SCR [Member] | MGE [Member]
Columbia Commitments
Share of projected project cost, minimum	30
Share of projected project cost, maximum	40
EPA [Member] | Legal Entity Type of Counterparty [Domain]
Effluent Limitations Guidelines and Standards for Steam Electric Power Generating Source Category [Abstract]
Proposed air pollution control and ash handling systems capacity at coal burning power plants, minimum (in MW)	50
EPA's Greenhouse Gas Reduction Guidelines
National average reduction of greenhouse gas emissions by the year 2030, percentage	30.00%
Wisconsin state average reduction goal of greenhouse gas emissions by the year 2030, percentage	34.00%
Compliance plan preparation term related to the greenhouse gas emissions reduction guidelines once the final rule is approved in 2015	2 years
Ozone NAAQS
Proposed lowered regulated level of Ozone NAAQS, minimum (in parts per billion)	65
Proposed lowered regulated level of Ozone NAAQS, maximum (in parts per billion)	70
Current regulated level of Ozone NAAQS (in parts per billion)	75
Proposed lowered regulated level of Ozone NAAQS, potential additional minimum (in parts per billion)	60
EPA's Coal Combustion Residuals Rule
Federal Register publication waiting period to become effective, term	6 months