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Regional Transmission Organizations	12 Months Ended
Regional Transmission Organizations	Dec. 31, 2015
Regional Transmission Organizations Disclosure [Abstract]
Regional Transmission Organizations	Regional Transmission Organizations - MGE Energy and MGE. MGE reports on a net basis transactions on the MISO markets in which it buys and sells power within the same hour to meet electric energy delivery requirements. This treatment resulted in a $68.6 million, a $91.1 million, and a $78.0 million reduction to sales to the market and purchase power expense for MISO markets for the years ended December 31, 2015, 2014, and 2013, respectively.