Commitments and Contingencies (Details-4) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)
MGE [Member]
Other Commitments [Line Items]
Other commitments, due in 2017	$ 1,317
Other commitments, due in 2018	1,175
Other commitments, due in 2019	511
Other commitments, due in 2020	497
Other commitments, due in 2021	440
Other commitment, due thereafter	5,646
MGE Energy [Member] | Investments in Non Public Entities, Capital Infusions [Member]
Other Commitments [Line Items]
Other commitment, initial agreed upon commitment total	$ 11,400
MGE Energy [Member] | Venture Debt Fund [Member]
Other Commitments [Line Items]
Other commitment, contract term, expiring in 2016	3 years
Other commitment, initial agreed upon commitment total	$ 1,500
Other commitments, total as of balance sheet date	$ 400