Commitments and Contingencies (Details-1) $ in Thousands	Jun. 30, 2017 USD ($)
Operating expense purchase contracts [Abstract]
Purchase obligation, 2017	$ 24,049
Purchase obligation, 2018	30,317
Purchase obligation, 2019	10,851
Purchase obligation, 2020	0
Purchase obligation, 2021	0
Purchase obligation, Thereafter	0
Coal [Member]
Operating expense purchase contracts [Abstract]
Purchase obligation, 2017	13,656	[1]
Purchase obligation, 2018	18,333	[1]
Purchase obligation, 2019	10,851	[1]
Purchase obligation, 2020	0	[1]
Purchase obligation, 2021	0	[1]
Purchase obligation, Thereafter	0	[1]
Natual Gas, Supply [Member]
Operating expense purchase contracts [Abstract]
Purchase obligation, 2017	10,393	[2]
Purchase obligation, 2018	11,984	[2]
Purchase obligation, 2019	0	[2]
Purchase obligation, 2020	0	[2]
Purchase obligation, 2021	0	[2]
Purchase obligation, Thereafter	0	[2]
MGE Energy [Member] | Investments in Non Public Entities, Capital Infusions [Member]
Other Commitments [Line Items]
Other commitment, initial agreed upon commitment total	$ 5,000

[1] Total coal commitments for the Columbia and Elm Road Units, including transportation. Fuel procurement for MGE's jointly owned Columbia and Elm Road Units is handled by WPL and WEPCO, respectively, who are the operators of those facilities.

[2] These commitments include market-based pricing.