Taxes	6 Months Ended
Jun. 30, 2017
Income Tax Disclosure [Abstract]
Taxes	Taxes - MGE Energy and MGE. MGE Energy's effective income tax rates for the three and six months ended June 30, 2017, were 36.0% and 36.4%, respectively, compared to 36.5% and 36.7% for the same periods in 2016. MGE's effective income tax rates for the three and six months ended June 30, 2017, were 35.5% and 35.9%, respectively, compared to 36.5% and 36.7% for the same periods in 2016. For both MGE Energy and MGE, the decrease in the effective tax rate is due in part to a higher estimated domestic manufacturing deduction in 2017. In addition, MGE's effective income tax rate decreased as a result of the transfer in December 2016 of its ownership interest in MGE Transco to MGE Energy.

Taxes

6 Months Ended

Jun. 30, 2017

Taxes - MGE Energy and MGE.

MGE Energy's effective income tax rates for the three and six months ended June 30, 2017, were 36.0% and 36.4%, respectively, compared to 36.5% and 36.7% for the same periods in 2016. MGE's effective income tax rates for the three and six months ended June 30, 2017, were 35.5% and 35.9%, respectively, compared to 36.5% and 36.7% for the same periods in 2016. For both MGE Energy and MGE, the decrease in the effective tax rate is due in part to a higher estimated domestic manufacturing deduction in 2017. In addition, MGE's effective income tax rate decreased as a result of the transfer in December 2016 of its ownership interest in MGE Transco to MGE Energy.