Share-Based Compensation (Tables) - Performance Units [Member]

12 Months Ended

Dec. 31, 2017

Director Incentive Agreement [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Performance Unit Graded Vesting Schedule

Units granted under the Director Incentive Plan are subject to a three-year vesting schedule. The most recent three years of units granted under this plan are as follows:

Grant Date	MGE Energy Units Granted
January 19, 2018	4,704
January 20, 2017	4,608
January 15, 2016	3,773

Performance Unit Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Performance Unit Graded Vesting Schedule

Units granted under the Performance Unit Plan are subject to a five-year vesting schedule. The most recent units granted under this plan are as follows:

Grant Date	MGE Energy Units Granted
February 16, 2018	17,830
March 1, 2017	14,704
February 19, 2016	19,055
February 20, 2015	18,948
February 21, 2014	21,991