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Share-Based Compensation (Tables) - Performance Units [Member] | 12 Months Ended
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Dec. 31, 2019
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. Grants since January 1, 2018, under this plan are as follows:
| Grant Date |  | MGE Energy Units Granted |
| January 17, 2020 |  | 5,048 |
| January 18, 2019 |  | 5,175 |
| March 1, 2018 |  | 1,106 |
| January 19, 2018 |  | 4,704 |
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. Grants since January 1, 2016, under this plan are as follows:
| Grant Date |  | MGE Energy Units Granted |
| February 15, 2019 |  | 17,022 |
| February 16, 2018 |  | 17,830 |
| March 1, 2017 |  | 14,704 |
| February 19, 2016 |  | 19,055 |

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- Definition Tabular disclosure of share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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