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v3.19.3.a.u2

Property, Plant, and Equipment (Tables) | 12 Months Ended
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Dec. 31, 2019
Property, Plant and Equipment [Abstract] |
Schedule of Property, Plant, and Equipment | Property, plant, and equipment consisted of the following as of December 31:
|  |  | MGE Energy |  |  | MGE |
| (In thousands) |  | 2019 |  | 2018 |  |  | 2019 |  | 2018 |
| Utility: |  |  |  |  |  |  |  |  |  |
| Electric(a)(b) | $ | 1,480,684 | $ | 1,310,421 |  | $ | 1,480,701 | $ | 1,310,438 |
| Gas |  | 472,123 |  | 442,581 |  |  | 472,134 |  | 442,593 |
| Total utility plant |  | 1,952,807 |  | 1,753,002 |  |  | 1,952,835 |  | 1,753,031 |
| Less: Accumulated depreciation and amortization(b) |  | 674,251 |  | 639,486 |  |  | 674,251 |  | 639,486 |
| In-service utility plant, net |  | 1,278,556 |  | 1,113,516 |  |  | 1,278,584 |  | 1,113,545 |
| Nonregulated: |  |  |  |  |  |  |  |  |  |
| Nonregulated |  | 323,266 |  | 322,855 |  |  | 323,266 |  | 322,855 |
| Less: Accumulated depreciation and amortization |  | 71,623 |  | 66,605 |  |  | 71,623 |  | 66,605 |
| In-service nonregulated plant, net |  | 251,643 |  | 256,250 |  |  | 251,643 |  | 256,250 |
| Construction work in progress: |  |  |  |  |  |  |  |  |  |
| Utility construction work in progress(a)(b)(c) |  | 111,707 |  | 138,663 |  |  | 111,707 |  | 138,663 |
| Nonregulated construction work in progress |  | 777 |  | 1,008 |  |  | 777 |  | 1,008 |
| Total property, plant, and equipment | $ | 1,642,683 | $ | 1,509,437 |  | $ | 1,642,711 | $ | 1,509,466 |
(a)In December 2017, a one-time tax impact, as a result of the Tax Act, decreased income tax provision and transmission investment $21.7 million and $20.4 million, respectively. (b)Includes long-term debt due within one year, debt issuance costs, and unamortized discount.

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- Definition Tabular disclosure of physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, balances by class of assets, depreciation and depletion expense and method used, including composite depreciation, and accumulated deprecation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(13)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
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