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Investments (Details-2) - USD ($) $ in Thousands | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jan. 31, 2026 | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Schedule of Equity Method Investments [Line Items] |  |  |  |
Equity earnings of investments |  | $ 13,009 | $ 12,275 | $ 10,631
Dividends from investments |  | 10,987 | 8,834 | 8,508
Capital contributions to investments |  | 9,496 | 4,792 | 6,995
MGE Energy [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Equity earnings of investments |  | 136,204 | 121,310 | 120,394
MGE Transco [Member] | ATC [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Equity earnings of investments |  | 12,682 | 12,498 | 10,515
Dividends from investments |  | 10,612 | 8,635 | 8,397
Capital contributions to investments |  | $ 8,385 | $ 2,679 | 3,750
Ownership interest in equity-method investee |  | 3.60% | 3.60% |
MGE Transco [Member] | ATC [Member] | Subsequent Event [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Capital contributions to investments | $ 4,500 |  |  |
MGEE Transco [Member] | ATC Holdco [Member] |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Capital contributions to investments |  | $ 0 | $ 0 | $ 0
Ownership interest in equity-method investee |  | 4.40% | 4.40% |

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