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v3.26.1

Taxes (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2026 | Jun. 30, 2025 | Jun. 30, 2026 | Jun. 30, 2025
Effective Income Tax Rate Reconciliation, Percent [Abstract] |  |  |  |
Effective income tax rate | 11.40% | 10.10% | 11.00% | 12.00%
MGE [Member] |  |  |  |
Effective Income Tax Rate Reconciliation, Percent [Abstract] |  |  |  |
Effective income tax rate | 9.80% | 8.40% | 9.40% | 10.50%
Indemnification Agreement [Member] | Renewable Tax Credits Transferred [Member] |  |  |  |
Effects of The Inflation Reduction Act [Abstract] |  |  |  |
Guarantor Obligations, Liquidation Proceeds, Monetary Amount |  |  | $ 9.5 |

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