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Investment in ATC and ATC Holdco (Details-1) - USD ($) $ in Thousands | 1 Months Ended | 3 Months Ended | 6 Months Ended
--- | --- | --- | ---
Jul. 31, 2026 | Jun. 30, 2026 | Jun. 30, 2025 | Jun. 30, 2026 | Jun. 30, 2025
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity earnings from investment |  |  |  | $ 7,336 | $ 6,241
Dividends from investments |  |  |  | 5,545 | 6,008
Capital contributions to investments | $ 3,600 |  |  | 7,714 | 5,871
MGE Transco [Member] | ATC [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity earnings from investment |  | $ 3,776 | $ 3,066 | 7,298 | 6,056
Dividends from investments |  | 2,788 | 2,345 | 5,450 | 5,632
Capital contributions to investments |  | $ 2,156 | $ 2,679 | $ 6,616 | $ 5,171

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