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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