Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Name:	us-gaap_IncomeLossFromEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Investment in ATC and ATC Holdco (Details-1) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2024	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Schedule of Equity Method Investments [Line Items]
Equity earnings from investment				$ 5,526	$ 5,240
Dividends from investments				4,238	4,248
Capital contributions to investments				3,159	3,376
MGE Transco [Member] \| ATC [Member]
Schedule of Equity Method Investments [Line Items]
Equity earnings from investment		$ 2,748	$ 2,599	5,470	5,182
Dividends from investments		2,132	2,042	4,238	4,248
Capital contributions to investments		$ 1,070	$ 1,601	$ 1,785	$ 1,958
MGE Transco [Member] \| ATC [Member] \| Subsequent Event [Member]
Schedule of Equity Method Investments [Line Items]
Capital contributions to investments	$ 900