Joint Plant Ownership (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2024 USD ($) MW	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net		$ 2,029,858		$ 2,018,121
MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net		2,029,886		$ 2,018,149
Paris Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[3]	61,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2],[3]	$ 35,700
Paris Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)		100.00%
Paris Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[3]	10.00%
Paris Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[3]	20
Paris Units [Member] | Battery storage | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[3]	11
Darien Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[4],[5]	$ 48,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2],[5]	$ 29,500
Darien Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)		100.00%
Darien Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[5]	10.00%
Darien Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[5]	25
Paris and Darien Units Member
Allowance for Funds Used During Construction
AFUDC		$ 1,200	$ 400

[1] Estimated costs are expected to exceed PSCW previously approved CA levels. Notifications are provided to the PSCW when costs increase above CA levels. MGE has and will continue to request recovery of the updates in its rate case proceedings.

[2] Excluding AFUDC.

[3] Paris Solar-Battery Park is located in the Town of Paris in Kenosha County, Wisconsin.

[4] As part of its order, the PSCW approved battery capacity with this project, which is no longer included in the current estimate. We will continue to evaluate timing, cost, and feasibility of the installation of batteries.

[5] Darien Solar Energy Center is located in Walworth and Rock Counties in southern Wisconsin.