Joint Plant Ownership (Details) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2024 USD ($) MW	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) MW	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net		$ 2,073,061		$ 2,073,061		$ 2,018,121
MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net		2,073,089		2,073,089		$ 2,018,149
Paris Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[3]	61,000		61,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2],[3]	$ 40,200		$ 40,200
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%		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		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		11
Darien Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[4],[5]	$ 48,000		$ 48,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2],[5]	$ 37,600		$ 37,600
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%		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		25
Koshkonong Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[4],[6]	$ 65,000		$ 65,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2],[6]	$ 100		$ 100
Koshkonong Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)				100.00%
Koshkonong Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[6]	10.00%		10.00%
Koshkonong Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[6]	30		30
West Riverside Energy Center [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest		6.90%		6.90%
West Riverside Energy Center II [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[2]	$ 25,000		$ 25,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[2]	$ 25,200		$ 25,200
West Riverside Energy Center II [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest		3.50%		3.50%
West Riverside Energy Center II [Member] | Natural gas | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW		25		25
Darien, Paris, and Koshkonong Units [Member]
Allowance for Funds Used During Construction
AFUDC		$ 1,500	$ 600	$ 2,700	$ 1,000

[1] Estimated costs are expected to exceed PSCW previously approved Certificate of Authority (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.

[6] Koshkonong Solar Energy Center is located in the Towns of Christiana and Deerfield in Dane County, Wisconsin.