Joint Plant Ownership (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2023 USD ($) MW	Mar. 31, 2022 USD ($)	Apr. 04, 2023 USD ($)	Dec. 31, 2022 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net		$ 1,890,784			$ 1,865,352
MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net		1,890,812			$ 1,865,380
Red Barn Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[2],[3]	18,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[1],[2],[3]	$ 400
Red Barn Units [Member] | Subsequent Event [Member]
Jointly Owned Utility Plant Interests [Line Items]
Property, plant, and equipment, net				$ 16,400
Red Barn Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[2],[3]	10.00%
Red Barn Units [Member] | Wind | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[2],[3]	9.16
Badger Hollow II Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[4]	$ 76,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[1],[4],[5]	$ 52,100
Badger Hollow II Units [Member] | Public Service Commission of Wisconsin [Member]
Allowance for Funds Used During Construction
Authorized AFUDC rate - Signficiant projects (100%)		100.00%
Badger Hollow II Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[4]	33.00%
Badger Hollow II Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[4]	50
Paris Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[6]	$ 51,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[1],[6]	$ 24,000
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	[6]	10.00%
Paris Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[6]	20
Paris Units [Member] | Battery storage | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[6]	11
Darien Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1],[7]	$ 45,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[1],[7]	$ 1,100
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	[7]	10.00%
Darien Units [Member] | Solar | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[7]	25
Darien Units [Member] | Battery storage | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW	[7]	7.5
West Riverside Energy Center [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected renewable project costs	[1]	$ 25,000
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[1]	$ 24,800
West Riverside Energy Center [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest		3.40%
West Riverside Energy Center [Member] | Natural gas | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, plant capacity (in MW) | MW		25
Badger Hollow II, Paris, and Darien Units [Member]
Allowance for Funds Used During Construction
AFUDC		$ 1,400	$ 400

[1] Excluding AFUDC.

[2] In April 2023, the Red Barn Wind Farm was placed in-service. MGE acquired its share of the project upon in-service date. MGE's share of the total costs incurred for Red Barn was $16.4 million after the April closing.

[3] The Red Barn Wind Farm is located in the Towns of Wingville and Clifton in Grant County, Wisconsin.

[4] The Badger Hollow II solar farm is located in southwestern Wisconsin in Iowa County, near the villages of Montfort and Cobb.

[5] Includes an allocation of common facilities at Badger Hollow placed in service in November 2021.

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

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