Joint Plant Ownership (Details) $ in Millions		3 Months Ended
		Mar. 31, 2022 USD ($) MW	Mar. 31, 2021 USD ($)
Red Barn Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected Solar Farm Project Costs	[1],[2]	$ 18.0
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[1],[2]	$ 0.6
Red Barn Units [Member] | MGE [Member]
Jointly Owned Utility Plant Interests [Line Items]
Jointly owned utility plant, ownership interest	[2]	10.00%
Jointly owned utility plant, plant capacity (in MW) | MW	[2]	9.16
Badger Hollow II Units [Member]
Jointly Owned Utility Plant Interests [Line Items]
Projected Solar Farm Project Costs	[1],[3]	$ 65.0
Public Utilities, Property, Plant and Equipment, Construction Work in Progress	[1],[3],[4]	23.8
Allowance for Funds Used During Construction
AFUDC		$ 0.4	$ 0.1
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	[3]	33.00%
Jointly owned utility plant, plant capacity (in MW) | MW	[3]	50

[1] Excluding AFUDC.

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

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

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