Schedule II - Valuation and Qualifying Accounts (Details) - USD ($)		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Regulatory Assets		$ 157,252,000		$ 145,746,000
Valuation and Qualifying Accounts [Roll Forward]
Balance at beginning of period		3,258,269		3,153,662	$ 3,174,945
Charged to costs and expenses		5,164,943	[1]	1,614,943	1,065,970
Charged to other accounts		26,400		20,160	320,400
Net accounts written off	[2]	(1,373,047)		(1,530,496)	(1,407,653)
Balance at end of period		7,076,565		$ 3,258,269	$ 3,153,662
Deferred COVID Allowance For Credit Loss [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 3,800,000

[1] As of December 31, 2020, MGE had deferred $3.8 million of incremental COVID-19-related costs as a regulatory asset. See Footnote 8 of the Notes to Consolidated Financial Statements in this Report for further information.

[2] Net of recovery of amounts previously written off