Derivative and Hedging Instruments (Details-1)		12 Months Ended
		Dec. 31, 2020 USD ($) Dth MWh MW		Dec. 31, 2019 USD ($) Dth MWh MW	Dec. 31, 2018 USD ($)
Derivative Fair Values [Abstract]
Collateral posted against derivative positions		$ 0		$ 1,500,000
Other Current Assets [Member]
Derivative Fair Values [Abstract]
Derivative fair value, net		1,162,000		1,100,000	$ 377,000
Commodity Contracts and Financial Transimission Rights [Member]
Derivative Fair Values [Abstract]
Derivative fair value, net		$ 200,000		$ (1,400,000)
Commodity Derivative Contracts [Member]
Gross Notional Volume of Open Derivatives
Notional amount, energy measure (in MWh) | MWh		259,080		417,840
Notional amount, decatherm measure (in Dth) | Dth		6,030,000		6,605,000
Derivative Fair Values [Abstract]
Asset Derivatives, fair value, gross basis		$ 806,000		$ 230,000
Liability Derivatives, fair value, gross basis		632,000		1,738,000
Collateral posted against derivative positions		0		1,546,000
Commodity Derivative Contracts [Member] | Other Current Assets [Member]
Derivative Fair Values [Abstract]
Asset Derivatives, fair value, gross basis		617,000	[1]	100,000
Liability Derivatives, fair value, gross basis	[1]	593,000
Commodity Derivative Contracts [Member] | Other Deferred Charges [Member]
Derivative Fair Values [Abstract]
Asset Derivatives, fair value, gross basis	[1]	189,000
Liability Derivatives, fair value, gross basis	[1]	39,000
Commodity Derivative Contracts [Member] | Derivative Liability (Current) [Member]
Derivative Fair Values [Abstract]
Asset Derivatives, fair value, gross basis	[1],[2]			157,000
Liability Derivatives, fair value, gross basis	[1],[2]			1,521,000
Commodity Derivative Contracts [Member] | Derivative Liability (Long-term) [Member]
Derivative Fair Values [Abstract]
Asset Derivatives, fair value, gross basis	[1]			73,000
Liability Derivatives, fair value, gross basis	[1]			217,000
Commodity Derivative Contracts [Member] | Cash Flow Hedging [Member]
Derivative Fair Values [Abstract]
Collateral posted against derivative positions		$ 0		$ 1,500,000
Energy Related Commodity Contract [Member] | Cash Flow Hedging [Member]
Derivatives Fair Value [Line Items]
Maximum term of derivative hedging contract		4 years
Financial Transmission Rights [Member]
Gross Notional Volume of Open Derivatives
Notional amount, power measure (in MW) | MW		2,869		2,750
Derivative Fair Values [Abstract]
Asset Derivatives, fair value, gross basis				$ 73,000
Liability Derivatives, fair value, gross basis		$ 23,000
Collateral posted against derivative positions		0
Financial Transmission Rights [Member] | Other Current Assets [Member]
Derivative Fair Values [Abstract]
Asset Derivatives, fair value, gross basis				73,000
Liability Derivatives, fair value, gross basis				$ 0
Financial Transmission Rights [Member] | Other Current Liabilities [Member]
Derivative Fair Values [Abstract]
Asset Derivatives, fair value, gross basis		0
Liability Derivatives, fair value, gross basis		$ 23,000
PPA [Member]
Gross Notional Volume of Open Derivatives
Notional amount, power measure (in MW) | MW		850		1,450
Derivative Fair Values [Abstract]
Derivative fair value, net		$ 14,100,000		$ 25,400,000
Liability Derivatives, fair value, gross basis		14,140,000		25,440,000
Collateral posted against derivative positions		0		0
PPA [Member] | Derivative Liability (Current) [Member]
Derivative Fair Values [Abstract]
Liability Derivatives, fair value, gross basis		10,160,000		10,100,000
PPA [Member] | Derivative Liability (Long-term) [Member]
Derivative Fair Values [Abstract]
Liability Derivatives, fair value, gross basis		$ 3,980,000		$ 15,340,000

[1] As of December 31, 2019, collateral of $1.5 million was posted against and netted with derivative liability positions on the consolidated balance sheets. No collateral was posted against derivative positions as of December 31, 2020.

[2] As of December 31, 2019, MGE posted $0.1 million as other current assets on the consolidated balance sheets.