Derivative and Hedging Instruments (Details-1) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2022 USD ($) Dth1 MWh MW	Dec. 31, 2021 USD ($) Dth1 MWh MW	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Derivative fair values [Abstract]
Collateral posted against derivative positions		$ 6,900	$ 1,300
Other Current Assets [Member]
Derivative fair values [Abstract]
Derivative, Fair Value, Net		267	770	$ 173	$ 1,162
Commodity Contracts And Financial Transimission Rights [Member]
Derivative fair values [Abstract]
Derivative, Fair Value, Net		$ 9,800	$ 2,800
Commodity Contract [Member]
Gross Notional Volume of Open Derivatives [Abstract]
Notional amount, energy measures (in MWh) | MWh		369,960	278,000
Notional amount, decatherm measure (in Dth) | Dth1		3,260,000	5,735,000
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset		$ 10,144	$ 3,379
Derivative Liability, Fair Value, Gross Liability		357	849
Collateral posted against derivative positions		6,911	1,254
Commodity Contract [Member] | Other Current Assets [Member]
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset	[1]	9,518	2,959
Derivative Liability, Fair Value, Gross Liability	[1]	325	811
Commodity Contract [Member] | Other Deferred Charges [Member]
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset	[1]	626	420
Derivative Liability, Fair Value, Gross Liability	[1]	32	38
Commodity Contract [Member] | Cash Flow Hedging [Member]
Derivative fair values [Abstract]
Collateral posted against derivative positions		$ 6,900	$ 1,300
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 [Abstract]
Notional amount, power measure (in MW) | MW		858	2,127
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset			$ 227
Derivative Liability, Fair Value, Gross Liability		$ 16
Collateral posted against derivative positions			0
Financial Transmission Rights [Member] | Other Current Assets [Member]
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset			227
Derivative Liability, Fair Value, Gross Liability			$ 0
Financial Transmission Rights [Member] | Derivative Liability (Current) [Member]
Derivative fair values [Abstract]
Derivative Asset, Fair Value, Gross Asset	[1]	0
Derivative Liability, Fair Value, Gross Liability	[1]	$ 16
PPA [Member]
Gross Notional Volume of Open Derivatives [Abstract]
Notional amount, power measure (in MW) | MW		100	250
Derivative fair values [Abstract]
Derivative, Fair Value, Net		$ (100)	$ (2,100)
Derivative Liability, Fair Value, Gross Liability		130	2,140
PPA [Member] | Derivative Liability (Current) [Member]
Derivative fair values [Abstract]
Derivative Liability, Fair Value, Gross Liability		$ 130	$ 2,140

[1] As of March 31, 2022 and December 31, 2021, MGE received collateral of $6.9 million and $1.3 million, respectively, from counterparties under a master netting agreement for outstanding exchange traded derivative positions. The fair value of the derivative asset disclosed in this table has not been reduced for the collateral received.