Regulatory Assets and Liabilities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Regulatory Assets		$ 157,252,000	$ 145,746,000
Regulatory Liabilities [Line Items]
Regulatory Liabilities		183,903,000	174,193,000
MGE [Member] | PSCW [Member] | Electric Rate Proceeding [Member] | Scenario, Forecast [Member]
Regulatory Liabilities [Line Items]
Return of unprotected excess deferred taxes	$ 18,200,000
Deferred Fuel Savings [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5,047,000	1,794,000
Elm Road Regulatory Liability [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,957,000	2,322,000
Income Taxes [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		129,856,000	129,528,000
Non-ARO Removal Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		28,197,000	26,543,000
Pension and Other Postretirement Plans Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		7,524,000	4,499,000
Purchased Gas Adjustment [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,832,000	1,864,000
Renewable Energy Credits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		802,000	558,000
Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		7,669,000	6,019,000
Other Regulatory Liability [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,019,000	1,066,000
Asset Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11,935,000	10,756,000
COVID-19 Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3,933,000	0
Debt Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8,586,000	8,885,000
Deferred Pension And Other Postretirement Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5,280,000	6,216,000
Derivatives [Member]
Regulatory Assets [Line Items]
Regulatory Assets		13,989,000	26,875,000
Leases [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2,748,000	2,400,000
Tax Recovery AFUDC Equity [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8,952,000	7,060,000
Unfunded Pension and Other Postretirement Plans Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		101,594,000	83,214,000
Other Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 235,000	$ 340,000