- Definition

The amount of electric fuel rules monitored costs which have been deferred outside the symmetrical cost tolerance band authorized by a regulatory agency.

+ References

No definition available.

+ Details

Name:	mgee_Deferredfuelrulesmonitoredcosts
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	mgee_EffectsOfTheTaxCutsAndJobsActAbstract
Namespace Prefix:	mgee_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	mgee_FuelRulesAbstract
Namespace Prefix:	mgee_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Pursuant to the provisions of the rate order, the fuel rules bandwidth will be plus or minus this percentage.

+ References

No definition available.

+ Details

Name:	mgee_FuelRulesBandwidth
Namespace Prefix:	mgee_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Under fuel rules, the amount in which an entity is required to defer the benefit of lower costs if actual electric fuel costs were less than the allowed electric fuel costs in latest rate order.

+ References

No definition available.

+ Details

Name:	mgee_FuelRulesElectricFuelCostsDeferralLowerThreshold
Namespace Prefix:	mgee_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Under fuel rules, the amount in which an entity would defer if actual electric fuel costs exceeded allowed electric fuel costs in latest rate order.

+ References

No definition available.

+ Details

Name:	mgee_FuelRulesElectricFuelCostsDeferralUpperThreshold
Namespace Prefix:	mgee_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The fuel rules credit that is not required to be refunded to customers and will be amortized. The fuel credit will accrue interest at weighted cost of capital.

+ References

No definition available.

+ Details

Name:	mgee_PublicUtilitiesReturnOfFuelRulesCredit
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of income tax expense over-collection approved by the PSCW for a tax credit to be returned to customers via a bill credit.

+ References

No definition available.

+ Details

Name:	mgee_PublicUtilitiesReturnOfTaxCredit
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The 2021 rate settlement includes a one-time return to customers of the portion of electric excess deferred taxes related to the 2017 Tax Act not governed by IRS normalization rules.

+ References

No definition available.

+ Details

Name:	mgee_PublicUtilitiesReturnOfTaxCutsAndJobsActUnprotectedExcessDeferredTaxes
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's approved equity to capital, including debt and equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedEquityCapitalStructurePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedRateIncreaseDecreasePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRateMattersAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=mgee_TaxCutsAndJobsActMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=mgee_PublicServiceCommissionOfWisconsinMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=mgee_MgeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mgee_FuelRulesCreditYearAxis=mgee_Fuelrulesrefund2017memberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mgee_FuelRulesCreditYearAxis=mgee_FuelRulesRefund2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=mgee_ElectricRateProceedingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=mgee_GasRateProceedingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Rate Matters (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
Rate Matters (Details) - USD ($) $ in Millions	Oct. 31, 2019	Oct. 31, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fuel Rules [Abstract]
Deferred fuel rules monitored costs				$ 3.2	$ 1.5
Tax Cuts and Jobs Act [Member]
Effects Of The Tax Cuts And Jobs Act [Abstract]
Return of tax credit					$ 3.2	$ 8.2
PSCW [Member] \| MGE [Member]
Rate Proceedings [Abstract]
Approved equity capital structure, percentage				56.10%	56.60%
Authorized return on equity, percentage				9.80%	9.80%
Fuel Rules [Abstract]
Fuel rules, bandwidth				2.00%
Fuel rules, electric fuel costs, deferral, upper threshold				102.00%
Fuel rules, electric fuel costs, deferral, lower threshold				98.00%
PSCW [Member] \| Fuel Rules Refund, 2017 [Member] \| MGE [Member]
Fuel Rules [Abstract]
Return of electric fuel credit, total		$ 4.2
PSCW [Member] \| Fuel Rules Refund, 2018 [Member] \| MGE [Member]
Fuel Rules [Abstract]
Return of electric fuel credit, total	$ 9.5
PSCW [Member] \| Approved Future Rate Matters [Member] \| MGE [Member]
Rate Proceedings [Abstract]
Approved equity capital structure, percentage			55.80%
Authorized return on equity, percentage			9.80%
Fuel Rules [Abstract]
Fuel rules, bandwidth			1.00%
Electric Rate Proceeding [Member] \| PSCW [Member] \| MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage				(0.84%)	(2.24%)
Authorized rate increase (decrease), amount				$ (3.4)	$ (9.2)
Electric Rate Proceeding [Member] \| PSCW [Member] \| Approved Future Rate Matters [Member] \| MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage			0.00%
Effects Of The Tax Cuts And Jobs Act [Abstract]
Return of unprotected excess deferred taxes			$ 18.2
Gas Rate Proceeding [Member] \| PSCW [Member] \| MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage				1.46%	1.06%
Authorized rate increase (decrease), amount				$ 2.4	$ 1.7
Gas Rate Proceeding [Member] \| PSCW [Member] \| Approved Future Rate Matters [Member] \| MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage			4.00%