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Financial statement tax effects of the Tax Cuts and Jobs Act.

No definition available.

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The amount of fuel savings approved by the PSCW for an electric fuel credit to be returned to customers via a bill credit.

No definition available.

Name:	mgee_Electricfuelcredit
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- References

No definition available.

Name:	mgee_FuelRulesAbstract
Namespace Prefix:	mgee_
Data Type:	xbrli:stringItemType
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Pursuant to the provisions of the rate order, the fuel rules bandwidth will be plus or minus this percentage.

No definition available.

Name:	mgee_FuelRulesBandwidth
Namespace Prefix:	mgee_
Data Type:	num:percentItemType
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Under fuel rules, the amount in which MGE 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.

No definition available.

Name:	mgee_FuelRulesElectricFuelDeferredCostsLowerThreshold
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Under fuel rules, the amount in which MGE would defer if actual electric fuel costs exceeded allowed electric fuel costs in latest rate order.

No definition available.

Name:	mgee_FuelRulesElectricFuelDeferredCostsUpperThreshold
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Data Type:	num:percentItemType
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The amount of excess deferred taxes related to the Tax Cuts and Jobs Act not governed by IRS normalization rules to be factored in rates.

No definition available.

Name:	mgee_PublicUtilitiesReturnOfTaxCutsAndJobsActUnprotectedExcessDeferredTaxes
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
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Percentage of public utility's approved equity to capital, including debt and equity.

No definition available.

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Data Type:	num:percentItemType
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Amount of public utility's approved rate increase (decrease) by regulatory agency.

No definition available.

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

No definition available.

Name:	us-gaap_PublicUtilitiesApprovedRateIncreaseDecreasePercentage
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Data Type:	num:percentItemType
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Percentage of public utility's approved return on equity.

No definition available.

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

- References

No definition available.

Name:	us-gaap_PublicUtilitiesRateMattersAbstract
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Percentage of public utility's requested rate increase (decrease) with regulatory agency.

No definition available.

Name:	us-gaap_PublicUtilitiesRequestedRateIncreaseDecreasePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Period Type:	duration

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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- References

No definition available.

Name:	us-gaap_RegulatoryAssetsAndLiabilitiesDisclosureAbstract
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Namespace Prefix:
Data Type:	na
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