Name:	mgee_JointlyOwnedUtilityPlantConstructionWorkInProgressAllowanceForFundsUsedDuringConstruction
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The portion of jointly owned utility plant costs recorded to construction work in progress related to capital expenditures.

No definition available.

Name:	mgee_JointlyOwnedUtilityPlantConstructionWorkInProgressCapitalExpenditures
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The portion of jointly owned utility plant costs recorded to property plant and equipment related to allowance for funds used during construction.

No definition available.

Name:	mgee_JointlyOwnedUtilityPlantPropertyPlantAndEquipmentAllowanceForFundsUsedDuringConstruction
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The portion of jointly owned utility plant costs recorded to property plant and equipment related to capital expenditures.

No definition available.

Name:	mgee_JointlyOwnedUtilityPlantPropertyPlantAndEquipmentCapitalExpenditures
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. This amount does not include constrcution work in progress. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

Name:	mgee_PropertyPlantAndEquipmentNetBeforeConstructionInProgress
Namespace Prefix:	mgee_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Rate the company is entitled to earn a return on construction work in progress as approved in the current rate case for the year.

No definition available.

Name:	mgee_PublicUtilitiesRateOfReturnPercentage
Namespace Prefix:	mgee_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

No definition available.

Name:	us-gaap_ContractualObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

The proportionate share of interest (percent) in a jointly owned utility plant.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 360

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 10.C)

-URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 10

-Section C

Name:	us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 835

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 835

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430

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

Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction.