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

No definition available.

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

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in the five fiscal years thereafter (the aggregate net amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

No definition available.

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

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 1 after the balance sheet date.

No definition available.

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

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 5 after the balance sheet date.

No definition available.

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

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 4 after the balance sheet date.

No definition available.

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

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 3 after the balance sheet date.

No definition available.

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

The amount of the benefits expected to be paid, net of the prescription drug subsidy receipts expected to be received in Year 2 after the balance sheet date.

No definition available.

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

No definition available.

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

No definition available.

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

Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.

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

Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.

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

Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.

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

Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.

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

Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.

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

Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.

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

Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

Name:	us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

No definition available.

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

Amount of cash outflow for pension and other postretirement benefits. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585

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

Amount of prescription drug subsidy receipts expected after fifth fiscal year following latest fiscal year.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsAfterYearFive
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of prescription drug subsidy receipts expected in next fiscal year following latest fiscal year.

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of prescription drug subsidy receipts expected in fifth fiscal year following latest fiscal year.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsYearFive1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of prescription drug subsidy receipts expected in fourth fiscal year following latest fiscal year.

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsYearFour1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of prescription drug subsidy receipts expected in third fiscal year following latest fiscal year.

Name:	us-gaap_PrescriptionDrugSubsidyReceiptsYearThree1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of prescription drug subsidy receipts expected in second fiscal year following latest fiscal year.