Consolidated leverage ratio.

No definition available.

Name:	meg_ConsolidatedLeverageRatio
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum net leverage ratio.

+ References

No definition available.

+ Details

Name:	meg_MaximumNetLeverageRatio
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum net leverage ratio year three.

+ References

No definition available.

+ Details

Name:	meg_MaximumNetLeverageRatioYearThree
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum net leverage ratio year two.

+ References

No definition available.

+ Details

Name:	meg_MaximumNetLeverageRatioYearTwo
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Minimum fixed charge coverage ratio.

+ References

No definition available.

+ Details

Name:	meg_MinimumFixedChargeCoverageRatio
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of interest rate reduction.

+ References

No definition available.

+ Details

Name:	meg_PercentageOfInterestRateReduction
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of proceeds of certain dispositions, subject to customary reinvestment rights.

+ References

No definition available.

+ Details

Name:	meg_PercentageOfProceedsOfCertainDispositionsSubjectToCustomaryReinvestmentRights
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of proceeds of debt subject to customary exceptions.

+ References

No definition available.

+ Details

Name:	meg_PercentageOfProceedsOfDebtSubjectToCustomaryExceptions
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of proceeds of insurance or condemnation, subject to customary reinvestment rights.

+ References

No definition available.

+ Details

Name:	meg_PercentageOfProceedsOfInsuranceOrCondemnationSubjectToCustomaryReinvestmentRights
Namespace Prefix:	meg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=123599511&loc=d3e64711-112823

+ Details

Name:	us-gaap_DebtInstrumentPeriodicPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date the credit facility terminates, in YYYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Details

Name:	us-gaap_VariableRateAxis=meg_FloatingRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=meg_TwentyTwentyOneCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=meg_IncrementalTermLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=meg_EquipmentLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=meg_TermLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt - Additional Information (Details) - USD ($)				1 Months Ended		3 Months Ended		7 Months Ended	12 Months Ended
Debt - Additional Information (Details) - USD ($)	Jan. 27, 2022	Jan. 26, 2022	Apr. 27, 2021	Apr. 30, 2023	Jan. 31, 2023	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Dec. 31, 2022
Floating Component \| Interest Rate Swap
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000.0
Credit facility maturity date	Jan. 27, 2025
Interest rate	1.39%
2021 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 300,000,000.0
Credit facility maturity date			Apr. 27, 2026
Percentage of interest rate reduction								0.05%
Maximum net leverage ratio			425.00%
Maximum net leverage ratio year two			400.00%
Maximum net leverage ratio year three			375.00%
Minimum fixed charge coverage ratio			125.00%
Consolidated total leverage ratio						140.00%			130.00%
Percentage of proceeds of debt, subject to customary exceptions						100.00%
Percentage of proceeds of certain dispositions, subject to customary reinvestment rights						100.00%
Percentage of proceeds of insurance or condemnation, subject to customary reinvestment rights						100.00%
Weighted average interest rate						6.10%	1.80%	6.10%
Incremental Term Loans
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 150,000,000.0
Equipment Line Of Credit
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity									$ 10,000,000.0
Credit facility maturity date						Mar. 31, 2023
Term Loan Facility \| 2021 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			175,000,000.0
Installment repayment amount		$ 2,200,000		$ 2,200,000	$ 2,200,000		$ 2,200,000
Revolving Line of Credit \| 2021 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			125,000,000.0
Revolving Line of Credit \| Letter of Credit \| 2021 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 20,000,000.0