Business combination payment through cash or common stock.

No definition available.

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Namespace Prefix:	meg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482665/350-30-50-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479907/805-20-50-5

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479328/805-10-50-2

+ Details

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

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479405/805-10-25-23

+ Details

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

- Definition

Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 30
-Paragraph 8
-SubTopic 30
-Topic 805
-Publisher FASB
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 30
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-SubTopic 30
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479637/805-30-30-7

+ Details

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

- Definition

For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479581/805-30-50-1

+ Details

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

- Definition

This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479328/805-10-50-2

+ Details

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

- Definition

This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

+ Details

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

- Definition

Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482573/350-20-50-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 25
-Paragraph 16
-SubTopic 10
-Topic 805
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479405/805-10-25-16

+ Details

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

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479581/805-30-50-1

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-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-13

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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- Details

Name:	us-gaap_BusinessAcquisitionAxis=meg_EnvironmentalAllianceIncMember
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=meg_GreenpathEnergyLtdMember
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- Details

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- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TradeNamesMember
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- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_NoncompeteAgreementsMember
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- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_SoftwareDevelopmentMember
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=meg_MatrixMember
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=meg_VandrensningMember
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Data Type:	na
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=meg_TriadEnvironmentalConsultantsIncMember
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Data Type:	na
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=meg_AirkineticsIncorporationMember
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=meg_HucoConsultingIncMember
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- Details

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- Details

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- Details

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- Details

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Business Acquisitions - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Jul. 31, 2023	Jun. 30, 2023	May 31, 2023	Feb. 28, 2023	Nov. 30, 2022	Aug. 31, 2022	Jan. 31, 2022
Business Acquisition [Line Items]
Transaction costs related to business combinations	$ 1,499	$ 368	$ 4,970	$ 1,354
Common Stock			2,598
Business combination, paid in cash			68,640
Acquisitions measurement period adjustments			$ (200)
EnvStd
Business Acquisition [Line Items]
Percentage of interests acquired											100.00%
EAI
Business Acquisition [Line Items]
Percentage of interests acquired								100.00%
GreenPath
Business Acquisition [Line Items]
Percentage of interests acquired							100.00%
GreenPath \| Customer Relationships
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			12 years
GreenPath \| Trade Names
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			1 year
GreenPath \| Covenants Not to Compete
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			5 years
GreenPath \| Proprietary Software
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			5 years
Matrix
Business Acquisition [Line Items]
Percentage of interests acquired						100.00%
Business combination, paid in cash			$ 46,563
Acquisitions measurement period adjustments			$ (15,053)
Matrix \| Customer Relationships
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			12 years
Matrix \| Trade Names
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			2 years 6 months
Matrix \| Covenants Not to Compete
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			5 years
Vandrensning
Business Acquisition [Line Items]
Percentage of interests acquired					100.00%
TriAD
Business Acquisition [Line Items]
Percentage of interests acquired										100.00%
AirKinetics
Business Acquisition [Line Items]
Percentage of interests acquired		100.00%		100.00%
Huco
Business Acquisition [Line Items]
Percentage of interests acquired									100.00%
EnvStd and IAG \| 2026 Earn Out
Business Acquisition [Line Items]
Payment through cash or common stock			$ 1,100
Common Stock			4,500
Business combination, earn-out payment, maximum	7,100		7,100
Business combination, paid in cash			1,500
Frontier, EAI, GreenPath and Matrix
Business Acquisition [Line Items]
Revenue	29,200		40,800
Pre-tax income (loss)	$ 6,500		7,400
All Other 2023 Acquisitions
Business Acquisition [Line Items]
Common Stock			2,598
Business combination, paid in cash			$ 22,077
All Other 2023 Acquisitions \| Customer Relationships
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			7 years
All Other 2023 Acquisitions \| Trade Names
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			2 years
All Other 2023 Acquisitions \| Covenants Not to Compete
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets			5 years
EnvStd, IAG, TriAD, AirKinetics and Huco
Business Acquisition [Line Items]
Revenue		$ 5,600		$ 13,200
Pre-tax income (loss)		$ 1,000		$ 1,700