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v3.21.1

Debt - Schedule of Applicable Percentages (Detail) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020
Line Of Credit Facility [Line Items] |  |
Consolidated Leverage Ratio | 3.10% | 2.70%
Prior Senior Secured Credit Facility | Pricing Tier 1 |  |
Line Of Credit Facility [Line Items] |  |
Commitment Fee | 0.50% |
Prior Senior Secured Credit Facility | Pricing Tier 1 | Minimum |  |
Line Of Credit Facility [Line Items] |  |
Consolidated Leverage Ratio | 375.00% |
Prior Senior Secured Credit Facility | Pricing Tier 1 | Eurodollar Rate Loans and LIBOR Letter of Credit Fee |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 4.00% |
Prior Senior Secured Credit Facility | Pricing Tier 1 | Daily Floating Rate Loans |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 4.00% |
Prior Senior Secured Credit Facility | Pricing Tier 1 | Rate Loans |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 3.00% |
Prior Senior Secured Credit Facility | Pricing Tier 2 |  |
Line Of Credit Facility [Line Items] |  |
Commitment Fee | 0.50% |
Prior Senior Secured Credit Facility | Pricing Tier 2 | Maximum |  |
Line Of Credit Facility [Line Items] |  |
Consolidated Leverage Ratio | 375.00% |
Prior Senior Secured Credit Facility | Pricing Tier 2 | Minimum |  |
Line Of Credit Facility [Line Items] |  |
Consolidated Leverage Ratio | 300.00% |
Prior Senior Secured Credit Facility | Pricing Tier 2 | Eurodollar Rate Loans and LIBOR Letter of Credit Fee |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 3.50% |
Prior Senior Secured Credit Facility | Pricing Tier 2 | Daily Floating Rate Loans |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 3.50% |
Prior Senior Secured Credit Facility | Pricing Tier 2 | Rate Loans |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 2.50% |
Prior Senior Secured Credit Facility | Pricing Tier 3 |  |
Line Of Credit Facility [Line Items] |  |
Commitment Fee | 0.40% |
Prior Senior Secured Credit Facility | Pricing Tier 3 | Maximum |  |
Line Of Credit Facility [Line Items] |  |
Consolidated Leverage Ratio | 300.00% |
Prior Senior Secured Credit Facility | Pricing Tier 3 | Minimum |  |
Line Of Credit Facility [Line Items] |  |
Consolidated Leverage Ratio | 225.00% |
Prior Senior Secured Credit Facility | Pricing Tier 3 | Eurodollar Rate Loans and LIBOR Letter of Credit Fee |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 3.00% |
Prior Senior Secured Credit Facility | Pricing Tier 3 | Daily Floating Rate Loans |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 3.00% |
Prior Senior Secured Credit Facility | Pricing Tier 3 | Rate Loans |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 2.00% |
Prior Senior Secured Credit Facility | Pricing Tier 4 |  |
Line Of Credit Facility [Line Items] |  |
Commitment Fee | 0.30% |
Prior Senior Secured Credit Facility | Pricing Tier 4 | Maximum |  |
Line Of Credit Facility [Line Items] |  |
Consolidated Leverage Ratio | 225.00% |
Prior Senior Secured Credit Facility | Pricing Tier 4 | Eurodollar Rate Loans and LIBOR Letter of Credit Fee |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 2.50% |
Prior Senior Secured Credit Facility | Pricing Tier 4 | Daily Floating Rate Loans |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 2.50% |
Prior Senior Secured Credit Facility | Pricing Tier 4 | Rate Loans |  |
Line Of Credit Facility [Line Items] |  |
Interest rate | 1.50% |

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- Definition Consolidated leverage ratio. + References No definition available. + Details
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Namespace Prefix: | meg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
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- 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
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Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility. + References No definition available. + Details
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- Details
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