Represent the minimum interest coverage ratio under the credit agreement.

No definition available.

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Namespace Prefix:	myrg_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold of debt coverage ration at which the credit agreement restricts certain types of payments.

+ References

No definition available.

+ Details

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Namespace Prefix:	myrg_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of debt instruments.

+ References

No definition available.

+ Details

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Namespace Prefix:	myrg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of company's consolidated liquidity restricted.

+ References

No definition available.

+ Details

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

- Definition

The Company has the option to expand the debt coverage ratio in the event of an acquisition.

+ References

No definition available.

+ Details

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

- Definition

Represents the option to increase maximum borrowings on the credit facility.

+ References

No definition available.

+ Details

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

- Definition

Percentage of capital stock from direct foreign subsidiaries pledged as collateral for a debt.

+ References

No definition available.

+ Details

Name:	myrg_PercentageOfCapitalStockFromDirectForeignSubsidiaries
Namespace Prefix:	myrg_
Data Type:	num: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

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section S45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68176171&loc=SL68176184-208336

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate during the reporting period.

+ 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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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

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

- 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

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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- Details

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Period Type:

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Name:	srt_RangeAxis=srt_MinimumMember
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Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
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Data Type:	na
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Data Type:	na
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Name:	srt_RangeAxis=srt_MaximumMember
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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
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- Details

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Debt - Additional Information (Details)		12 Months Ended
Debt - Additional Information (Details)	Sep. 13, 2019 USD ($)	Dec. 31, 2020 USD ($) equipment_note	Dec. 31, 2019 USD ($)
Credit Agreement \| Secured Debt
Debt Instrument [Line Items]
Debt instrument term	5 years
Maximum borrowing capacity	$ 375,000,000
Option to increase borrowing capacity	$ 200,000,000
Percentage of capital stock from direct foreign subsidiaries	65.00%
Debt instrument covenant leveraged debt ratio restriction	2.50
Debt instrument restricted maximum liquidity	$ 50,000,000
Interest rate on borrowings outstanding		2.35%
Leverage coverage ratio	3.0
Interest coverage ratio	3.0
Deferred debt issuance costs		$ 1,100,000
Credit Agreement \| Secured Debt \| Minimum
Debt Instrument [Line Items]
Commitment fee on unused capacity	0.15%
Credit Agreement \| Secured Debt \| Minimum \| Base Rate
Debt Instrument [Line Items]
Interest rate margin	0.00%
Credit Agreement \| Secured Debt \| Minimum \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margin	1.00%
Credit Agreement \| Secured Debt \| Maximum
Debt Instrument [Line Items]
Commitment fee on unused capacity	0.25%
Credit Agreement \| Secured Debt \| Maximum \| Base Rate
Debt Instrument [Line Items]
Interest rate margin	0.75%
Credit Agreement \| Secured Debt \| Maximum \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate margin	1.75%
Credit Agreement \| Secured Debt \| Letter of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 150,000,000
Letters of credit outstanding		10,400,000	$ 10,600,000
Credit Agreement \| Secured Debt \| Letter of Credit \| Insurance Program Obligations
Debt Instrument [Line Items]
Letters of credit outstanding		9,800,000	10,000,000.0
Credit Agreement \| Secured Debt \| Letter of Credit \| Contract Performance Obligations
Debt Instrument [Line Items]
Letters of credit outstanding		$ 600,000	$ 600,000
Credit Agreement \| Secured Debt \| Revolving Loans and Letters of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 75,000,000
Credit Agreement \| Secured Debt \| Non-performance Letters Of Credit \| Minimum
Debt Instrument [Line Items]
Letter of credit facility commitment percentage	1.00%
Credit Agreement \| Secured Debt \| Non-performance Letters Of Credit \| Maximum
Debt Instrument [Line Items]
Letter of credit facility commitment percentage	1.75%
Credit Agreement \| Secured Debt \| Performance letters of credit \| Minimum
Debt Instrument [Line Items]
Letter of credit facility commitment percentage	0.50%
Credit Agreement \| Secured Debt \| Performance letters of credit \| Maximum
Debt Instrument [Line Items]
Letter of credit facility commitment percentage	0.875%
Master Loan Agreement \| Notes Payable to Banks
Debt Instrument [Line Items]
Number of equipment notes \| equipment_note		4