Revenue Recognition - Additional Information (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($)
Disaggregation of Revenue [Line Items]
Remaining performance obligations	$ 1,540
Minimum
Disaggregation of Revenue [Line Items]
Term of master service agreements	1 year
Short termination notice of master service agreements	30 days
Maximum
Disaggregation of Revenue [Line Items]
Term of master service agreements	3 years
Short termination notice of master service agreements	90 days

Term of master service agreements ("MSAs"), in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

+ Details

Name:	myrg_MasterServiceAgreementsTerm
Namespace Prefix:	myrg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Short termination notice of master service agreements ("MSAs"), in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact

+ References

No definition available.

+ Details

Name:	myrg_MasterServiceAgreementsTermOfShortTerminationNotice
Namespace Prefix:	myrg_
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

No definition available.

+ Details

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

- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

+ Details

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

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Balance Type:
Period Type: