Represent the minimum interest coverage ratio under the credit agreement.

No definition available.

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

- Definition

Represents the maximum leveraged debt ratio under the credit agreement.

+ References

No definition available.

+ Details

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

- Definition

Represents the fees for the letter of credit facility, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	myrg_LetterOfCreditFeesPercentage
Namespace Prefix:	myrg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of fronting fees paid on the outstanding amount of letters of credit.

+ References

No definition available.

+ Details

Name:	myrg_LetterOfCreditFrontingFees
Namespace Prefix:	myrg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	myrg_LineOfCreditFacilityOptionToIncreaseMaximumBorrowingCapacity
Namespace Prefix:	myrg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentLineItems
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

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

+ References

No definition available.

+ Details

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

- Definition

The effective interest rate at the end of the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-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=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
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

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=myrg_SyndicatedCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt and Borrowing Arrangements (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended	1 Months Ended
	Dec. 31, 2014	Dec. 21, 2011	Dec. 31, 2013
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	19.3		$ 18.4
Borrowings Available Under The Credit Agreement	155.7
Maximum [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Variable rate basis	LIBOR
Maximum [Member] \| London Interbank Offered Rate [Member]
Debt Instrument [Line Items]
Interest rate margin (as a percent)	2.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Facing fees (as a percent)	0.125%
Commitment fee on unused portion of facility (as a percent)	0.20%
Revolving Credit Facility [Member] \| ABR [Member]
Debt Instrument [Line Items]
Variable rate basis	ABR
Revolving Credit Facility [Member] \| Prime Rate [Member]
Debt Instrument [Line Items]
Variable rate basis	Prime Rate
Revolving Credit Facility [Member] \| Federal Funds Effective Rate [Member]
Debt Instrument [Line Items]
Interest rate margin (as a percent)	0.50%
Variable rate basis	Federal Funds Effective Rate
Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Interest rate margin (as a percent)	1.00%
Variable rate basis	LIBOR
Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Interest rate margin (as a percent)	1.00%
Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest rate margin (as a percent)	0.00%
Revolving Credit Facility [Member] \| Minimum [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Interest rate margin (as a percent)	1.00%
Swing line Loans [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity		25.0
Letter of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Letter of credit fee (as a percent)	2.00%
Letter of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Letter of credit fee (as a percent)	1.00%
Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	19.3
Interest rate (as a percent)	1.125%
Syndicated Credit Agreement [Member]
Debt Instrument [Line Items]
Option to increase borrowing capacity		75.0
Maximum borrowing capacity		$ 175.0
Term of the credit agreement		5 years
Syndicated Credit Agreement [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Leveraged debt ratio	3.0
Syndicated Credit Agreement [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Interest coverage ratio	3.0