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Represents the percentage funded for green zone status.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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- Definition

Represents the percentage funded for red zone status.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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- Definition

Represents the percentage funded for yellow zone status.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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- Definition

Represents information pertaining to number of locals covered under multiemployer defined plan.

+ References

No definition available.

+ Details

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

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Period Type:	duration

- Definition

Percentage of contributions required by a collective bargaining arrangement to all contributions required of an employer related to a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35742057&loc=SL14450657-114947

+ Details

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Data Type:	num:percentItemType
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- Details

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Namespace Prefix:
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- Details

Name:	myrg_DefinedContributionPlansAxis=myrg_ProfitSharingAndThriftEmployeeBenefitPlanMember
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- Details

Name:	us-gaap_MultiemployerPlanNameAxis=myrg_EighthDistrictElectricalPensionFundMember
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Data Type:	na
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- Details

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Employee Benefit Plans (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Eighth District Electrical Pension Fund [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plans, Collective-Bargaining Arrangement, Percentage of Employer's Contributions				5.00%	5.00%	5.00%
IBEW Local 1249 Pension Plan [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plans, Collective-Bargaining Arrangement, Percentage of Employer's Contributions		5.00%	5.00%
Multiemployer Plans, Pension [Member]
Defined Contribution Plans [Line Items]
Number Of Locals Covered Under Multiemployer Defined Plans	100
Multiemployer Plans, Pension [Member] \| Maximum [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plans Red Zone Funded Status Percentage	65.00%
Multiemployer Plans Yellow Zone Funded Status Percentage	80.00%
Multiemployer Plans, Pension [Member] \| Minimum [Member]
Defined Contribution Plans [Line Items]
Multiemployer Plans Green Zone Funded Status Percentage	80.00%
Employee Benefit Plan [Member]
Defined Contribution Plans [Line Items]
Defined Contribution Plan, Cost Recognized	0.6	$ 0.6	$ 0.6
Profit Sharing and Thrift Employee Benefit Plan [Member]
Defined Contribution Plans [Line Items]
Defined Contribution Plan, Cost Recognized	6.9	$ 4.9	$ 5.9