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Employee Benefit Plans (Details Textual) (USD $) In Millions, unless otherwise specified | 12 Months Ended |  |  |
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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%us-gaap_MultiemployerPlansCollectiveBargainingArrangementPercentageOfEmployersContributions / us-gaap_MultiemployerPlanNameAxis = myrg_EighthDistrictElectricalPensionFundMember | 5.00%us-gaap_MultiemployerPlansCollectiveBargainingArrangementPercentageOfEmployersContributions / us-gaap_MultiemployerPlanNameAxis = myrg_EighthDistrictElectricalPensionFundMember | 5.00%us-gaap_MultiemployerPlansCollectiveBargainingArrangementPercentageOfEmployersContributions / us-gaap_MultiemployerPlanNameAxis = myrg_EighthDistrictElectricalPensionFundMember
IBEW Local 1249 Pension Plan [Member] |  |  |  |  |  |
Defined Contribution Plans [Line Items] |  |  |  |  |  |
Multiemployer Plans, Collective-Bargaining Arrangement, Percentage of Employer's Contributions |  | 5.00%us-gaap_MultiemployerPlansCollectiveBargainingArrangementPercentageOfEmployersContributions / us-gaap_MultiemployerPlanNameAxis = myrg_IbewLocal1249PensionPlanMember | 5.00%us-gaap_MultiemployerPlansCollectiveBargainingArrangementPercentageOfEmployersContributions / us-gaap_MultiemployerPlanNameAxis = myrg_IbewLocal1249PensionPlanMember |  |  |
Multiemployer Plans, Pension [Member] |  |  |  |  |  |
Defined Contribution Plans [Line Items] |  |  |  |  |  |
Number Of Locals Covered Under Multiemployer Defined Plans | 100 myrg_NumberOfLocalsCoveredUnderMultiemployerDefinedPlans / us-gaap_MultiemployerPlanTypeAxis = us-gaap_MultiemployerPlansPensionMember |  |  |  |  |
Multiemployer Plans, Pension [Member] | Maximum [Member] |  |  |  |  |  |
Defined Contribution Plans [Line Items] |  |  |  |  |  |
Multiemployer Plans Red Zone Funded Status Percentage | 65.00%myrg_MultiemployerPlansRedZoneFundedStatusPercentage / us-gaap_MultiemployerPlanTypeAxis = us-gaap_MultiemployerPlansPensionMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |  |
Multiemployer Plans Yellow Zone Funded Status Percentage | 80.00%myrg_MultiemployerPlansYellowZoneFundedStatusPercentage / us-gaap_MultiemployerPlanTypeAxis = us-gaap_MultiemployerPlansPensionMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |  |
Multiemployer Plans, Pension [Member] | Minimum [Member] |  |  |  |  |  |
Defined Contribution Plans [Line Items] |  |  |  |  |  |
Multiemployer Plans Green Zone Funded Status Percentage | 80.00%myrg_MultiemployerPlansGreenZoneFundedStatusPercentage / us-gaap_MultiemployerPlanTypeAxis = us-gaap_MultiemployerPlansPensionMember / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  |  |
Employee Benefit Plan [Member] |  |  |  |  |  |
Defined Contribution Plans [Line Items] |  |  |  |  |  |
Defined Contribution Plan, Cost Recognized | 0.6 us-gaap_DefinedContributionPlanCostRecognized / myrg_DefinedContributionPlansAxis = myrg_EmployeeBenefitPlanMember | $ 0.6 us-gaap_DefinedContributionPlanCostRecognized / myrg_DefinedContributionPlansAxis = myrg_EmployeeBenefitPlanMember | $ 0.6 us-gaap_DefinedContributionPlanCostRecognized / myrg_DefinedContributionPlansAxis = myrg_EmployeeBenefitPlanMember |  |  |
Profit Sharing and Thrift Employee Benefit Plan [Member] |  |  |  |  |  |
Defined Contribution Plans [Line Items] |  |  |  |  |  |
Defined Contribution Plan, Cost Recognized | 6.9 us-gaap_DefinedContributionPlanCostRecognized / myrg_DefinedContributionPlansAxis = myrg_ProfitSharingAndThriftEmployeeBenefitPlanMember | $ 4.9 us-gaap_DefinedContributionPlanCostRecognized / myrg_DefinedContributionPlansAxis = myrg_ProfitSharingAndThriftEmployeeBenefitPlanMember | $ 5.9 us-gaap_DefinedContributionPlanCostRecognized / myrg_DefinedContributionPlansAxis = myrg_ProfitSharingAndThriftEmployeeBenefitPlanMember |  |  |

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- Details
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Namespace Prefix: | myrg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents the percentage funded for green zone status. + References No definition available. + Details
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Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents the percentage funded for red zone status. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage funded for yellow zone status. + References No definition available. + Details
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Namespace Prefix: | myrg_
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Balance Type: | na
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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 + Details
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- 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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- Details
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- Details
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- Details
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- Details
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- Details
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