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Uncompleted Contracts - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Jun. 30, 2014
Customer Contracts [Line Items]          
Contract Receivable Retainage, Due in Next Twelve Months $ 28.2us-gaap_ContractReceivableRetainageDueOneYearOrLess   $ 28.2us-gaap_ContractReceivableRetainageDueOneYearOrLess   $ 30.0us-gaap_ContractReceivableRetainageDueOneYearOrLess
Contract Receivable Retainage, Due after Next Twelve Months 2.5us-gaap_ContractReceivableRetainageDueAfterOneYear   2.5us-gaap_ContractReceivableRetainageDueAfterOneYear   4.3us-gaap_ContractReceivableRetainageDueAfterOneYear
Change In Accounting Estimate, Financial Effect, Operating Income $ 22.9mtrx_ChangeInAccountingEstimateFinancialEffectOperatingIncome $ 4.4mtrx_ChangeInAccountingEstimateFinancialEffectOperatingIncome $ 26.2mtrx_ChangeInAccountingEstimateFinancialEffectOperatingIncome $ 4.0mtrx_ChangeInAccountingEstimateFinancialEffectOperatingIncome  
Change in Accounting Estimate, Financial Effect, Net Income 7.9   9.0