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Pension Plans and Postretirement Benefits - Weighted Average Assumptions used to Determine Net Periodic Benefit Obligations and Net Periodic Benefit Cost (Detail)
Dec. 31, 2014
Dec. 31, 2013
Domestic Plans [Member]    
Weighted average assumptions used to determine net periodic benefit obligations at December 31:    
Discount rate 4.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= mdr_DomesticDefinedBenefitPlanMember		 4.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= mdr_DomesticDefinedBenefitPlanMember
Rate of compensation increase 0.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= mdr_DomesticDefinedBenefitPlanMember		 0.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= mdr_DomesticDefinedBenefitPlanMember
TCN Plan [Member]    
Weighted average assumptions used to determine net periodic benefit obligations at December 31:    
Discount rate 3.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= mdr_ThirdCountryNationalEmployeesPensionPlanMember		 4.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= mdr_ThirdCountryNationalEmployeesPensionPlanMember
Rate of compensation increase 0.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= mdr_ThirdCountryNationalEmployeesPensionPlanMember		 0.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= mdr_ThirdCountryNationalEmployeesPensionPlanMember