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Retirement Plan Benefits - Weighted Average Target Asset Allocations (Details)
 12 Months Ended
Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]  
Weighted average target asset allocation 100.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
U.S. large capitalization equities  
Defined Benefit Plan Disclosure [Line Items]  
Weighted average target asset allocation 17.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= emc_USLargeCapitalizationEquitiesMember
U.S. small capitalization equities  
Defined Benefit Plan Disclosure [Line Items]  
Weighted average target asset allocation 4.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= emc_USSmallCapitalizationEquitiesMember
International equities  
Defined Benefit Plan Disclosure [Line Items]  
Weighted average target asset allocation 4.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= emc_InternationalEquitiesMember
U.S. long-duration fixed income  
Defined Benefit Plan Disclosure [Line Items]  
Weighted average target asset allocation 75.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis
= emc_USLongDurationFixedIncomeMember