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Fair Value Accounting - Additional Information (Detail) (USD $)
Mar. 31, 2015
Level 2 [Member]  
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]  
Estimated fair value of outstanding debt $ 6,437us-gaap_DebtInstrumentFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Carrying value of debt $ 6,452us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Level 3 [Member]  
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]  
Assets measured at fair value hierarchy, percent 2.00%nem_AssetsMeasuredAtFairValueHierarchyInPercent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Liabilities measured at fair value hierarchy, percent 57.00%nem_LiabilitiesMeasuredAtFairValueHierarchyInPercent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member