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OTHER LIABILITIES, INCLUDING EMPLOYEE BENEFITS (Target Asset Allocation) (Details)
 12 Months Ended
Dec. 31, 2014
Alternative Investments [Member]  
Target asset allocation [Line Items]  
Defined benefit plan, target allocation percentage of assets 10.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ invest_InvestmentAxis
= fcx_AlternativeInvestmentsMember
Equity Investments [Member]  
Target asset allocation [Line Items]  
Defined benefit plan, target allocation percentage of assets 45.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ invest_InvestmentAxis
= us-gaap_EquitySecuritiesMember
Fixed Income Investments [Member]  
Target asset allocation [Line Items]  
Defined benefit plan, target allocation percentage of assets 45.00%us-gaap_DefinedBenefitPlanTargetPlanAssetAllocations
/ invest_InvestmentAxis
= us-gaap_FixedIncomeInvestmentsMember