FINANCIAL INSTRUMENTS (Derivative) (Details)	Dec. 31, 2011 Derivatives designated as hedging instruments [Member] FMC's copper futures and swap contracts [Member] lb	Dec. 31, 2011 Derivatives not designated as hedging instruments [Member] Embedded derivatives in provisional sales contracts - Copper [Member] lb	Dec. 31, 2011 Derivatives not designated as hedging instruments [Member] Embedded derivatives in provisional sales contracts - Gold [Member] oz	Dec. 31, 2011 Derivatives not designated as hedging instruments [Member] Embedded derivatives in provisional purchase contracts - Copper [Member] lb	Dec. 31, 2011 Derivatives not designated as hedging instruments [Member] Embedded derivatives in provisional purchase contracts - Molybdenum [Member] lb	Dec. 31, 2011 Derivatives not designated as hedging instruments [Member] Atlantic Copper Copper Forward Commodity Contracts [Member] lb	Mar. 31, 2009 Derivatives not designated as hedging instruments [Member] PT Freeport Indonesia's copper forward contracts [Member] lb
Derivative [Line Items]
Derivative held (in lbs except gold in oz)	73,000,000	388,000,000	52,000	376,000,000	33,000	18,000,000	355,000,000
Average contract price	3.58	3.55	1,676	3.56	11.80	3.35	1.86
Average market price		3.44	1,576	3.45	11.78
Maturities	April 2013	June 2012	February 2012	April 2012	January 2012	March 2012