FINANCIAL INSTRUMENTS (Unrealized gains losses) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
FMC's copper futures and swap contracts [Member] | Amounts recorded in Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 0	[1]	$ 0	[1]	$ 64	[1]
Embedded derivatives in provisional sales contracts [Member] | Amounts recorded in Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(519)	[1]	619	[1]	1,393	[1]
Embedded derivatives in provisional purchase contracts - Copper [Member] | Amounts recorded in Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	0	[2]	(2)	[2]	(3)	[2]
PT Freeport Indonesia's copper forward contracts [Member] | Amounts recorded in Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	0	[1]	0	[1]	(104)	[1]
Atlantic Copper Copper Forward Commodity Contracts [Member] | Amounts recorded in Cost of Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	(2)	[2]	(30)	[2]	2	[2]
Fair Value Hedging [Member] | FMC's copper futures and swap contracts [Member] | Amounts recorded in Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative financial instruments	(28)		7		11
Hedged item	28		(7)		(11)
Realized gains (losses) from matured derivative financial instruments that qualified for hedge accounting	$ (28)		$ 37		$ 49

[1] Amounts recorded in revenues.

[2] Amounts recorded in cost of sales as production and delivery costs.