Financial Instruments (Unaudited) Not Designated as Hedging Instruments (Details)	Sep. 30, 2011 lb
Fair Value Hedging [Member] \| FMC's copper futures and swap contracts [Member] \| Derivatives designated as hedging instruments [Member]
Derivative [Line Items]
Derivative held (in lbs except gold in oz)	73,000,000
Average contract price	3.90
Maturities through	December 2012
Atlantic Copper's copper forward commodity contracts [Member] \| Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Derivative held (in lbs except gold in oz)	3,000,000
Average contract price	3.38
Maturities through	October 2011
Embedded derivatives in provisional sales contracts - Copper [Member] \| Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Derivative held (in lbs except gold in oz)	598,000,000
Average contract price	4.08
Average market price	3.18
Maturities through	February 2012
Embedded derivatives in provisional sales contracts - Gold [Member] \| Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Derivative held (in lbs except gold in oz)	216,000
Average contract price	1,802
Average market price	1,626
Maturities through	January 2012
Embedded derivatives in provisional purchase contracts - Copper [Member] \| Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Derivative held (in lbs except gold in oz)	193,000,000
Average contract price	4.11
Average market price	3.18
Maturities through	January 2012

The average market price for a group of price risk forward or futures contracts, such as gas futures contracts.

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- Definition

The month of the latest date the derivative matures.

+ Details

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- Definition

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

+ Details

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- Definition

The average forward price on the group of price risk forward or futures contracts, such as gas futures contracts.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

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