Financial Instruments (Unaudited) Not Designated as Hedging Instruments (Details)	Sep. 30, 2012 lb
Embedded derivatives in provisional sales contracts - Copper [Member] | Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Open positions (in lbs except gold in oz)	557,000,000
Average contract price	3.49
Average market price	3.72
Maturities through	March 2013
Embedded derivatives in provisional sales contracts - Gold [Member] | Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Open positions (in lbs except gold in oz)	67,000
Average contract price	1,698
Average market price	1,781
Maturities through	December 2012
Embedded derivatives in provisional purchase contracts - Copper [Member] | Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Open positions (in lbs except gold in oz)	326,000,000
Average contract price	3.50
Average market price	3.72
Maturities through	January 2013
Atlantic Copper [Member] | Copper forward contracts [Member] | Derivatives not designated as hedging instruments [Member]
Derivative [Line Items]
Open positions (in lbs except gold in oz)	31,000,000
Average contract price	3.71
Maturities through	December 2012
Commodity Contract [Member] | Fair Value Hedging [Member] | Derivatives designated as hedging instruments [Member]
Derivative [Line Items]
Open positions (in lbs except gold in oz)	53,000,000
Average contract price	3.59
Maturities through	December 2013