Financial Instruments (Unaudited) Not Designated as Hedging Instruments (Details)	9 Months Ended
	Sep. 30, 2014 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)	554,000,000
Average contract price	3.14
Average market price	3.03
Maturities through	February 2015
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)	301,000
Average contract price	1,259
Average market price	1,214
Maturities through	January 2015
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)	98,000,000
Average contract price	3.16
Average market price	3.03
Maturities through	January 2015
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)	46,000,000
Average contract price	3.12
Maturities through	November 2014
Copper futures and swap contracts [Member] | Fair Value Hedging [Member] | Derivatives designated as hedging instruments [Member]
Derivative [Line Items]
Open positions (in lbs except gold in oz)	54,000,000
Average contract price	3.09
Maturities through	December 2015