Financial Instruments (Unaudited) Not Designated as Hedging Instruments (Details)	6 Months Ended
	Jun. 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)	496,000,000
Average contract price	3.08
Average market price	3.18
Maturities through	November 2014
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)	85,000
Average contract price	1,273
Average market price	1,314
Maturities through	August 2014
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)	84,000,000
Average contract price	3.07
Average market price	3.19
Maturities through	October 2014
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)	19,000,000
Average contract price	3.07
Maturities through	July 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)	53,000,000
Average contract price	3.10
Maturities through	September 2015