Financial Instruments (Unaudited) Not Designated as Hedging Instruments (Details)	Mar. 31, 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)	487,000,000
Average contract price	3.21
Average market price	3.01
Maturities through	August 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)	55,000
Average contract price	1,314
Average market price	1,293
Maturities through	June 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)	66,000,000
Average contract price	3.15
Average market price	3.02
Maturities through	July 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)	7,000,000
Average contract price	3.01
Maturities through	April 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)	63,000,000
Average contract price	3.13
Maturities through	March 2015