SUPPLEMENTARY MINERAL RESERVE INFORMATION (UNAUDITED) (Details)	Dec. 31, 2014 lb
Supplementary Mineral Reserve Information [Abstract]
Long-term average price for copper used to estimate recoverable reserves (in dollars per pound)	2.00
Long-term average price for gold used to estimate recoverable reserves (in dollars per ounce)	1,000
Long-term average price for molybdenum used to estimate recoverable reserves (in dollars per pound)	10
Long-term average price for silver used to estimate recoverable reserves (in dollars per ounce)	15
Long-term average price for cobalt used to estimate recoverable reserves (in dollars per pound)	10
Three-year average London spot price for copper (per pound)	3.35
Three-year average London spot price for gold (per ounce)	1,449
Three-year average price for molybdenum (per pound)	11.50
Estimated recoverable proven and probable copper reserves in leach stockpiles (in pounds)	3,600,000,000
Estimated recoverable proven and probable copper reserves in mill stockpiles (in pounds)	900,000,000