COMMITMENTS AND CONTINGENCIES: (Details 3) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended	1 Months Ended		9 Months Ended		1 Months Ended				3 Months Ended		9 Months Ended	12 Months Ended	9 Months Ended
	Sep. 30, 2014 USD ($)	Dec. 31, 1997 Power purchase agreements Enersur	Jun. 30, 2014 Peruvian operations Power purchase agreements Electroperu S.A MW	Jul. 31, 2014 Peruvian operations Power purchase agreements Kallpa MW	Sep. 30, 2014 Toquepala Concentrator Expansion Copper T	Sep. 30, 2014 Toquepala Concentrator Expansion Molybdenum T	Nov. 30, 2013 Toquepala Concentrator Expansion Peruvian operations USD ($)	Nov. 30, 2013 Toquepala Concentrator Expansion Peruvian operations PEN	Feb. 28, 2013 Toquepala Concentrator Expansion Peruvian operations USD ($) item	Feb. 28, 2013 Toquepala Concentrator Expansion Peruvian operations PEN	Jun. 30, 2013 Toquepala Concentrator Expansion Peruvian operations USD ($)	Jun. 30, 2013 Toquepala Concentrator Expansion Peruvian operations PEN	Sep. 30, 2014 Mexico Generadora de Energia S. de R.L. ("MGE")	Dec. 31, 2005 Mexico Generadora de Energia S. de R.L. ("MGE") item	Sep. 30, 2014 Mexico Generadora de Energia S. de R.L. ("MGE") Mexican Operations item
Other commitments:
Number of provinces for which final agreement reached									1	1
Amount committed to funding for development projects in the Candarave province									$ 100	255
Amount paid-out for development projects in the Candarave province											17	45
Amount committed to funding for development projects in the Jorge Basadre province							36	100
Estimated increase in annual production (in tons)					100,000	3,100
Term of power purchase agreement related to sale of power plant		20 years	20 years	10 years
Number of megawatt supply energy for which the entity signed the agreement			120	120
Number of power plants														2	2
Percentage of supply to third-party energy users													12.00%
Commitment for capital projects	$ 600