COMMITMENTS AND CONTINGENCIES: (Details 3) In Millions, unless otherwise specified	12 Months Ended	3 Months Ended	1 Months Ended				3 Months Ended		12 Months Ended
	Dec. 31, 1997	Dec. 31, 2013 Tia Maria Peruvian operations USD ($) item	Nov. 30, 2013 Toquepala Concentrator Expansion Peruvian operations USD ($)	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	Dec. 31, 2013 MGE	Dec. 31, 2005 MGE item	Dec. 31, 2013 MGE Mexican Operations item
Other commitments:
Number of work-shops successfully held		2
Total spending for the project		$ 534.6
Equipment reassigned to other operations, carrying value		189.5
Term of power purchase agreement related to sale of power plant	20 years
Number of provinces for which final agreement reached					1	1
Number of provinces neighboring the Toquepala unit					3	3
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
Number of power plants										2	2
Number of power plants completed											1
Percentage of supply to third-party energy users									12.00%