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	3 Months Ended
	Dec. 31, 1997	Mar. 31, 2014 Mexican Operations USD ($)	Dec. 31, 2013 Tia Maria Peruvian operations item	Mar. 31, 2014 Tia Maria Peruvian operations USD ($)	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	Mar. 31, 2014 MGE	Dec. 31, 2005 MGE item	Mar. 31, 2014 MGE Mexican Operations item
Other commitments:
Number of work-shops successfully held			2
Total spending for the project				$ 535.4
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
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%
Commitment for capital projects		$ 235