COMMITMENTS AND CONTINGENCIES: (Details 3)	12 Months Ended	9 Months Ended	0 Months Ended		3 Months Ended		12 Months Ended	9 Months Ended
	Dec. 31, 1997	Sep. 30, 2013 Tia Maria Peruvian operations USD ($) T	Feb. 08, 2013 Toquepala Concentrator Expansion Peruvian operations USD ($) item	Feb. 08, 2013 Toquepala Concentrator Expansion Peruvian operations PEN	Jun. 30, 2013 Toquepala Concentrator Expansion Peruvian operations USD ($)	Jun. 30, 2013 Toquepala Concentrator Expansion Peruvian operations PEN	Dec. 31, 2005 MGE item	Sep. 30, 2013 MGE Mexican Operations USD ($) item
Other commitments:
Total budget for the project		$ 1,000,000,000
Estimated annual production of copper cathodes (in tons)		120,000
Total spending for the project		505,900,000
Equipment reassigned to other operations, carrying value		189,500,000
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			100,000,000	255,000,000
Amount paid-out for development projects in the Candarave province					17,000,000	45,000,000
Number of power plants							2	2
Estimated monthly capacity charge of power under power purchase agreement								$ 4,300,000