SUBSEQUENT EVENTS (Details) - Subsequent Event	Jul. 23, 2015 $ / shares	Jul. 06, 2015 USD ($) T
SUBSEQUENT EVENTS:
Quarterly cash dividend authorized | $ / shares	$ 0.10
El Pilar copper deposit
SUBSEQUENT EVENTS:
Consideration paid for acquisition		$ 100,000,000
Proven and probable reserves of copper | T		259,000,000
Average copper grade		0.30%
Average annual production of copper cathodes | T		35,000
Mine life with extraction capacity of 35000 tons of copper cathodes		13 years
Development investment		$ 300,000,000
Average life of mine cash costs per pound of copper		$ 1.60