COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Feb. 25, 2019
Commitments and Contingencies
Maximum future additional payments upon satisfaction of certain conditions		$ 212,000
Khoemacau
Commitments and Contingencies
Maximum future additional payments upon satisfaction of certain conditions	$ 212,000	$ 212,000
Ilovica
Commitments and Contingencies
Maximum future additional payments upon satisfaction of certain conditions	$ 163,750