SUPPLEMENTAL CASH FLOW DISCLOSURES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	$ 12,755	$ 5,942	$ 5,866
Cash paid for income taxes, net of refunds	937	423	159
Purchases of PP&E and intangible assets accrued but not paid at year-end	4,364	5,238	1,641
Purchases of PP&E accrued in a prior period and paid in the current period	5,238	1,641	9,455
Distribution equivalent rights accrued, net of payments	618	1,164	372
Capitalized reclamation costs, net of amounts acquired in business combination	113	706	721
Deferred compensation expense	$ 0	$ 122	$ 6,368