OTHER NON-CURRENT LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Other Liabilities, Noncurrent [Abstract]
Long-term lease liabilities (see Note 8)	$ 126,843	$ 0
Accrued employee benefit liabilities	27,655	28,246
Accrued environmental remediation liabilities	26,326	27,358
Deferred consideration	10,881	20,232
Asset retirement obligations	4,337	4,349
Other	5,138	4,715
Total other non-current liabilities	$ 201,180	$ 84,900