OTHER NON-CURRENT ASSETS (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Assets, Noncurrent Disclosure [Abstract]
Escrow deposit	$ 28,750	$ 28,750
Deferred contract costs	12,345	9,089	$ 8,952
Other	18,349	2,589
Total other non-current assets	$ 59,444	$ 40,428