ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Accrued expenses and other current liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued compensation expense and related costs	$ 67,034	$ 33,404
Deferred revenue	4,498	3,319
Other current liabilities and accrued expenses	18,280	13,172
Total	$ 89,812	$ 49,895