RESTRUCTURING CHARGES - Schedule of Restructuring Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring costs
Employee compensation costs	$ 16,852	$ 13,247	$ 0
Fixed Asset disposals and accelerated depreciation of leasehold improvements	3,511	0	0
Other exit costs	238	0	0
Total restructuring costs	$ 20,601	$ 13,247	$ 0