INCOME TAXES - Reconciliation of the Statutory U.S. Federal Tax Rate to the Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Statutory U.S. federal income tax rate	21.00%	35.00%	35.00%
State income taxes, net of federal benefit	(0.20%)	0.00%	0.50%
Effect of foreign operations	(4.70%)	(7.10%)	0.90%
Accruals and reserves	0.00%	0.10%	3.20%
Nondeductible employee compensation	1.70%	1.50%	1.50%
Research tax credits	(2.70%)	(0.70%)	(1.30%)
Change in valuation allowance	0.00%	(4.10%)	(9.70%)
Stock based compensation	(2.70%)	(1.90%)	0.00%
U.S. Tax Cuts and Jobs Act	(3.50%)	7.70%	0.00%
U.S. International Tax (Sub F, GILTI, FDII)	(1.20%)	0.00%	0.00%
Other	0.80%	0.00%	(0.20%)
Effective tax rate	8.50%	30.50%	29.90%