COMMITMENTS AND CONTINGENCIES - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Property, Plant and Equipment [Line Items]
Rent expense charged to operations | $	$ 3,917	$ 3,417	$ 3,134
Corporate headquarters and laboratory facility
Property, Plant and Equipment [Line Items]
Operating lease term	2 years
Office space subject to operating lease	20,000
Corporate headquarters expansion
Property, Plant and Equipment [Line Items]
Operating lease term	2 years 3 months
Office space subject to operating lease	7,952