STOCK BASED COMPENSATION - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock compensation	$ 3,693	$ 3,591	$ 10,936	$ 9,881
Stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock compensation	946	918	2,831	3,103
Restricted stock units (RSUs)
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock compensation	$ 2,747	$ 2,673	$ 8,105	$ 6,778