STOCK-BASED COMPENSATION - SUMMARY OF STOCK OPTIONS (Details)	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares) | shares	3,480,701
Granted (in shares) | shares	1,277,500
Exercised (in shares) | shares	(308,549)
Canceled and forfeited (in shares) | shares	(50,500)
Outstanding, end of period (in shares) | shares	4,399,152
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 3.10
Granted (in dollars per share) | $ / shares	7.73
Exercised (in dollars per share) | $ / shares	2.87
Canceled and forfeited (in dollars per shares) | $ / shares	6.70
Outstanding, end of period (in dollars per share) | $ / shares	$ 4.42