STOCK-BASED COMPENSATION - SUMMARY OF STOCK OPTIONS (Details)	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares) | shares	4,634,235
Granted (in shares) | shares	225,000
Exercised (in shares) | shares	(1,277,615)
Canceled and forfeited (in shares) | shares	(225,841)
Outstanding, end of period (in shares) | shares	3,581,701
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	4.08
Exercised (in dollars per share) | $ / shares	2.43
Canceled and forfeited (in dollars per shares) | $ / shares	5.62
Outstanding, end of period (in dollars per share) | $ / shares	$ 3.25