STOCK BASED COMPENSATION - Exercise price (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options outstanding, number | shares	9,494,712
Options outstanding, remaining term	8 years 18 days
Options outstanding, exercise price	$ 12.00
Options exercisable, number | shares	4,548,959
Options exercisable, remaining term	6 years 11 months 12 days
Options exercisable, exercise price	$ 9.61
$5.05 to $5.87
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	5.05
Options exercise price, upper limit	$ 5.87
Options outstanding, number | shares	1,086,300
Options outstanding, remaining term	6 years 8 months 16 days
Options outstanding, exercise price	$ 5.56
Options exercisable, number | shares	945,048
Options exercisable, remaining term	6 years 7 months 24 days
Options exercisable, exercise price	$ 5.56
$5.88 - $7.55
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	5.88
Options exercise price, upper limit	$ 7.55
Options outstanding, number | shares	1,413,645
Options outstanding, remaining term	6 years 6 months 26 days
Options outstanding, exercise price	$ 7.25
Options exercisable, number | shares	1,329,098
Options exercisable, remaining term	6 years 6 months 4 days
Options exercisable, exercise price	$ 7.28
$7.56 - $9.10
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	7.56
Options exercise price, upper limit	$ 9.10
Options outstanding, number | shares	970,107
Options outstanding, remaining term	6 years 10 months 13 days
Options outstanding, exercise price	$ 8.44
Options exercisable, number | shares	830,055
Options exercisable, remaining term	6 years 7 months 6 days
Options exercisable, exercise price	$ 8.45
$9.11 - $10.69
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	9.11
Options exercise price, upper limit	$ 10.69
Options outstanding, number | shares	962,900
Options outstanding, remaining term	8 years 8 months 8 days
Options outstanding, exercise price	$ 9.70
Options exercisable, number | shares	248,689
Options exercisable, remaining term	7 years 7 months 6 days
Options exercisable, exercise price	$ 9.44
$10.70 - $11.15
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	10.70
Options exercise price, upper limit	$ 11.15
Options outstanding, number | shares	118,950
Options outstanding, remaining term	6 years 5 months 5 days
Options outstanding, exercise price	$ 11.06
Options exercisable, number | shares	88,750
Options exercisable, remaining term	5 years 5 months 12 days
Options exercisable, exercise price	$ 11.05
$11.16 - $11.26
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	11.16
Options exercise price, upper limit	$ 11.26
Options outstanding, number | shares	1,574,900
Options outstanding, remaining term	9 years 2 months 1 day
Options outstanding, exercise price	$ 11.26
Options exercisable, remaining term	0 years
$11.27 - $16.50
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	$ 11.27
Options exercise price, upper limit	$ 16.50
Options outstanding, number | shares	1,283,110
Options outstanding, remaining term	8 years 2 months 19 days
Options outstanding, exercise price	$ 14.93
Options exercisable, number | shares	719,738
Options exercisable, remaining term	7 years 11 months 12 days
Options exercisable, exercise price	$ 15.23
$16.51 - $19.75
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	16.51
Options exercise price, upper limit	$ 19.75
Options outstanding, number | shares	1,046,000
Options outstanding, remaining term	8 years 8 months 8 days
Options outstanding, exercise price	$ 17.62
Options exercisable, number | shares	378,581
Options exercisable, remaining term	8 years 1 month 13 days
Options exercisable, exercise price	$ 17.33
$19.76 - $25.78
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	19.76
Options exercise price, upper limit	$ 25.78
Options outstanding, number | shares	994,800
Options outstanding, remaining term	9 years 7 months 28 days
Options outstanding, exercise price	$ 21.79
Options exercisable, remaining term	0 years
$25.79 - 117.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options exercise price, lower limit	$ 25.79
Options exercise price, upper limit	$ 117.00
Options outstanding, number | shares	44,000
Options outstanding, remaining term	8 years 3 months 11 days
Options outstanding, exercise price	$ 42.15
Options exercisable, number | shares	9,000
Options exercisable, remaining term	1 year 8 months 23 days
Options exercisable, exercise price	$ 99.12