NET INCOME (LOSS) PER SHARE - OUTSTANDING SECURITIES (Details) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)	2,700,000
Standard and market condition stock options outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)		3,815,784	3,661,163
Restricted stock awards outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)		44,538	77,540
RSUs outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)		627,454	527,410
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)		10,152	11,441