NET INCOME (LOSS) PER SHARE - OUTSTANDING SECURITIES (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)	551,000
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)		3,616,995
Restricted stock awards outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)		77,540
RSUs outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)		403,935
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase shares of common stock (in shares)		11,889