NET LOSS PER SHARE - Calculation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net loss	$ (9,019)	$ (12,523)
Denominator:
Weighted-average shares used to compute net loss per share, basic and diluted	52,439,039	49,140,340
Basic (in dollars per share)	$ (0.17)	$ (0.25)

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.