NET LOSS PER SHARE - Basic and diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
NET LOSS PER SHARE
Net loss (numerator)	$ (26,179)	$ (15,934)
Weighted-average shares (denominator)	39,753,583	34,193,666
Basic and diluted net loss per share (in dollars per share)	$ (0.66)	$ (0.47)

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

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