NET LOSS PER COMMON SHARE - EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Numerator:
Net loss	$ (12,369)	$ (8,730)	$ (45,513)
Denominator:
Weighted-average common stock outstanding	20,840,658	5,513,531
Net loss per share attributable to common stockholders—basic and diluted	$ (0.59)	$ (1.58)