Net Loss Per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss	$ (7,057)	$ (7,935)	$ (20,804)	$ (24,904)
Dividend attributable to down round feature of warrants			(303)	(359)
Dividend attributable to Series A & B convertible preferred stock			(372)
Series A & B convertible preferred stock - beneficial conversion feature			(9,399)
Net loss attributable to common stockholders for basic and diluted loss per share	$ (7,057)	$ (7,935)	$ (30,878)	$ (25,263)
Denominator:
Weighted average number of common shares outstanding - basic and diluted (in shares)	76,321,644	23,923,196	53,548,902	22,039,386
Net loss per share attributable to common stockholders - basic and diluted (in dollars per share)	$ (0.09)	$ (0.33)	$ (0.58)	$ (1.15)
Exercise of the pre-funded warrants			16,663,902