Net Loss Per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	$ (32,900)	$ (23,138)
Dividend attributable to down round feature of warrants	(359)
Net loss attributable to common stockholders	(33,259)	(23,138)
Change in fair value of warrant liability		7,284
Net loss attributable to common stockholders for diluted loss per share	$ (33,259)	$ (30,422)
Denominator:
Weighted average number of common shares outstanding - basic (in shares)	22,582,687	14,144,287
Assumed conversion of dilutive securities:
Private Placement Warrants (in shares)		268,408
Denominator for diluted loss per share - adjusted weighted (in shares)	22,582,687	14,412,695
Net loss per share attributable to common stockholders - basic (in dollars per share)	$ (1.47)	$ (1.64)
Net loss per share attributable to common stockholders - diluted (in dollars per share)	$ (1.47)	$ (2.11)