Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator [Abstract]
Net loss attributable to common stockholders	$ (40,179)	$ (24,664)
Denominator [Abstract]
Weighted-average common shares outstanding - basic (in shares)	61,574,405	54,883,120
Weighted-average common shares outstanding - diluted (in shares)	61,574,405	54,883,120
Net loss per share attributable to common stockholders - basic (in dollars per share)	$ (0.65)	$ (0.45)
Net loss per share attributable to common stockholders - diluted (in dollars per share)	$ (0.65)	$ (0.45)
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Warrants exercisable for common shares (in shares)	610,437	14,102
Options to purchase common shares (in shares)	10,892,830	10,538,890
Weighted average number diluted shares outstanding (in shares)	12,859,252	12,173,940
Convertible Notes 2021 [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Shares issuable upon conversion of Convertible Notes (in shares)	160,536	394,327
Convertible Notes 2022 [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Shares issuable upon conversion of Convertible Notes (in shares)	1,195,449	1,226,621