Net Loss Per Share - Schedule of potentially diluted securities excluded from the computation of diluted weighted-average shares outstanding (Details ) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options to purchase common stock
Net Loss Per Share
Potentially dilutive securities excluded from the computation of diluted weighted-average shares outstanding (in shares)	4,834,255	5,462,787	5,647,895
Warrants
Net Loss Per Share
Potentially dilutive securities excluded from the computation of diluted weighted-average shares outstanding (in shares)	0	120,532	605,415
Restricted stock units
Net Loss Per Share
Potentially dilutive securities excluded from the computation of diluted weighted-average shares outstanding (in shares)	614,273	227,088	146,451
Performance units
Net Loss Per Share
Potentially dilutive securities excluded from the computation of diluted weighted-average shares outstanding (in shares)	79,000	0	0