Net Loss Per Common Share - Calculation of diluted net loss per share (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Income (Loss) Per Common Share
Total potential dilutive shares (in shares)	13,054,817	4,923,895	5,349,428
Warrant
Net Income (Loss) Per Common Share
Total potential dilutive shares (in shares)	0	0	8,230
Stock Options
Net Income (Loss) Per Common Share
Total potential dilutive shares (in shares)	4,176,518	4,677,929	5,303,723
Unvested RSUs
Net Income (Loss) Per Common Share
Total potential dilutive shares (in shares)	401,234	245,966	37,475
Employee Stock
Net Income (Loss) Per Common Share
Total potential dilutive shares (in shares)	16,828	0	0
Convertible Debt Securities
Net Income (Loss) Per Common Share
Total potential dilutive shares (in shares)	8,460,237	0	0