Net Loss per Share - Anti-Dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Anti-dilutive securities excluded from computation of earnings per share
Total, anti-dilutive securities excluded from computation of earnings per share	10,164,170	8,820,030	6,838,158
Stock options
Anti-dilutive securities excluded from computation of earnings per share
Total, anti-dilutive securities excluded from computation of earnings per share	9,958,858	8,491,734	5,960,939
Restricted shares
Anti-dilutive securities excluded from computation of earnings per share
Total, anti-dilutive securities excluded from computation of earnings per share			877,219
Restricted Share Units (RSUs)
Anti-dilutive securities excluded from computation of earnings per share
Total, anti-dilutive securities excluded from computation of earnings per share	205,312	328,296