Summary of Significant Accounting Policies - Shares Excluded For EPS (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Shares excluded from the computation of diluted net loss per share
Unvested shares from share-based compensation that were anti-dilutive	4,177,009	3,708,819
Employees stock purchase plan
Shares excluded from the computation of diluted net loss per share
Unvested shares from share-based compensation that were anti-dilutive	4,058,347	3,708,819
Restricted stock units
Shares excluded from the computation of diluted net loss per share
Unvested shares from share-based compensation that were anti-dilutive	118,662