Summary of Significant Accounting Policies - Shares Excluded For EPS (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Shares excluded from the computation of diluted net loss per share
Unvested shares from share-based compensation that were anti-dilutive	4,444,344	3,700,754
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	4,239,682	3,700,754
Restricted stock units
Shares excluded from the computation of diluted net loss per share
Unvested shares from share-based compensation that were anti-dilutive	204,662