Net Loss per Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from computation of diluted net loss per share attributable to common stockholders (in shares)	21,218,487	25,290,921
Options to Purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from computation of diluted net loss per share attributable to common stockholders (in shares)	13,181,714	23,304,831
Common Stock Issuable upon Exercise of Common Stock Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from computation of diluted net loss per share attributable to common stockholders (in shares)	450,000	898,331
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from computation of diluted net loss per share attributable to common stockholders (in shares)	6,132,421	1,087,759
Employee Stock Purchase Plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from computation of diluted net loss per share attributable to common stockholders (in shares)	1,454,352	0