Net Loss Per Share - Schedule of Anti-dilutive Effect Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	3,985,523	2,861,547
Unvested Common Stock from Early Exercise of Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	88,681	219,747
Stock Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	3,896,842	2,641,800