Summary of Significant Accounting Policies - Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from calculation of diluted net loss per share	6,723,238	5,612,389	6,723,238	5,612,389
Stock Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from calculation of diluted net loss per share	6,314,838	5,612,389	6,314,838	5,612,389
Unvested Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common shares excluded from calculation of diluted net loss per share	408,400		408,400