Net Loss Per Share - Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	7,615,052	4,161,074
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	7,615,052	4,153,460
Common Stock Subject to Repurchase [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares		7,614