Net Loss Per Common Share - Schedule of Potentially Dilutive Securities Excluded from Diluted Net Loss Per Common Share (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	1,992,347	1,928,586
Options to purchase common stock
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	1,796,103	1,766,959
Restricted stock units
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	168,408	66,630
Common stock subject to repurchase
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share		67,307
Common stock warrants
Antidilutive Securities
Potentially dilutive securities excluded from diluted net loss per common share	27,836	27,690