Net Loss Per Share - Summary of Potentially Dilutive Securities Outstanding Excluded from Computation of Diluted Weighted-average Shares Outstanding (Details) - shares	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities outstanding excluded from computation of diluted weighted-average shares outstanding	3,869,651	4,317,692
Incentive Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities outstanding excluded from computation of diluted weighted-average shares outstanding	2,380,170	3,733,544
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities outstanding excluded from computation of diluted weighted-average shares outstanding	1,405,786
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential dilutive securities outstanding excluded from computation of diluted weighted-average shares outstanding	83,695	584,148