Net Income (Loss) Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted Net Loss per Share (Detail) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	2,400,000
Options to Purchase Common Stock [Member] | Weighted Average [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	100,000	3,348,632	898,962
Restricted Stock [Member] | Weighted Average [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share		7,038	129,835
Warrants to Purchase Common Stock [Member] | Weighted Average [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total amount of anti-dilutive securities excluded from computation of earnings per share	300,000	317,562	317,562