Net Income (Loss) Per Share Attributable to Common Stockholders - Additional Information (Detail) - shares |
3 Months Ended | 9 Months Ended | |
|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Stock Option [Member] | |||
| Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] | |||
| Number of anti-dilutive securities excluded from computation of earnings per share | 2,400,000 | ||
| Weighted Average [Member] | Stock Option [Member] | |||
| Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] | |||
| Number of anti-dilutive securities excluded from computation of earnings per share | 100,000 | 3,348,632 | 898,962 |
| Weighted Average [Member] | Warrants to Purchase Common Stock [Member] | |||
| Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] | |||
| Number of anti-dilutive securities excluded from computation of earnings per share | 300,000 | 317,562 | 317,562 |