Net Loss Per Share of Common Stock - Schedule of Antidilutive Securities Excluded from Computation of Diluted Weighted Average Shares Outstanding (Detail) - shares |
9 Months Ended | |
|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Potentially antidilutive securities outstanding excluded from the computation of diluted weighted average shares | 38,513,380 | 42,287,087 |
| Employee Stock Options [Member] | ||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Potentially antidilutive securities outstanding excluded from the computation of diluted weighted average shares | 7,248,198 | 6,016,984 |
| Warrants [Member] | ||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Potentially antidilutive securities outstanding excluded from the computation of diluted weighted average shares | 31,265,182 | 36,270,103 |