Significant Accounting Policies - Potential Dilutive Securities Excluded from the Computation of Dilutive Weighted Average Shares Outstanding (Detail) - shares |
6 Months Ended | |
|---|---|---|
Jun. 30, 2015 |
Jun. 30, 2014 |
|
| Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Potential dilutive securities excluded from the computation of dilutive weighted average shares outstanding | 12,613,018 | 15,199,333 |
| Warrant [Member] | ||
| Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Potential dilutive securities excluded from the computation of dilutive weighted average shares outstanding | 8,896,848 | 13,602,451 |
| Stock Options [Member] | ||
| Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Potential dilutive securities excluded from the computation of dilutive weighted average shares outstanding | 3,716,170 | 1,596,882 |