Summary of Warrant Activity (Detail) - Warrants - $ / shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Shares | |||
| Beginning Balance | 10,093,836 | 10,093,836 | 1,697,974 |
| Granted | 2,035,398 | 9,205,862 | |
| Exercised | (200,000) | ||
| Forfeited, cancelled, or expired | (722,974) | (610,000) | |
| Ending Balance | 11,406,260 | 10,093,836 | 10,093,836 |
| Warrants exercisable, December 31, 2016 | 9,235,862 | ||
| Weighted-Average Exercise Price Per Share | |||
| Beginning Balance | $ 4.18 | $ 4.18 | $ 5.44 |
| Granted | 2.00 | 4.00 | |
| Exercised | 2.00 | ||
| Forfeited, cancelled, or expired | 6.50 | 5.71 | |
| Ending Balance | 3.64 | $ 4.18 | $ 4.18 |
| Warrants exercisable, December 31, 2016 | $ 4.00 | ||