Income Taxes - Reconciliation of Federal Statutory Income Tax Rate (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Income Tax Disclosure [Abstract] | |||
| Federal statutory income tax rate | 34.00% | 34.00% | 34.00% |
| State taxes, net of federal benefit | 3.45% | 3.45% | 3.45% |
| Permanent differences-derivative loss (gain) | (9.10%) | 0.11% | |
| Permanent differences-other | (4.66%) | 2.24% | (1.07%) |
| Research and development ("R&D") credit | 0.95% | 2.73% | 4.91% |
| Other | 0.64% | 0.61% | 0.64% |
| Increase in valuation allowance | (34.38%) | (33.93%) | (42.04%) |
| Federal statutory income tax rate, Total | 0.00% | 0.00% | 0.00% |