Income Taxes - Reconciliation of Federal Statutory Income Tax Rate and Effective Income Tax Rate (Detail) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Income Tax Disclosure [Abstract] | ||
| Federal statutory rate | 34.00% | 34.00% |
| Change in valuation allowance | (1.60%) | (1.60%) |
| State income taxes, net of federal effect | 5.80% | 5.80% |
| Research and development credits | 4.10% | 5.00% |
| Removal of net operating loss and other credits | (39.20%) | (41.20%) |
| Stock compensation and other permanent items | (3.10%) | (2.00%) |
| Effective income tax rate | 0.00% | 0.00% |