Income Taxes - Reconciliation Between Income Taxes Computed at the Federal Statutory Income Tax Rate and the Provision for Benefit from Income Taxes (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Income Tax Disclosure [Abstract] | |||
| Federal statutory rate | 34.00% | 34.00% | 34.00% |
| Effect of: | |||
| Impact of foreign rate differential | (12.60%) | ||
| Change in valuation allowance | (24.40%) | (32.00%) | (35.40%) |
| Research and development tax credit | 0.90% | 0.80% | 2.50% |
| Stock-based compensation | (0.90%) | (2.60%) | (1.30%) |
| Other | 3.00% | (0.20%) | 0.20% |
| Total | 0.00% | 0.00% | 0.00% |