Balance Sheet Components - Accrued Liabilities (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Payables And Accruals [Abstract] | ||
| Payroll and related | $ 3,818 | $ 2,296 |
| Preclinical and clinical | 8,803 | 4,376 |
| Professional services | 114 | 69 |
| Other | 164 | 415 |
| Total | $ 12,899 | $ 7,156 |