Other Balance Sheet Accounts - Summary of Accounts Payable and Accrued Expenses (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Payables And Accruals [Abstract] | ||
| Employee compensation | $ 2,518 | $ 2,220 |
| Clinical trial accruals | 446 | 102 |
| Accounts payable | 326 | 733 |
| Deferred rent | 223 | 496 |
| Other accrued liabilities | 614 | 361 |
| Total accounts payable and accrued expenses | $ 4,127 | $ 3,912 |