Property and Equipment, Net - Property and Equipment, Net (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | $ 9,699 | $ 8,280 |
| Less accumulated depreciation and amortization | 8,085 | 7,017 |
| Property and equipment, net | 1,614 | 1,263 |
| Computer and Office Equipment [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | 149 | 314 |
| Laboratory Equipment [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | 795 | 232 |
| Furniture and Fixtures [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | 173 | 155 |
| Software [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | 126 | |
| Leasehold Improvements [Member] | ||
| Property, Plant and Equipment [Line Items] | ||
| Property and equipment, gross | $ 8,582 | $ 7,453 |