Income Taxes - Deferred Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Deferred tax assets and liabilities: | ||
| Net operating loss and credit carryforwards | $ 9,369 | $ 7,020 |
| Deferred loss on asset sale | 2,008 | 1,935 |
| Stock-based compensation | 867 | 1,394 |
| Reserves and accruals | 809 | 1,222 |
| Research and other credits | 92 | 184 |
| Fixed assets and intangibles | (491) | (628) |
| Total gross deferred tax assets | 12,654 | 11,127 |
| Less: Valuation allowance | (12,562) | (11,373) |
| Total deferred tax assets (liabilities) | $ 92 | |
| Total deferred tax assets (liabilities) | $ (246) |