Summary of Net Deferred Tax Assets and Net Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Income Tax Disclosure [Abstract] | ||
| Capitalized intangible assets for tax purposes | $ 47 | $ 104 |
| Reserves not currently deductible | 2,117 | 2,527 |
| Deferred revenue | 8 | 8 |
| Stock options | 4,966 | 4,072 |
| State taxes | 9 | 9 |
| Income tax credits | 2,379 | 2,471 |
| Inventory | 940 | 905 |
| Property and equipment | 201 | 345 |
| Other comprehensive income | 252 | 320 |
| Unrealized gain on foreign currency | 136 | 136 |
| Net operating losses | 43,687 | 38,753 |
| Total deferred tax assets | 54,742 | 49,650 |
| Valuation allowance | (54,310) | (49,514) |
| Net deferred tax assets | 432 | 136 |
| Capitalized intangible assets | (876) | (813) |
| Other | (354) | (61) |
| Total deferred tax liabilities | (1,230) | (874) |
| Net deferred tax liabilities | $ (798) | $ (738) |