Other Balance Sheet Accounts - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Finite-Lived Intangible Assets [Line Items] | ||
| Net total of intangible assets | $ 810 | $ 1,300 |
| Patent application costs [Member] | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Total of summary of intangible assets | 1,500 | 2,252 |
| Accumulated amortization | $ (690) | $ (952) |