Segment Reporting - Long-Lived Assets Consisting of Property and Equipment, Net by Geographic Regions (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Segment Reporting Information [Line Items] | ||
| Long-lived assets | $ 2,931 | $ 2,425 |
| United States [Member] | ||
| Segment Reporting Information [Line Items] | ||
| Long-lived assets | 2,052 | 2,425 |
| Europe [Member] | ||
| Segment Reporting Information [Line Items] | ||
| Long-lived assets | $ 879 | $ 0 |