Segment Information - Long Lived Assets (Details) - USD ($) $ in Thousands  | 
Dec. 31, 2017  | 
Dec. 31, 2016  | 
|---|---|---|
| Segment Reporting Information [Line Items] | ||
| Long-lived assets | $ 1,149 | $ 1,388 | 
| United States | ||
| Segment Reporting Information [Line Items] | ||
| Long-lived assets | 648 | 763 | 
| Hong Kong | ||
| Segment Reporting Information [Line Items] | ||
| Long-lived assets | 78 | 140 | 
| China | ||
| Segment Reporting Information [Line Items] | ||
| Long-lived assets | 112 | 199 | 
| Other foreign countries | ||
| Segment Reporting Information [Line Items] | ||
| Long-lived assets | $ 311 | $ 286 | 
| X | ||||||||||
- Definition Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
  | 
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
  | 
| X | ||||||||||
- Details 
  | 
| X | ||||||||||
- Details 
  | 
| X | ||||||||||
- Details 
  | 
| X | ||||||||||
- Details 
  |