Operating Segment and Geographical Information (Details) - HKD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Segment Reporting Information [Line Items] | ||
| Total assets | $ 780,263 | $ 793,599 |
| Total liabilities | 10,933 | 11,975 |
| PRC [Member] | ||
| Segment Reporting Information [Line Items] | ||
| Total assets | 286,729 | 189,055 |
| Total liabilities | 7,263 | 143 |
| Hong Kong [Member] | ||
| Segment Reporting Information [Line Items] | ||
| Total assets | 489,450 | 600,460 |
| Total liabilities | 3,670 | 11,832 |
| The United States [Member] | ||
| Segment Reporting Information [Line Items] | ||
| Total assets | $ 3,646 | $ 3,646 |