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RETIREMENT FUND AND PROFIT SHARING PLAN, Employees' Savings Plan (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Compensation Expenses [Abstract] |  |
Employer match of the first 1% of compensation contributed by participants | 100.00% |
Percentage of participant contribution under condition one | 1.00% |
Employer match of the next 5% compensation contributed by participants, percentage | 50.00% |
Percentage of employee deferrals under condition two | 5.00% |
UNITED STATES | Common Class A [Member] |  |
Compensation Expenses [Abstract] |  |
Shares owned by plan (in shares) | 114,839 |
UNITED STATES | Common Class B [Member] |  |
Compensation Expenses [Abstract] |  |
Shares owned by plan (in shares) | 127,733 |
HONG KONG |  |
Compensation Expenses [Abstract] |  |
Employer matching contribution, percentage | 7.00% |
HONG KONG | Minimum [Member] |  |
Compensation Expenses [Abstract] |  |
Employer matching contribution, percentage | 5.00% |
HONG KONG | Maximum [Member] |  |
Compensation Expenses [Abstract] |  |
Employee matching contribution per participant under prior plan | 5.00% |
Retirement Fund [Member] | HONG KONG |  |
Compensation Expenses [Abstract] |  |
Compensation expenses | $ 0.3 | $ 0.3
Retirement Fund [Member] | HONG KONG | Common Class A [Member] |  |
Compensation Expenses [Abstract] |  |
Shares owned by plan (in shares) | 3,323 |
Retirement Fund [Member] | HONG KONG | Common Class B [Member] |  |
Compensation Expenses [Abstract] |  |
Shares owned by plan (in shares) | 17,342 |
401K Plan [Member] | UNITED STATES |  |
Compensation Expenses [Abstract] |  |
Compensation expenses | $ 1.3 | $ 1.2

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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