RETIREMENT FUND AND PROFIT SHARING PLAN (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
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]
Defined Contribution Plan Disclosure [Line Items]
Shares owned by plan (in shares)	67,891
UNITED STATES | Common Class B [Member]
Defined Contribution Plan Disclosure [Line Items]
Shares owned by plan (in shares)	144,276
HONG KONG
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percentage	7.00%
HONG KONG | Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percentage	5.00%
HONG KONG | Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Employee matching contribution per participant under prior plan	5.00%
Retirement Fund [Member] | HONG KONG
Defined Contribution Plan Disclosure [Line Items]
Compensation expenses	$ 300	$ 300	$ 300
Retirement Fund [Member] | HONG KONG | Common Class A [Member]
Defined Contribution Plan Disclosure [Line Items]
Shares owned by plan (in shares)	3,323
Retirement Fund [Member] | HONG KONG | Common Class B [Member]
Defined Contribution Plan Disclosure [Line Items]
Shares owned by plan (in shares)	17,342
401K Plan [Member] | UNITED STATES
Defined Contribution Plan Disclosure [Line Items]
Compensation expenses	$ 1,200	1,100	1,200
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension expense	$ 1,700	1,600	1,500
Normal retirement age	65 years
Number of years of service	20 years
Number of years of plan participation	5 years
Percentage of average base compensation payable as normal retirement benefit under the plan	40.00%
Early retirement age	55 years
Number of consecutive calendar years of plan participation to calculate average base compensation	20 years
Number of monthly payments under the death benefit of the plan	120 months
Period for which beneficiary is entitled to receive benefit	shorter of (i) the time necessary to complete 120 monthly payments or (ii) 60 months
Percentage of participant's annual base salary received by beneficiary for one year from date of death	100.00%
Period for which beneficiary will receive hundred percent annual base salary	1 year
Percentage of participant's annual base salary received by beneficiary for years two through five following date of death	50.00%
Period for which beneficiary will receive fifty percent annual base salary	4 years
Components of SERP expense [Abstract]
Service Cost	$ 700	593	552
Interest Cost	673	659	567
Net amortization	375	391	366
Net periodic benefit cost	1,748	1,643	1,485
Summary of information about changes in plan assets, benefit obligation, and the funded status [Abstract]
Fair value of plan assets, beginning of period	0	0
Company contributions	240	129
Benefits paid	(240)	(129)
Fair value of plan assets, end of period	0	0	0
Benefit obligation January 1	16,900	15,576
Service cost	700	593	552
Interest cost	673	659	567
Benefits paid	(240)	(129)
Plan amendments	198	487
Actuarial (gains) losses	903	(286)
Benefit obligation, December 31	19,134	16,900	$ 15,576
Underfunded status, December 31	(19,134)	(16,900)
Accumulated benefit obligation	16,100	13,800
Fair value of life insurance policies and marketable securities held in a rabbi trust	14,000	12,700
Estimated net loss and prior service cost that will be amortized from accumulated other comprehensive income into net periodic benefit cost over the next fiscal year	400
Expected employer contributions in next fiscal year	300
Expected future benefit payments [Abstract]
2018	317
2019	564
2020	622
2021	622
2222	909
2023 - 2027	5,193
Amounts recognized in accumulated other comprehensive loss, pretax [Abstract]
Prior service cost	1,135	1,172
Net loss	3,732	2,970
Total amounts recognized in accumulated other comprehensive loss	$ 4,867	$ 4,142
Net periodic benefit cost [Abstract]
Discount rate	4.00%	4.25%	4.00%
Rate of compensation increase	3.00%	3.00%	3.00%
Benefit obligation [Abstract]
Discount rate	3.50%	4.00%	4.25%
Rate of compensation increase	3.00%	3.00%	3.00%
SERP [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of monthly payments entitled to beneficiary in case participant dies prior to receiving one hundred twenty monthly payments	60 months