RETIREMENT FUND AND PROFIT SHARING PLAN, Employees' Savings Plan (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Class A Common Stock [Member] | UNITED STATES
Compensation Expense [Abstract]
Shares owned by plan (in shares)	90,521		90,521
Class B Common Stock [Member] | UNITED STATES
Compensation Expense [Abstract]
Shares owned by plan (in shares)	140,591		140,591
401K Plan [Member] | UNITED STATES
Compensation Expense [Abstract]
Compensation expense	$ 0.3	$ 0.3	$ 0.6	$ 0.6
Retirement Fund [Member] | HONG KONG
Compensation Expense [Abstract]
Compensation expense	$ 0.1	$ 0.1	$ 0.2	$ 0.2
Retirement Fund [Member] | Class A Common Stock [Member] | HONG KONG
Compensation Expense [Abstract]
Shares owned by plan (in shares)	3,323		3,323
Retirement Fund [Member] | Class B Common Stock [Member] | HONG KONG
Compensation Expense [Abstract]
Shares owned by plan (in shares)	17,342		17,342