Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Common Stock [Member] Common Class A [Member]	Common Stock [Member] Common Class B [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]	Common Class A [Member]	Common Class B [Member]	Total
Balances at Dec. 31, 2014	$ 25	$ 4	$ 44,864	$ 73,686	$ (773)	$ (30,058)			$ 87,748
Purchase of treasury stock						(2,171)			(2,171)
Issuance of shares for the exercise of stock options			406						406
Tax benefit from the exercise of options and restricted stock			240						240
Issuance of restricted common shares, net of forfeitures	1		(1)
Non-cash stock compensation expense			1,383						1,383
Dividends declared				(25,983)					(25,983)
Acquisition of non-controlling interest			(2,789)						(2,789)
Other comprehensive income (loss), foreign currency translation adjustment					(2,222)				(2,222)
Net income				17,610			$ 8,759	$ 8,851	17,610
Balances at Dec. 31, 2015	26	4	44,103	65,313	(2,995)	(32,229)			74,222
Purchase of treasury stock						(601)			(601)
Issuance of shares for the exercise of stock options			945						945
Issuance of restricted common shares, net of forfeitures
Non-cash stock compensation expense			1,929						1,929
Dividends declared				(14,324)					(14,324)
Acquisition of non-controlling interest			(252)						(252)
Other comprehensive income (loss), foreign currency translation adjustment					369				369
Net income				20,518			10,178	10,341	20,518
Balances at Dec. 31, 2016	26	4	46,725	71,507	(2,626)	(32,830)			82,806
Purchase of treasury stock						(4,123)			(4,123)
Issuance of shares for the exercise of stock options			2,455						2,455
Issuance of restricted common shares, net of forfeitures
Non-cash stock compensation expense			1,845						1,845
Dividends declared				(16,876)					(16,876)
Other comprehensive income (loss), foreign currency translation adjustment					991				991
Net income				22,943			$ 11,388	$ 11,555	22,943
Balances at Dec. 31, 2017	$ 26	$ 4	$ 51,025	$ 77,574	$ (1,635)	$ (36,953)			$ 90,041