CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Class A Common Stock [Member]	Class B Common Stock [Member]	Retained Earnings [Member]	Retained Earnings [Member] Class A Common Stock [Member]	Retained Earnings [Member] Class B Common Stock [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Common Stock [Member] Class A Common Stock [Member]	Common Stock [Member] Class B Common Stock [Member]	Additional Paid-in Capital [Member]
Balance at Dec. 31, 2016	$ 158,434			$ 161,287			$ (31,297)	$ 217	$ 985	$ 27,242
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends declared on common stock		$ (522)	$ (2,757)		$ (522)	$ (2,757)
Issuance of restricted common stock	0								5	(5)
Forfeiture of restricted common stock	0								(4)	4
Foreign currency translation adjustment, net of taxes	12,439						12,439
Unrealized holding losses on marketable securities arising during the year, net of taxes	(279)						(279)
Stock-based compensation expense	3,030									3,030
Change in unfunded SERP liability, net of taxes	(488)						(488)
Reclassification of APIC pool upon adoption of ASU 2016-09 | ASU 2016-09 [Member]	0			1,696						(1,696)
Net earnings (loss)	(11,897)	(2,113)	(9,784)	(11,897)
Balance at Dec. 31, 2017	157,960			147,807			(19,625)	217	986	28,575
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of adoption of ASU 2014-09 (Topic 606) | ASU 2014-09 [Member]	3,497			3,497
Cash dividends declared on common stock		(522)	(2,796)		$ (522)	$ (2,796)
Issuance of restricted common stock	0								26	(26)
Forfeiture of restricted common stock	0								(3)	3
Foreign currency translation adjustment, net of taxes	(6,098)						(6,098)
Unrealized holding losses on marketable securities arising during the year, net of taxes	(133)						(133)
Stock-based compensation expense	2,835									2,835
Change in unfunded SERP liability, net of taxes	1,018						1,018
Net earnings (loss)	20,709	$ 3,521	$ 17,188	20,709
Balance at Dec. 31, 2018	$ 176,470			$ 168,695			$ (24,838)	$ 217	$ 1,009	$ 31,387