Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Class A [Member] Retained Earnings [Member]	Common Class A [Member] Common Stock [Member]	Common Class A [Member]	Common Class B [Member] Retained Earnings [Member]	Common Class B [Member] Common Stock [Member]	Common Class B [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Additional Paid-in Capital [Member]	Total
Balance at Dec. 31, 2017		$ 217			$ 986		$ 147,807	$ (19,625)	$ 28,575	$ 157,960
Net earnings (loss)							(1,303)			(1,303)
Dividends declared	$ (130)		$ (130)	$ (700)		$ (700)
Forfeiture of restricted common stock					(1)
Forfeiture of restricted common stock, APIC									1
Currency translation adjustment, net of taxes								4,017		4,017
Stock-based compensation expense									779	779
Change in unfunded SERP liability, net of taxes								86		86
Unrealized losses on marketable securities arising during the period, net of taxes								(31)		(31)
Balance at Mar. 31, 2018							149,171	(15,553)		164,175
Balance at Dec. 31, 2017		217			986		147,807	(19,625)	28,575	157,960
Net earnings (loss)			2,852			13,832				16,684
Dividends declared			(391)			(2,079)
Currency translation adjustment, net of taxes										(4,463)
Change in unfunded SERP liability, net of taxes										256
Unrealized losses on marketable securities arising during the period, net of taxes										(201)
Balance at Sep. 30, 2018		217			1,007		165,518	(24,033)	30,602	173,311
Effect of adoption of ASU							3,497			3,497
Balance at Mar. 31, 2018							149,171	(15,553)		164,175
Net earnings (loss)							6,634			6,634
Dividends declared	(131)		(131)	(689)		(689)
Forfeiture of restricted common stock					(1)
Forfeiture of restricted common stock, APIC									1
Currency translation adjustment, net of taxes								(7,448)		(7,448)
Stock-based compensation expense									671	671
Change in unfunded SERP liability, net of taxes								85		85
Balance at Jun. 30, 2018		217			984		154,985	(22,916)	30,027	163,297
Net earnings (loss)			1,942			9,410	11,352			11,352
Dividends declared	(130)		(130)	(689)		(689)
Forfeiture of restricted common stock					(1)
Forfeiture of restricted common stock, APIC									1
Currency translation adjustment, net of taxes								(1,032)		(1,032)
Stock-based compensation expense										598
Change in unfunded SERP liability, net of taxes										85
Issuance of restricted common stock					24				(24)
Unrealized losses on marketable securities arising during the period, net of taxes								(170)		(170)
Balance at Sep. 30, 2018		217			1,007		165,518	(24,033)	30,602	173,311
Balance at Dec. 31, 2018		217			1,009		168,695	(24,838)	31,387	176,470
Net earnings (loss)							1,131			1,131
Dividends declared	(130)		(130)	(708)		(708)
Forfeiture of restricted common stock					(1)
Forfeiture of restricted common stock, APIC									1
Currency translation adjustment, net of taxes								540		540
Stock-based compensation expense									813	813
Change in unfunded SERP liability, net of taxes								37		37
Balance at Mar. 31, 2019		217			1,008		169,451	(24,724)	32,201	178,153
Balance at Dec. 31, 2018		217			1,009		168,695	(24,838)	31,387	176,470
Net earnings (loss)			(442)			(1,949)				(2,391)
Dividends declared			(392)			(2,124)
Currency translation adjustment, net of taxes										(2,854)
Change in unfunded SERP liability, net of taxes										111
Unrealized losses on marketable securities arising during the period, net of taxes
Balance at Sep. 30, 2019		214			1,013		164,252	(28,045)	33,206	170,640
Effect of adoption of ASU							463	(463)
Balance at Mar. 31, 2019		217			1,008		169,451	(24,724)	32,201	178,153
Net earnings (loss)							2,967			2,967
Dividends declared	(131)		(131)	(704)		(704)
Forfeiture of restricted common stock					(1)
Forfeiture of restricted common stock, APIC									1
Currency translation adjustment, net of taxes								(834)		(834)
Stock-based compensation expense									788	788
Change in unfunded SERP liability, net of taxes								37		37
Issuance of restricted common stock					7				(7)
Balance at Jun. 30, 2019		217			1,014		171,583	(25,521)	32,983	180,276
Net earnings (loss)			(1,112)			(5,378)	(6,490)			(6,490)
Dividends declared	$ (131)		$ (131)	$ (710)		$ (710)
Forfeiture of restricted common stock					(1)
Forfeiture of restricted common stock, APIC									1
Currency translation adjustment, net of taxes								(2,561)		(2,561)
Stock-based compensation expense									667	667
Change in unfunded SERP liability, net of taxes								37		37
Repurchase of Class A common stock		(3)							(445)	(448)
Unrealized losses on marketable securities arising during the period, net of taxes
Balance at Sep. 30, 2019		$ 214			$ 1,013		$ 164,252	$ (28,045)	$ 33,206	$ 170,640