Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Class A [Member] Retained Earnings [Member]	Common Class A [Member] AOCI Attributable to Parent [Member]	Common Class A [Member] Common Stock, Common Class A [Member]	Common Class A [Member] Common Stock, Common Class B [Member]	Common Class A [Member] Additional Paid-in Capital [Member]	Common Class A [Member]	Common Class B [Member] Retained Earnings [Member]	Common Class B [Member] AOCI Attributable to Parent [Member]	Common Class B [Member] Common Stock, Common Class A [Member]	Common Class B [Member] Common Stock, Common Class B [Member]	Common Class B [Member] Additional Paid-in Capital [Member]	Common Class B [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] AOCI Attributable to Parent [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock, Common Class A [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock, Common Class B [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Common Stock, Common Class A [Member]	Common Stock, Common Class B [Member]	Additional Paid-in Capital [Member]	Total
Balance at Dec. 31, 2018													$ 463	$ (463)	$ 0	$ 0	$ 0	$ 0	$ 168,695	$ (24,838)	$ 217	$ 1,009	$ 31,387	$ 176,470
Net earnings (loss)						$ (1,531)						$ (7,212)							(8,743)	0	0	0	0	(8,743)
Cash dividends declared on common stock	$ (518)	$ 0	$ 0	$ 0	$ 0	(518)	$ (2,834)	$ 0	$ 0	$ 0	$ 0	(2,834)
Issuance of restricted common stock																			0	0	0	7	(7)	0
Repurchase of Class A common stock																			0	0	(3)	0	(445)	(448)
Forfeiture of restricted common stock																			0	0	0	(3)		0
Forfeiture of restricted common stock, APIC																							3
Foreign currency translation adjustment, net of taxes																			0	2,603	0	0	0	2,603
Stock-based compensation expense																			0	0	0	0	2,888	2,888
Change in unfunded SERP liability, net of taxes																			0	(1,367)	0	0	0	(1,367)
Unrealized holding losses on marketable securities arising during the year, net of taxes of $7																								0
Balance at Dec. 31, 2019																			157,063	(24,065)	214	1,013	33,826	168,051
Net earnings (loss)						2,089						10,706							12,795	0	0	0	0	12,795
Cash dividends declared on common stock	$ (515)	$ 0	$ 0	$ 0	$ 0	$ (515)	$ (2,852)	$ 0	$ 0	$ 0	$ 0	$ (2,852)
Issuance of restricted common stock																			0	0	0	11	(11)	0
Forfeiture of restricted common stock																			0	0	0	(3)		0
Forfeiture of restricted common stock, APIC																							3
Foreign currency translation adjustment, net of taxes																			0	6,890	0	0	0	6,890
Stock-based compensation expense																			0	0	0	0	2,318	2,318
Change in unfunded SERP liability, net of taxes																			0	(895)	0	0	0	(895)
Unrealized holding losses on marketable securities arising during the year, net of taxes of $7																			0	7	0	0	0	7
Balance at Dec. 31, 2020																			$ 166,491	$ (18,063)	$ 214	$ 1,021	$ 36,136	$ 185,799