CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($)	Common Class A [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Treasury stock [Member]	Accumulated other comprehensive loss [Member]	Total
Balance at Dec. 31, 2017	$ 4,203,000	$ 13,064,000	$ 34,455,000	$ (5,179,000)	$ (530,000)	$ 46,013,000
Balance (in shares) at Dec. 31, 2017	4,203,000			(631,000)
Net income	$ 0	0	856,000	$ 0	0	856,000
Exercise of stock options	$ 200,000	606,000	0	0	0	806,000
Exercise of stock options (in shares)	200,000
Restricted common stock compensation	$ 7,000	38,000	0	0	0	45,000
Restricted common stock compensation (in shares)	7,000
Stock-based compensation	$ 0	196,000	0	0	0	196,000
Purchase of Class A common stock	$ 0	0	0	$ (1,516,000)	0	(1,516,000)
Purchase of Class A common stock (in shares)	0			(185,000)
Dividends	$ 0	0	(723,000)	$ 0	0	(723,000)
Foreign currency translation adjustment	0	0	0	0	(142,000)	(142,000)
Balance at Dec. 31, 2018	$ 4,410,000	13,904,000	34,588,000	$ (6,695,000)	(672,000)	45,535,000
Balance (in shares) at Dec. 31, 2018	4,410,000			(816,000)
Net income	$ 0	0	4,911,000	$ 0	0	4,911,000
Restricted common stock compensation	$ 6,000	46,000	0	0	0	52,000
Restricted common stock compensation (in shares)	6,000
Stock-based compensation	$ 0	106,000	0	0	0	106,000
Purchase of Class A common stock	$ 0	0	0	$ (3,518,000)	0	(3,518,000)
Purchase of Class A common stock (in shares)	0			(457,000)
Dividends	$ 0	0	(632,000)	$ 0	0	(632,000)
Foreign currency translation adjustment	0	0	0	0	52,000	52,000
Balance at Dec. 31, 2019	$ 4,416,000	$ 14,056,000	$ 38,867,000	$ (10,213,000)	$ (620,000)	$ 46,506,000
Balance (in shares) at Dec. 31, 2019	4,416,000			(1,273,000)