CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY - USD ($)	Additional paid-in capital [Member]	Retained earnings [Member]	Treasury stock [Member]	Accumulated other comprehensive loss [Member]	Common Class A [Member]	Total
Balance at Dec. 31, 2017	$ 13,064,000	$ 34,455,000	$ (5,179,000)	$ (530,000)	$ 4,203,000	$ 46,013,000
Balance (in shares) at Dec. 31, 2017			(631,000)		4,203,000
Net income	0	911,000	$ 0	0	$ 0	911,000
Exercise of stock options	553,000	0	$ 0	0	$ 184,000	737,000
Exercise of stock options (in shares)			0		184,000
Restricted common stock compensation	25,000	0	$ 0	0	$ 7,000	32,000
Restricted common stock compensation (in shares)			0		7,000
Purchase of Class A common stock	0	0	$ (589,000)	0	$ 0	(589,000)
Purchase of Class A common stock (in shares)			(71,000)		0
Stock-based compensation	169,000	0	$ 0	0	$ 0	169,000
Dividends	0	(544,000)	0	0	0	(544,000)
Foreign currency translation adjustment	0	0	0	(91,000)	0	(91,000)
Balance at Sep. 30, 2018	13,811,000	34,822,000	$ (5,768,000)	(621,000)	$ 4,394,000	46,638,000
Balance (in shares) at Sep. 30, 2018			(702,000)		4,394,000
Balance at Jun. 30, 2018	13,748,000	34,466,000	$ (5,609,000)	(589,000)	$ 4,394,000	46,410,000
Balance (in shares) at Jun. 30, 2018			(683,000)		4,394,000
Net income	0	541,000	$ 0	0	$ 0	541,000
Restricted common stock compensation	14,000	0	$ 0	0	$ 0	14,000
Restricted common stock compensation (in shares)			0		0
Purchase of Class A common stock	0	0	$ (159,000)	0	$ 0	(159,000)
Purchase of Class A common stock (in shares)			(19,000)		0
Stock-based compensation	49,000	0	$ 0	0	$ 0	49,000
Dividends	0	(185,000)	0	0	0	(185,000)
Foreign currency translation adjustment	0	0	0	(32,000)	0	(32,000)
Balance at Sep. 30, 2018	13,811,000	34,822,000	$ (5,768,000)	(621,000)	$ 4,394,000	46,638,000
Balance (in shares) at Sep. 30, 2018			(702,000)		4,394,000
Balance at Dec. 31, 2018	13,904,000	34,588,000	$ (6,695,000)	(672,000)	$ 4,410,000	45,535,000
Balance (in shares) at Dec. 31, 2018			(816,000)		4,410,000
Net income	0	5,798,000	$ 0	0	$ 0	5,798,000
Restricted common stock compensation	33,000	0	$ 0	0	$ 6,000	39,000
Restricted common stock compensation (in shares)			0		6,000
Purchase of Class A common stock	0	0	$ (3,518,000)	0	$ 0	(3,518,000)
Purchase of Class A common stock (in shares)			(457,000)		0
Stock-based compensation	89,000	0	$ 0	0	$ 0	89,000
Dividends	0	(474,000)	0	0	0	(474,000)
Foreign currency translation adjustment	0	0	0	(85,000)	0	(85,000)
Balance at Sep. 30, 2019	14,026,000	39,912,000	$ (10,213,000)	(757,000)	$ 4,416,000	47,384,000
Balance (in shares) at Sep. 30, 2019			(1,273,000)		4,416,000
Balance at Jun. 30, 2019	13,986,000	39,933,000	$ (10,162,000)	(679,000)	$ 4,416,000	47,494,000
Balance (in shares) at Jun. 30, 2019			(1,266,000)		4,416,000
Net income	0	136,000	$ 0	0	$ 0	136,000
Restricted common stock compensation	13,000	0	$ 0	0	$ 0	13,000
Restricted common stock compensation (in shares)			0		0
Purchase of Class A common stock	0	0	$ (51,000)	0	$ 0	(51,000)
Purchase of Class A common stock (in shares)			(7,000)		0
Stock-based compensation	27,000	0	$ 0	0	$ 0	27,000
Dividends	0	(157,000)	0	0	0	(157,000)
Foreign currency translation adjustment	0	0	0	(78,000)	0	(78,000)
Balance at Sep. 30, 2019	$ 14,026,000	$ 39,912,000	$ (10,213,000)	$ (757,000)	$ 4,416,000	$ 47,384,000
Balance (in shares) at Sep. 30, 2019			(1,273,000)		4,416,000