Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2017	9,270,862
Balance at Dec. 31, 2017	$ 27,153	$ 6,831,271	$ (10,278,584)	$ 63,921,244	$ (962,103)	$ 59,538,981
Cumulative effect of accounting change (see Note 1) at Dec. 31, 2017				(168,311)		(168,311)
Share-based compensation (in shares)	16,648
Share-based compensation	$ 40	28,929				28,969
Purchase of treasury stock (in shares)	(72,400)
Purchase of treasury stock			(540,940)			(540,940)
Net income				1,273,619		1,273,619
Translation adjustment					21,791	21,791
Balance (in shares) at Mar. 31, 2018	9,215,110
Balance at Mar. 31, 2018	$ 27,193	6,860,200	(10,819,524)	65,026,552	(940,312)	60,154,109
Balance (in shares) at Dec. 31, 2017	9,270,862
Balance at Dec. 31, 2017	$ 27,153	6,831,271	(10,278,584)	63,921,244	(962,103)	59,538,981
Cumulative effect of accounting change (see Note 1) at Dec. 31, 2017				(168,311)		(168,311)
Net income						1,273,619
Translation adjustment						21,791
Balance (in shares) at Dec. 31, 2018	9,060,561
Balance at Dec. 31, 2018	$ 27,232	7,158,821	(11,931,850)	65,716,761	(1,510,660)	59,460,304
Cumulative effect of accounting change (see Note 1) at Dec. 31, 2018				(397,110)		(397,110)
Share-based compensation (in shares)	1,408
Share-based compensation	$ 2	185,823				185,825
Purchase of treasury stock (in shares)	(127,945)
Purchase of treasury stock			(714,617)			(714,617)
Net income				868,963		868,963
Translation adjustment					287,295	287,295
Balance (in shares) at Mar. 31, 2019	8,934,024
Balance at Mar. 31, 2019	$ 27,234	$ 7,344,644	$ (12,646,467)	$ 66,188,614	$ (1,223,365)	$ 59,690,660