Consolidated Statements of Stockholders' Equity - USD ($)	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earning [Member]	Treasury Stock [Member]	Total
Balances at Dec. 31, 2015	$ 7,290	$ 31,797,418	$ 19,238,610	$ (6,233,109)	$ 44,810,209
Balances (in shares) at Dec. 31, 2015	7,290,167
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon stock option exercise	$ 265	711,135	0	0	711,400
Issuance of common stock upon stock option exercise (in shares)	265,000
Stock compensation expense	$ 0	133,904	0	0	133,904
Repurchases of common stock	0	0	0	(1,048,592)	(1,048,592)
Excess tax benefits from share-based payment arrangements	0	302,783	0	0	302,783
Net income	0	0	11,372,239	0	11,372,239
Balances at Dec. 31, 2016	$ 7,555	32,945,240	30,610,849	(7,281,701)	56,281,943
Balances (in shares) at Dec. 31, 2016	7,555,167
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon stock option exercise	$ 45	395,705	0	0	395,750
Issuance of common stock upon stock option exercise (in shares)	45,000
Stock compensation expense	$ 0	127,378	0	0	127,378
Repurchases of common stock	0	0	0	(616,499)	(616,499)
Net income	0	0	11,328,266	0	11,328,266
Balances at Dec. 31, 2017	$ 7,600	33,468,323	41,939,115	(7,898,200)	$ 67,516,838
Balances (in shares) at Dec. 31, 2017	7,600,167				7,189,233
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to prior periods from adopting ASC606 | ASU 2014-09 [Member]	$ 0	0	10,184,335	0	$ 10,184,335
Issuance of common stock upon stock option exercise	$ 138	2,570,692	0	0	2,570,830
Issuance of common stock upon stock option exercise (in shares)	138,000
Stock compensation expense	$ 0	263,431	0	0	263,431
Repurchases of common stock	0	0	0	(3,000,183)	(3,000,183)
Net income	0	0	20,053,269	0	20,053,269
Balances at Dec. 31, 2018	$ 7,738	$ 36,302,446	$ 72,176,719	$ (10,898,383)	$ 97,588,520
Balances (in shares) at Dec. 31, 2018	7,738,167				7,275,902