Condensed consolidated Statements of Stockholders' Equity (unaudited) - USD ($)	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earning [Member]	Treasury Stock [Member]	Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment due to adoption of ASC606 | ASU 2014-09 [Member]	$ 0	$ 0	$ 10,184,335	$ 0	$ 10,184,335
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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	159,883	0	0	159,883
Repurchases of common stock	0	0	0	(2,559,050)	(2,559,050)
Net income	0	0	13,869,585	0	13,869,585
Balances at Sep. 30, 2018	$ 7,738	36,198,898	65,993,035	(10,457,250)	91,742,421
Balances (in shares) at Sep. 30, 2018	7,738,167
Balances at Jun. 30, 2018	$ 7,655	34,424,632	60,949,985	(7,898,200)	87,484,072
Balances (in shares) at Jun. 30, 2018	7,655,167
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon stock option exercise	$ 83	1,710,697	0	0	1,710,780
Issuance of common stock upon stock option exercise (in shares)	83,000
Stock compensation expense	$ 0	63,569	0	0	63,569
Repurchases of common stock	0	0	0	(2,559,050)	(2,559,050)
Net income	0	0	5,043,050	0	5,043,050
Balances at Sep. 30, 2018	$ 7,738	36,198,898	65,993,035	(10,457,250)	91,742,421
Balances (in shares) at Sep. 30, 2018	7,738,167
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon stock option exercise	$ 73	2,133,323	0	0	$ 2,133,396
Issuance of common stock upon stock option exercise (in shares)	73,063
Stock compensation expense	$ 0	520,387	0	0	520,387
Repurchases of common stock	0	0	0	(357,289)	(357,289)
Net income	0	0	17,115,988	0	17,115,988
Balances at Sep. 30, 2019	$ 7,811	38,956,156	89,292,707	(11,255,672)	$ 117,001,002
Balances (in shares) at Sep. 30, 2019	7,811,230				7,342,756
Balances at Jun. 30, 2019	$ 7,796	38,299,800	83,019,774	(11,016,949)	$ 110,310,421
Balances (in shares) at Jun. 30, 2019	7,796,230
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon stock option exercise	$ 15	396,435	0	0	396,450
Issuance of common stock upon stock option exercise (in shares)	15,000
Stock compensation expense	$ 0	259,921	0	0	259,921
Repurchases of common stock	0	0	0	(238,723)	(238,723)
Net income	0	0	6,272,933	0	6,272,933
Balances at Sep. 30, 2019	$ 7,811	$ 38,956,156	$ 89,292,707	$ (11,255,672)	$ 117,001,002
Balances (in shares) at Sep. 30, 2019	7,811,230				7,342,756