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	$ 10	132,390	0	0	132,400
Issuance of common stock upon stock option exercise (in shares)	10,000
Stock compensation expense	$ 0	32,512	0	0	32,512
Net income	0	0	3,978,604	0	3,978,604
Balances at Mar. 31, 2018	$ 7,610	33,633,225	56,102,054	(7,898,200)	81,844,689
Balances (in shares) at Mar. 31, 2018	7,610,167
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	$ 2	58,418	0	0	$ 58,420
Issuance of common stock upon stock option exercise (in shares)	2,000
Stock compensation expense	$ 0	141,788	0	0	141,788
Net income	0	0	4,416,595	0	4,416,595
Balances at Mar. 31, 2019	$ 7,740	$ 36,502,652	$ 76,593,314	$ (10,898,383)	$ 102,205,323
Balances (in shares) at Mar. 31, 2019	7,740,167				7,277,902