Consolidated Statements of Stockholders' Equity - USD ($)	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2014	$ 48,549,691	$ (448,421)	$ 682,320	$ 50,366,546	$ (37,673,289)	$ 61,476,847
Net income	5,716,767					5,716,767
Change in unrealized gain on available-for-sale securities and effect of interest rate swaps, net of income taxes		(235,535)				(235,535)
Dividends on common stock	(1,008,332)					(1,008,332)
Stock award plans				(108,631)	394,220	285,589
Stock options exercised			3,580	183,549		187,129
Balance at Dec. 31, 2015	53,258,126	(683,956)	685,900	50,441,464	(37,279,069)	66,422,465
Net income	5,594,011					5,594,011
Change in unrealized gain on available-for-sale securities and effect of interest rate swaps, net of income taxes		(625,285)				(625,285)
Dividends on common stock	(1,504,855)					(1,504,855)
Stock award plans				26,463	347,319	373,782
Stock options exercised			1,650	84,150		85,800
Treasury stock purchased					(371,538)	(371,538)
Balance at Dec. 31, 2016	57,347,282	(1,309,241)	687,550	50,552,077	(37,303,288)	69,974,380
Net income	5,157,664					5,157,664
Change in unrealized gain on available-for-sale securities and effect of interest rate swaps, net of income taxes		1,103,048				1,103,048
Dividends on common stock	(1,857,456)					(1,857,456)
Stock award plans				288,722	177,747	466,469
Stock options exercised			300	15,270		15,570
Reclassification of amounts within AOCI to retained earnings due to tax reform	31,818					31,818
Balance at Dec. 31, 2017	$ 60,679,308	$ (206,193)	$ 687,850	$ 50,856,069	$ (37,125,541)	$ 74,891,493