Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2015	$ 11,761,083	$ 123,282,851	$ 92,965,645	$ (2,123,829)	$ 225,885,750
Net income			6,373,489		6,373,489
Other comprehensive income, net of tax				2,525,411	2,525,411
Common cash dividends declared			(470,873)		(470,873)
Proceeds from issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	5,054	94,560			99,614
Proceeds from issuance of common stock, stock options exercised	46,020	729,473			775,493
Stock compensation expense		382,761			382,761
Tax benefit of nonqualified stock options exercised		22,508			22,508
Restricted stock awards - common stock	22,382	(22,382)
Exchange of common stock in connection with stock options exercised and restricted stock vested	(19,628)	(431,806)			(451,434)
Balance at Mar. 31, 2016	11,814,911	124,057,965	98,868,261	401,582	235,142,719
Balance at Dec. 31, 2015	11,761,083	123,282,851	92,965,645	(2,123,829)	225,885,750
Net income					13,049,956
Other comprehensive income, net of tax					3,706,044
Tax basis adjustment related to the acquisition of noncontrolling interest in m2 Lease Funds					2,132,415
Balance at Jun. 30, 2016	13,057,368	155,453,781	105,024,027	1,582,215	275,117,391
Balance at Mar. 31, 2016	11,814,911	124,057,965	98,868,261	401,582	235,142,719
Net income			6,676,467		6,676,467
Other comprehensive income, net of tax				1,180,633	1,180,633
Common cash dividends declared			(520,701)		(520,701)
Proceeds from issuance of common stock, net of issuance costs	1,215,000	28,613,916			29,828,916
Proceeds from issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	6,982	142,887			149,869
Proceeds from issuance of common stock, stock options exercised	20,975	230,671			251,646
Tax basis adjustment related to the acquisition of noncontrolling interest in m2 Lease Funds		2,132,415			2,132,415
Stock compensation expense		187,569			187,569
Tax benefit of nonqualified stock options exercised		87,858			87,858
Restricted stock awards - common stock	(500)	500
Balance at Jun. 30, 2016	13,057,368	155,453,781	105,024,027	1,582,215	275,117,391
Balance at Dec. 31, 2016	13,106,845	156,776,642	118,616,901	(2,459,589)	286,040,799
Net income			9,184,965		9,184,965
Other comprehensive income, net of tax				410,739	410,739
Common cash dividends declared			(656,574)		(656,574)
Proceeds from issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	3,573	83,091			86,664
Proceeds from issuance of common stock, stock options exercised	44,284	630,290			674,574
Stock compensation expense		388,753			388,753
Restricted stock awards - common stock	13,289	(13,289)
Exchange of common stock in connection with stock options exercised and restricted stock vested	(6,772)	(283,518)			(290,290)
Balance at Mar. 31, 2017	13,161,219	157,581,969	127,145,292	(2,048,850)	295,839,630
Balance at Dec. 31, 2016	13,106,845	156,776,642	118,616,901	(2,459,589)	286,040,799
Net income					17,950,982
Other comprehensive income, net of tax					1,112,478
Tax basis adjustment related to the acquisition of noncontrolling interest in m2 Lease Funds
Balance at Jun. 30, 2017	13,175,234	158,001,006	135,254,306	(1,347,111)	305,083,435
Balance at Mar. 31, 2017	13,161,219	157,581,969	127,145,292	(2,048,850)	295,839,630
Net income			8,766,017		8,766,017
Other comprehensive income, net of tax				701,739	701,739
Common cash dividends declared			(657,003)		(657,003)
Proceeds from issuance of shares of common stock as a result of stock purchased under the Employee Stock Purchase Plan	4,582	170,061			174,643
Proceeds from issuance of common stock, stock options exercised	8,027	109,392			117,419
Stock compensation expense		168,314			168,314
Restricted stock awards - common stock	2,000	(2,000)
Exchange of common stock in connection with stock options exercised and restricted stock vested	(594)	(26,730)			(27,324)
Balance at Jun. 30, 2017	$ 13,175,234	$ 158,001,006	$ 135,254,306	$ (1,347,111)	$ 305,083,435