Note 20 - Parent Company Only Financial Statements - Condensed Balance Sheets (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash and due from banks	$ 75,721,663	$ 70,569,993
Interest-bearing deposits at financial institutions	55,765,012	63,948,925
Securities available for sale, at fair value	272,907,907	251,113,139
Loans/leases receivable, held for investment	2,963,840,399	2,404,351,485
Premises and equipment, net	62,838,255	60,643,508
Other assets	45,817,687	37,503,284
Total assets	3,982,664,773	3,301,943,748	$ 2,593,198,275
Other borrowings	66,000,000	80,000,000
Other liabilities	53,242,979	55,690,087
Total liabilities	3,629,377,644	3,015,902,949
Common stock	13,918,168	13,106,845
Additional paid-in capital	189,077,550	156,776,642
Retained earnings	151,962,661	118,616,901
Total stockholders' equity	353,287,129	286,040,799	$ 225,885,750	$ 144,078,509
Total liabilities and stockholders' equity	3,982,664,773	3,301,943,748
Parent Company [Member]
Cash and due from banks	4,325,582	6,929,755
Interest-bearing deposits at financial institutions	601	651
Securities available for sale, at fair value	1,690,726	1,545,565
Loans/leases receivable, held for investment	1,710,000
Premises and equipment, net	4,947,572	5,104,677
Other assets	11,630,304	15,245,521
Total assets	437,366,647	375,847,099
Other borrowings	31,000,000	35,000,000
Junior subordinated debentures	37,486,487	33,480,202
Other liabilities	15,593,031	21,326,098
Total liabilities	84,079,518	89,806,300
Common stock	13,918,168	13,106,845
Additional paid-in capital	189,077,550	156,776,642
Retained earnings	151,962,661	118,616,901
Accumulated other comprehensive loss	(1,671,250)	(2,459,589)
Total stockholders' equity	353,287,129	286,040,799
Total liabilities and stockholders' equity	437,366,647	375,847,099
Parent Company [Member] | Bank Subsidiaries [Member]
Investment in bank subsidiaries	410,105,525	345,866,288
Parent Company [Member] | Non-bank Subsidiaries [Member]
Investment in bank subsidiaries	$ 2,956,337	$ 1,154,642