Note 20 - Parent Company Only Financial Statements - Condensed Statements of Cash Flows (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income (loss)	$ 9,901,590	$ 7,853,935	$ 8,766,017	$ 9,184,965	$ 8,529,330	$ 6,107,501	$ 6,676,467	$ 6,373,489	$ 35,706,507	$ 27,686,787	$ 16,927,881
Stock-based compensation expense									1,187,036	947,174	941,469
Securities gains, net									87,885	(4,592,398)	(798,983)
Net decrease (increase) in interest-bearing deposits at financial institutions									12,137,820	(12,904,803)	(979,283)
Calls, maturities and redemptions									43,010,478	117,876,284	211,942,737
Sales									71,091,580	134,188,737	81,410,368
Purchase of premises and equipment									(5,760,802)	(6,032,416)	(4,394,255)
Net cash (used in) provided by investing activities									(410,516,757)	(168,975,229)	(66,073,152)
Proceeds from other borrowings									7,000,000	35,000,000
Calls, maturities and scheduled principal payments									(21,000,000)		(7,350,000)
Prepayments										(69,769,000)	(34,559,000)
Retirement of junior subordinated debentures										(3,955,000)	(1,762,000)
Net proceeds from the common stock offering							$ 29,800,000
Net cash provided by financing activities									381,955,146	154,420,080	39,481,832
Net increase (decrease) in cash and due from banks									5,151,670	28,827,672	3,507,302
Cash and due from banks, beginning				70,569,993				41,742,321	70,569,993	41,742,321	38,235,019
Cash and due from banks, ending	75,721,663				70,569,993				75,721,663	70,569,993	41,742,321
Common Stock Offering 1 [Member]
Net proceeds from the common stock offering										29,828,916	63,484,123
Common Stock Offering 2 [Member]
Net proceeds from the common stock offering									2,055,507	2,105,774	1,552,673
Parent Company [Member]
Net income (loss)									35,706,507	27,686,787	16,927,881
Accretion of acquisition fair value adjustments									149,010	136,150	137,317
Depreciation									225,947	222,256	174,757
Stock-based compensation expense									1,187,036	947,174	941,469
Securities gains, net									(6,312)	(37,596)	(262,801)
Gains on debt extinguishment										(1,200,000)	(300,000)
Decrease (increase) in other assets									(968,808)	(2,346,253)	(5,929,110)
(Decrease) increase in other liabilities									(6,918,921)	5,105,251	5,502,390
Net cash provided by operating activities									5,234,256	23,046,243	4,832,689
Net decrease (increase) in interest-bearing deposits at financial institutions									50	50	189,426
Purchases										(3,873,060)	(1,764,137)
Calls, maturities and redemptions									6,312	3,800,000	1,772,719
Sales									31,713	132,738	489,828
Capital infusion, bank subsidiaries											(45,600,000)
Net cash paid for acquisitions									(3,368,909)	(80,000,000)
Purchase of premises and equipment									(68,842)	(824,498)	(1,517,157)
Net cash (used in) provided by investing activities									(3,399,676)	(80,764,770)	(46,429,321)
Proceeds from other borrowings									7,000,000	35,000,000
Calls, maturities and scheduled principal payments									(11,000,000)		(2,350,000)
Prepayments											(19,395,116)
Retirement of junior subordinated debentures										(3,955,000)	(1,762,000)
Payment of cash dividends on common and preferred stock									(2,494,260)	(1,981,541)	(782,054)
Net proceeds from the common stock offering									2,055,507	2,105,774	1,552,673
Net cash provided by financing activities									(4,438,753)	60,998,149	40,747,626
Net increase (decrease) in cash and due from banks									(2,604,173)	3,279,622	(849,006)
Cash and due from banks, beginning				$ 6,929,755				$ 3,650,133	6,929,755	3,650,133	4,499,139
Cash and due from banks, ending	$ 4,325,582				$ 6,929,755				4,325,582	6,929,755	3,650,133
Parent Company [Member] | Common Stock Offering 1 [Member]
Net proceeds from the common stock offering											63,484,123
Parent Company [Member] | Common Stock Offering 2 [Member]
Net proceeds from the common stock offering										29,828,916
Parent Company [Member] | Bank Subsidiaries [Member]
Earnings of bank subsidiaries									(45,103,593)	(33,467,712)	(22,059,086)
Distributions from bank subsidiaries									21,000,000	26,000,000	9,700,000
Parent Company [Member] | Non-bank Subsidiaries [Member]
Earnings of bank subsidiaries									(75,344)	(32,674)	(32,823)
Distributions from bank subsidiaries									$ 38,734	$ 32,860	$ 32,695