Note 13 - Federal and State Income Taxes - Reconciliation of the Expected Federal Income Tax Expense (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Computed "expected" tax expense									$ 10,948,310	$ 14,228,535	$ 12,806,351
Effect of graduated tax rates											(250,013)
Tax exempt income, net									(3,957,851)	(5,653,979)	(4,343,270)
Bank-owned life insurance									(342,667)	(630,855)	(619,988)
State income taxes, net of federal benefit, current year									2,680,581	1,764,671	1,245,524
Change in unrecognized tax benefits									(44,629)	(53,699)	121,008
New Markets Tax Credit amd other credits									154,200	341,268	180,000
Acquisition costs									226,599		176,050
Excess tax benefit on stock options exercised and restricted stock awards vested									(425,142)	(1,219,483)
Re-measurement of deferred tax asset to incorporate newly enacted tax rates										(2,918,606)
Other									84,111	(228,866)	(52,875)
Federal and state income tax expense	$ 3,535,188	$ 1,608,035	$ 1,880,819	$ 1,991,070	$ (2,000,105)	$ 1,921,533	$ 2,635,576	$ 2,389,446	$ 9,015,112	$ 4,946,450	$ 8,902,787
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent									21.00%	35.00%	35.00%
Effect of graduated tax rates, percentage											(0.70%)
Tax exempt income, net, percentage									(7.60%)	(13.90%)	(11.90%)
Bank-owned life insurance, percentage									(0.60%)	(1.50%)	(1.70%)
State income taxes, net of federal benefit, current year, percentage									5.20%	4.30%	3.40%
Change in unrecognized tax benefits, percentage									(0.10%)	(0.10%)	0.30%
New Markets Tax Credits and other credits, percentage									0.30%	0.80%	0.50%
Acquisition costs, percentage									0.40%		0.50%
Excess tax benefit on stock options exercised and restricted stock awards vested, Percentage									(0.80%)	(3.00%)
Re-measurement of deferred tax asset to incorporate newly enacted tax rates, percentage										(7.20%)
Other, percentage									0.10%	(0.60%)	(0.10%)
Effective Income Tax Rate Reconciliation, Percent, Total									17.30%	12.20%	24.30%