Note 14 - Income Taxes - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Federal income tax, at statutory rate	21.00%	21.00%	34.00%
State franchise tax, net of Federal tax effect	7.60%	7.40%	6.20%
Interest on obligations of states and political subdivisions	(0.90%)	(0.90%)	(1.50%)
Net increase in cash surrender value of bank owned life insurance	(0.30%)	(0.40%)	(0.70%)
Deferred tax Federal rate adjustment			9.20%
Other		(0.30%)
Effective tax rate	27.40%	26.80%	47.20%