Note 12 - Income Taxes - Reconciliation of Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statutory federal income tax rate	21.00%	21.00%
Federal tax-exempt income	(7.00%)	(6.50%)
State income taxes, net of federal income tax benefit	4.40%	4.70%
Nondeductible expenses	0.10%	0.10%
Other	0.10%	(0.30%)
	18.60%	19.00%