Note 14 - Income Taxes - A Reconciliation of Income Tax Expense (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Computed at statutory rate	21.00%	21.00%	34.00%
State financial institution tax and credits	(2.30%)	(1.30%)	(10.20%)
Cash surrender value of life insurance	(1.00%)	(1.10%)	(2.10%)
Tax exempt interest	(1.10%)	(1.40%)	(3.00%)
Non-dedecutible merger costs		1.00%
Impact of 2017 Tax Act			13.10%
Other	(1.40%)	2.00%	1.50%
Actual effective rate	15.20%	20.20%	33.30%