Note 13 - Income Taxes - A Reconciliation of Income Tax Expense (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Computed at statutory rate	21.00%	21.00%	21.00%
State financial institution tax and credits	1.10%	1.20%	2.30%
State financial institution tax and credits	(1.10%)	(1.20%)	(2.30%)
Cash surrender value of life insurance	(1.00%)	(1.60%)	(1.00%)
Tax exempt interest	(1.10%)	(1.80%)	(1.10%)
Other	0.10%	(1.10%)	(1.40%)
Actual effective rate	20.10%	15.30%	15.20%