Note 13 - Income Taxes - A Reconciliation of Income Tax Expense (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Computed at statutory rate	21.00%	35.00%	34.00%
State financial institution tax and credits	(1.30%)	(10.20%)	(4.20%)
Cash surrender value of life insurance	(1.10%)	(2.10%)	(2.20%)
Tax exempt interest	(1.40%)	(3.00%)	(3.30%)
Non-dedecutible merger costs	1.00%
Impact of 2017 Tax Act		13.10%
Other	2.00%	1.50%	2.20%
Actual effective rate	20.20%	33.30%	26.50%