Note 10 - Income Taxes - Reconciliation of Expected Income Tax Expense With Reported Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Computed “expected” income tax expense	$ 7,135	$ 6,613	$ 7,201
Tax impact of enacted change in tax rate	1,560
Tax-exempt interest income	(2,144)	(2,234)	(2,381)
Nondeductible interest expense	89	92	101
Other, net	(347)	(519)	(181)
Total income tax expense	$ 6,293	$ 3,952	$ 4,740