Note 14 - Income Taxes - Reconciliation of Income Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Expected provision	$ 7,388	$ 7,633	$ 7,972
Expected provision, percentage	35.00%	35.00%	35.00%
Tax-exempt interest income	$ (1,801)	$ (1,914)	$ (1,982)
Tax-exempt interest income, percentage	(8.53%)	(8.78%)	(8.70%)
Nondeductible interest expense	$ 40	$ 51	$ 56
Nondeductible interest expense, percentage	0.19%	0.23%	0.25%
Dividends received deduction	$ (22)	$ (75)	$ (79)
Dividends received deduction, percentage	(0.10%)	(0.34%)	(0.35%)
Increase in cash surrender value of life insurance	$ (134)	$ (135)	$ (132)
Increase in cash surrender value of life insurance, percentage	(0.63%)	(0.62%)	(0.58%)
Employee stock option compensation	$ 0	$ 0	$ 41
Employee stock option compensation, percentage	0.00%	0.00%	0.18%
Tax benefit from limited partnership investment	$ (76)	$ (80)	$ (83)
Tax benefit from limited partnership investment, percentage	(0.36%)	(0.37%)	(0.36%)
Other, net	$ (48)	$ (143)	$ (101)
Other, net, percentage	(0.23%)	(0.66%)	(0.44%)
Effective income tax provision	$ 5,347	$ 5,337	$ 5,692
Effective income tax provision, percentage	25.33%	24.47%	24.99%