Note 10 - Commitments and Contingent Liabilities - Unused and Available Credit Balances of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financial instruments	$ 212,091	$ 180,838
Financial Standby Letter of Credit [Member]
Financial instruments	36,221	55,105
Performance Guarantee [Member]
Financial instruments	3,256	4,339
Construction Mortgages [Member]
Financial instruments	55,001	30,619
Personal Line Of Credit [Member]
Financial instruments	6,378	6,183
Overdraft Protection Lines [Member]
Financial instruments	6,140	6,167
Home Equity Lines of Credit [Member]
Financial instruments	21,191	16,337
Commercial Lines Of Credit [Member]
Financial instruments	$ 83,904	$ 62,088