Note 4 - Securities - Securities Held-to-maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Securities held-to-maturity, Amortized Costs	$ 133,596	$ 134,957
Securities held-to-maturity, Gross Unrealized Gains	4,096	3,817
Securities held-to-maturity, Gross Unrealized Losses	558	1,082
Securities held-to-maturity, Fair Values	137,134	137,692
US Government Agencies Debt Securities [Member]
Securities held-to-maturity, Amortized Costs	3,934	3,934
Securities held-to-maturity, Gross Unrealized Gains	220	201
Securities held-to-maturity, Gross Unrealized Losses	0	0
Securities held-to-maturity, Fair Values	4,154	4,135
US States and Political Subdivisions Debt Securities [Member]
Securities held-to-maturity, Amortized Costs	128,437	129,783
Securities held-to-maturity, Gross Unrealized Gains	3,834	3,579
Securities held-to-maturity, Gross Unrealized Losses	558	1,082
Securities held-to-maturity, Fair Values	131,713	132,280
Collateralized Mortgage Backed Securities [Member]
Securities held-to-maturity, Amortized Costs	248	265
Securities held-to-maturity, Gross Unrealized Gains	28	30
Securities held-to-maturity, Gross Unrealized Losses	0	0
Securities held-to-maturity, Fair Values	276	295
Corporate Debt Securities [Member]
Securities held-to-maturity, Amortized Costs	977	975
Securities held-to-maturity, Gross Unrealized Gains	14	7
Securities held-to-maturity, Gross Unrealized Losses	0	0
Securities held-to-maturity, Fair Values	$ 991	$ 982