Note 3 - Securities - Expected Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale securities, amortized cost, one year or less	$ 1,379
Available-for-sale securities, fair value, one year or less	1,382
Held-to-maturity securities, amortized cost, one year or less	95
Held-to-maturity securities, fair value, one year or less	98
Available-for-sale securities, amortized cost, after one year through five years	75,268
Available-for-sale securities, fair value, after one year through five years	75,183
Held-to-maturity securities, amortized cost, after one year through five years	9,834
Held-to-maturity securities, fair value, after one year through five years	10,354
Available-for-sale securities, amortized cost, after five years through ten years	72,459
Available-for-sale securities, fair value, after five years through ten years	72,951
Held-to-maturity securities, amortized cost, after five years through ten years	7,656
Held-to-maturity securities, fair value, after five years through ten years	7,838
Available-for-sale securities, amortized cost, after ten years	82,758
Available-for-sale securities, fair value, after ten years	82,978
Held-to-maturity securities, amortized cost, after ten years	13,139
Held-to-maturity securities, fair value, after ten years	13,592
Available-for-sale securities, amortized cost, total	231,864
Available-for-sale securities, fair value, total	232,494	$ 175,174
Held-to-maturity securities, amortized cost, total	30,724	$ 31,187
Held-to-maturity securities, fair value, total	$ 31,882