Note 4 - Securities - Expected Maturities of Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available-for-sale securities, amortized cost, one year or less	$ 1,426
Available-for-sale securities, fair value, one year or less	1,430
Held-to-maturity securities, amortized cost, one year or less
Held-to-maturity securities, fair value, one year or less
Available-for-sale securities, amortized cost, after one year through five years	58,755
Available-for-sale securities, fair value, after one year through five years	58,692
Held-to-maturity securities, amortized cost, after one year through five years	6,750
Held-to-maturity securities, fair value, after one year through five years	7,048
Available-for-sale securities, amortized cost, after five years through ten years	72,341
Available-for-sale securities, fair value, after five years through ten years	72,954
Held-to-maturity securities, amortized cost, after five years through ten years	11,448
Held-to-maturity securities, fair value, after five years through ten years	11,889
Available-for-sale securities, amortized cost, after ten years	76,405
Available-for-sale securities, fair value, after ten years	76,533
Held-to-maturity securities, amortized cost, after ten years	13,131
Held-to-maturity securities, fair value, after ten years	13,612
Available-for-sale securities, amortized cost, total	208,927
Available-for-sale securities, fair value, total	209,609	$ 175,174
Held-to-maturity securities, amortized cost, total	31,329	$ 31,187
Held-to-maturity securities, fair value, total	$ 32,549