Note 4 - Securities - Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Amortized cost, due in one year or less, available for sale securities	$ 11,256
Fair value, due in one year or less, available for sale securities	11,231
Amortized cost, due after one year through five years, available for sale securities	211,312
Fair value, due after one year through five years, available for sale securities	209,270
Amortized cost, due after five years through ten years, available for sale securties	61,843
Fair value, due after five years through ten years, available for sale securities	61,033
Amortized cost, due after ten years, available for sale securities	26,907
Fair value, due after ten years, available for sale securities	27,789
Amortized cost, total securities available for sale	311,318
Fair value, total securities available for sale	309,323	$ 304,282
Amortized cost, due in one year or less, held to maturity securities	11,646
Fair value, due in one year or less, held to maturity securities	11,907
Amortized cost, due after one year through five years, held to maturity securities	25,962
Fair value, due after one year through five years, held to maturity securities	27,339
Amortized cost, due after five years through ten years, held to maturity securities	23,388
Fair value, due after give years through ten years, held to maturity securities	24,207
Amortized cost, due after ten years, held to maturity securities	68,754
Fair value, due after ten years, held to maturity securities	70,406
Amortized cost, total securities held to maturity	129,750	134,957
Fair value, total securities held to maturity	$ 133,859	$ 137,692