Note 4 - Securities - Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Amortized cost, Due in one year or less, available for sale securities	$ 4,160
Fair value, Due in one year or less, available for sale securities	4,169
Amortized cost, Due after one year through five years, available for sale securities	204,152
Fair value, Due after one year through five years, available for sale securities	201,752
Amortized cost, Due after five years through ten years, available for sale securties	75,541
Fair value, Due after five years through ten years, available for sale securities	73,852
Amortized cost, Due after ten years, available for sale securities	24,199
Fair value, Due after ten years, available for sale securities	24,423
Amortized cost, No maturity, available for sale securities	189
Fair value, No maturity, available for sale securities	180
Amortized cost, Total securities available for sale	308,241
Securities available for sale	304,376	$ 304,282
Amortized cost, Due in one year or less, held to maturity securities	7,620
Fair value, Due in one year or less, held to maturity securities	7,778
Amortized cost, Due after one year through five years, held to maturity securities	26,018
Fair value, Due after one year through five years, held to maturity securities	27,490
Amortized cost, Due after five years through ten years, held to maturity securities	20,849
Fair value, Due after give years through ten years, held to maturity securities	21,558
Amortized cost, Due after ten years, held to maturity securities	79,109
Fair value, Due after ten years, held to maturity securities	80,308
Securities held to maturity (fair value of $137,134 at March 31, 2017 and $137,692 at December 31, 2016)	133,596	134,957
Securities held to maturity, fair value	$ 137,134	$ 137,692