Note 6 - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Fair value	$ 16,843
Due after one year through five years, Fair value	285,518
Due after five years through ten years, Fair value	35,097
Due after ten years, Fair value	23,699
Total investment securities available-for-sale, Fair value	361,157	$ 344,221
Due in one year or less, Amortized cost	16,852
Due after one year through five years, Amortized cost	285,896
Due after five years through ten years, Amortized cost	34,598
Due after ten years, Amortized cost	23,126
Investment securities available-for-sale, debt securities amortized cost	$ 360,472	$ 353,249

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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