Note 6 - Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Fair value	$ 4,452
Due after one year through five years, Fair value	267,012
Due after five years through ten years, Fair value	52,600
Due after ten years, Fair value	20,303
Total investment securities available-for-sale, Fair value	344,367	$ 344,221
Due in one year or less, Amortized cost	4,438
Due after one year through five years, Amortized cost	271,292
Due after five years through ten years, Amortized cost	53,007
Due after ten years, Amortized cost	20,228
Investment securities available-for-sale, debt securities amortized cost	$ 348,965	$ 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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