Note 3 - Debt and Equity Securities - Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Due in one year or less, securities available-for-sale, amortized cost	$ 470
Due in one year or less, securities available-for-sale, estimated market value	469
Due after one year through five years, securities available-for-sale, amortized cost	12,372
Due after one year through five years, securities available-for-sale, estimated market value	12,486
Due after five years through ten years, securities available-for-sale, amortized cost	70,268
Due after five years through ten years, securities available-for-sale, estimated market value	71,430
Due after ten years, securities available-for-sale, amortized cost	317,621
Due after ten years, securities available-for-sale, estimated market value	322,839
Amortized cost	400,731	$ 420,207
Estimated market value	$ 407,224

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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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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