Note 4 - Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Securities available-for-sale, amortized costs	$ 434,044	$ 435,166
Securities available-for-sale, gross unrealized gains	9,502	2,951
Securities available-for-sale, gross unrealized losses	4,527	2,854
Securities available-for-sale, fair values	439,019	435,263
US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized costs	96,752	119,903
Securities available-for-sale, gross unrealized gains	4,879	1,995
Securities available-for-sale, gross unrealized losses	24	775
Securities available-for-sale, fair values	101,607	121,123
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized costs	100,811	88,092
Securities available-for-sale, gross unrealized gains	2,028	791
Securities available-for-sale, gross unrealized losses	542	644
Securities available-for-sale, fair values	102,297	88,239
Collateralized Mortgage Backed Securities [Member]
Securities available-for-sale, amortized costs	232,481	223,173
Securities available-for-sale, gross unrealized gains	2,469	45
Securities available-for-sale, gross unrealized losses	3,961	1,435
Securities available-for-sale, fair values	230,989	221,783
Corporate Debt Securities [Member]
Securities available-for-sale, amortized costs	4,000	3,998
Securities available-for-sale, gross unrealized gains	126	120
Securities available-for-sale, gross unrealized losses
Securities available-for-sale, fair values	$ 4,126	$ 4,118

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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