Note 4 - Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Securities available-for-sale, amortized costs	$ 472,460	$ 435,166
Securities available-for-sale, gross unrealized gains	15,330	2,951
Securities available-for-sale, gross unrealized losses	439	2,854
Securities available-for-sale, fair values	487,351	435,263
US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized costs	57,906	119,903
Securities available-for-sale, gross unrealized gains	4,712	1,995
Securities available-for-sale, gross unrealized losses	25	775
Securities available-for-sale, fair values	62,593	121,123
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized costs	157,528	88,092
Securities available-for-sale, gross unrealized gains	5,936	791
Securities available-for-sale, gross unrealized losses	350	644
Securities available-for-sale, fair values	163,114	88,239
Collateralized Mortgage Backed Securities [Member]
Securities available-for-sale, amortized costs	254,025	223,173
Securities available-for-sale, gross unrealized gains	4,363	45
Securities available-for-sale, gross unrealized losses	64	1,435
Securities available-for-sale, fair values	258,324	221,783
Corporate Debt Securities [Member]
Securities available-for-sale, amortized costs	3,001	3,998
Securities available-for-sale, gross unrealized gains	319	120
Securities available-for-sale, fair values	$ 3,320	$ 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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Amount, before tax, of unrealized loss 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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