Note 4 - Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Securities available-for-sale, amortized costs	$ 393,237	$ 431,428
Securities available-for-sale, gross unrealized gains	3,925	1,709
Securities available-for-sale, gross unrealized losses	815	8,127
Securities available-for-sale, fair values	396,347	425,010
US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized costs	287,696	306,264
Securities available-for-sale, gross unrealized gains	1,990	449
Securities available-for-sale, gross unrealized losses	749	6,666
Securities available-for-sale, fair values	288,937	300,047
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized costs	101,028	118,564
Securities available-for-sale, gross unrealized gains	1,840	1,218
Securities available-for-sale, gross unrealized losses	65	1,166
Securities available-for-sale, fair values	102,803	118,616
Collateralized Mortgage Backed Securities [Member]
Securities available-for-sale, amortized costs	519	586
Securities available-for-sale, gross unrealized gains	51	42
Securities available-for-sale, gross unrealized losses	0	0
Securities available-for-sale, fair values	570	628
Corporate Debt Securities [Member]
Securities available-for-sale, amortized costs	3,994	6,014
Securities available-for-sale, gross unrealized gains	44
Securities available-for-sale, gross unrealized losses	1	295
Securities available-for-sale, fair values	$ 4,037	$ 5,719

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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