Note 6 - Available-for-Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	$ 444,616	$ 349,710
Investment securities available-for-sale, debt securities gross unrealized holding gains	7,207	1,602
Investment securities available-for-sale, debt securities gross unrealized holding losses	(454)	(1,277)
Investment securities available-for-sale, debt securities amortized cost	437,863	349,385
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	81,533	69,298
Investment securities available-for-sale, debt securities gross unrealized holding gains	82	8
Investment securities available-for-sale, debt securities gross unrealized holding losses	(152)	(213)
Investment securities available-for-sale, debt securities amortized cost	81,603	69,503
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	77,016	50,781
Investment securities available-for-sale, debt securities gross unrealized holding gains	1,824	860
Investment securities available-for-sale, debt securities gross unrealized holding losses	(140)	(19)
Investment securities available-for-sale, debt securities amortized cost	75,332	49,940
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	176,982	134,829
Investment securities available-for-sale, debt securities gross unrealized holding gains	3,232	371
Investment securities available-for-sale, debt securities gross unrealized holding losses	(112)	(504)
Investment securities available-for-sale, debt securities amortized cost	173,862	134,962
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	101,843	86,610
Investment securities available-for-sale, debt securities gross unrealized holding gains	2,043	260
Investment securities available-for-sale, debt securities gross unrealized holding losses	(9)	(535)
Investment securities available-for-sale, debt securities amortized cost	99,809	86,885
Collateralized Debt Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	68	79
Investment securities available-for-sale, debt securities gross unrealized holding losses	(16)	(6)
Investment securities available-for-sale, debt securities amortized cost	84	85
Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	7,174	8,113
Investment securities available-for-sale, debt securities gross unrealized holding gains	26	103
Investment securities available-for-sale, debt securities gross unrealized holding losses	(25)
Investment securities available-for-sale, debt securities amortized cost	$ 7,173	$ 8,010

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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