Note 4 - Debt Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	$ 435,646	$ 349,710
Investment securities available-for-sale, debt securities gross unrealized holding gains	7,514	1,602
Investment securities available-for-sale, debt securities gross unrealized holding losses	(363)	(1,277)
Investment securities available-for-sale, debt securities amortized cost	428,495	349,385
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	69,776	69,298
Investment securities available-for-sale, debt securities gross unrealized holding gains	26	8
Investment securities available-for-sale, debt securities gross unrealized holding losses	(246)	(213)
Investment securities available-for-sale, debt securities amortized cost	69,996	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	87,812	50,781
Investment securities available-for-sale, debt securities gross unrealized holding gains	2,350	860
Investment securities available-for-sale, debt securities gross unrealized holding losses	(45)	(19)
Investment securities available-for-sale, debt securities amortized cost	85,507	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	175,847	134,829
Investment securities available-for-sale, debt securities gross unrealized holding gains	3,328	371
Investment securities available-for-sale, debt securities gross unrealized holding losses	(24)	(504)
Investment securities available-for-sale, debt securities amortized cost	172,543	134,962
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	94,948	86,610
Investment securities available-for-sale, debt securities gross unrealized holding gains	1,751	260
Investment securities available-for-sale, debt securities gross unrealized holding losses	(5)	(535)
Investment securities available-for-sale, debt securities amortized cost	93,202	86,885
Collateralized Debt Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	70	79
Investment securities available-for-sale, debt securities gross unrealized holding losses	(14)	(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	7,193	8,113
Investment securities available-for-sale, debt securities gross unrealized holding gains	59	103
Investment securities available-for-sale, debt securities gross unrealized holding losses	(29)
Investment securities available-for-sale, debt securities amortized cost	$ 7,163	$ 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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