Note 4 - Debt and Equity Securities - Debt and Equity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available-for-sale, amortized cost	$ 565,109	$ 420,207
Securities, Available-for-sale, Gross Unrealized Gains	11,065	2,908
Securities, Available-for-sale, Gross Unrealized Losses	1,171	1,970
Debt Securities, Available-for-sale, Total	575,003	421,145
US Government-sponsored Enterprises Debt Securities [Member]
Available-for-sale, amortized cost	116,457	59,735
Securities, Available-for-sale, Gross Unrealized Gains	429	48
Securities, Available-for-sale, Gross Unrealized Losses	78	204
Debt Securities, Available-for-sale, Total	116,808	59,579
Collateralized Mortgage Backed Securities [Member]
Available-for-sale, amortized cost	296,845	265,648
Securities, Available-for-sale, Gross Unrealized Gains	6,877	2,300
Securities, Available-for-sale, Gross Unrealized Losses	607	635
Debt Securities, Available-for-sale, Total	303,115	267,313
Asset-backed Securities [Member]
Available-for-sale, amortized cost	26,717	27,531
Securities, Available-for-sale, Gross Unrealized Gains	495	1
Securities, Available-for-sale, Gross Unrealized Losses	133	303
Debt Securities, Available-for-sale, Total	27,079	27,229
Corporate Debt Securities [Member]
Available-for-sale, amortized cost	2,500	0
Securities, Available-for-sale, Gross Unrealized Gains	11	0
Securities, Available-for-sale, Gross Unrealized Losses	0	0
Debt Securities, Available-for-sale, Total	2,511	0
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale, amortized cost	122,590	67,293
Securities, Available-for-sale, Gross Unrealized Gains	3,253	559
Securities, Available-for-sale, Gross Unrealized Losses	353	828
Debt Securities, Available-for-sale, Total	$ 125,490	$ 67,024

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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