Note 2 - Available for Sale Debt Securities - Securities With Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Securities available-for-sale, less than 12 months, fair value	$ 391,274	$ 78,437
Securities available-for-sale, less than 12 months, unrealized losses	(10,106)	(279)
Securities available-for-sale, 12 months or more, fair value	24,592	25,319
Securities available-for-sale, 12 months or more, unrealized losses	(253)	(250)
Securities available-for-sale, fair value	415,866	103,756
Securities available-for-sale, unrealized losses	(10,359)	(529)
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale, less than 12 months, fair value	10,309	10,404
Securities available-for-sale, less than 12 months, unrealized losses	(96)	(112)
Securities available-for-sale, 12 months or more, fair value	23,829	24,398
Securities available-for-sale, 12 months or more, unrealized losses	(252)	(249)
Securities available-for-sale, fair value	34,138	34,802
Securities available-for-sale, unrealized losses	(348)	(361)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale, less than 12 months, fair value	369,126	68,033
Securities available-for-sale, less than 12 months, unrealized losses	(9,594)	(167)
Securities available-for-sale, 12 months or more, fair value	763	921
Securities available-for-sale, 12 months or more, unrealized losses	(1)	(1)
Securities available-for-sale, fair value	369,889	68,954
Securities available-for-sale, unrealized losses	(9,595)	$ (168)
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, less than 12 months, fair value	11,839
Securities available-for-sale, less than 12 months, unrealized losses	(416)
Securities available-for-sale, 12 months or more, fair value	0
Securities available-for-sale, 12 months or more, unrealized losses	0
Securities available-for-sale, fair value	11,839
Securities available-for-sale, unrealized losses	$ (416)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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