Note 3 - Available for Sale Debt Securities - Securities With Unrealized Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Securities available-for-sale, less than 12 months, fair value	$ 559,939	$ 78,437
Securities available-for-sale, less than 12 months, unrealized losses	(6,325)	(279)
Securities available-for-sale, 12 months or more, fair value	2,405	25,319
Securities available-for-sale, 12 months or more, unrealized losses	(46)	(250)
Securities available-for-sale, fair value	562,344	103,756
Securities available-for-sale, unrealized losses	(6,371)	(529)
US Treasury Securities and US Government Agencies Debt Securities [Member]
Securities available-for-sale, less than 12 months, fair value	9,077
Securities available-for-sale, less than 12 months, unrealized losses	(1)
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	9,077
Securities available-for-sale, unrealized losses	(1)
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale, less than 12 months, fair value	26,808	10,404
Securities available-for-sale, less than 12 months, unrealized losses	(111)	(112)
Securities available-for-sale, 12 months or more, fair value	459	24,398
Securities available-for-sale, 12 months or more, unrealized losses	(13)	(249)
Securities available-for-sale, fair value	27,267	34,802
Securities available-for-sale, unrealized losses	(124)	(361)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale, less than 12 months, fair value	504,709	68,033
Securities available-for-sale, less than 12 months, unrealized losses	(6,085)	(167)
Securities available-for-sale, 12 months or more, fair value	1,946	921
Securities available-for-sale, 12 months or more, unrealized losses	(33)	(1)
Securities available-for-sale, fair value	506,655	68,954
Securities available-for-sale, unrealized losses	(6,118)	$ (168)
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, less than 12 months, fair value	19,345
Securities available-for-sale, less than 12 months, unrealized losses	(128)
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	19,345
Securities available-for-sale, unrealized losses	$ (128)

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of accumulated unrealized loss on 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 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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