Note 8 - Investment Securities - Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Investment securities available for sale, amortized cost	$ 1,684,951	$ 1,622,173
Investment securities available for sale, gross unrealized gains	227	690
Investment securities available for sale, gross unrealized losses	176,380	149,515
Securities available-for-sale	1,508,798	1,473,348
US Treasury Securities [Member]
Investment securities available for sale, amortized cost	392,956	241,611
Investment securities available for sale, gross unrealized gains	41	0
Investment securities available for sale, gross unrealized losses	155	1,111
Securities available-for-sale	392,842	240,500
US Government Corporations and Agencies Securities [Member]
Investment securities available for sale, amortized cost	51,018	63,347
Investment securities available for sale, gross unrealized gains	144	384
Investment securities available for sale, gross unrealized losses	161	121
Securities available-for-sale	51,001	63,610
US Government-sponsored Enterprises Debt Securities [Member]
Investment securities available for sale, amortized cost	33,709	30,000
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	89	0
Securities available-for-sale	33,620	30,000
Collateralized Mortgage-Backed Securities [Member]
Investment securities available for sale, amortized cost	916,719	993,883
Investment securities available for sale, gross unrealized gains	42	194
Investment securities available for sale, gross unrealized losses	154,958	126,983
Securities available-for-sale	761,803	867,094
Collateralized Mortgage Obligations [Member]
Investment securities available for sale, amortized cost	32,015	34,552
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	4,317	3,491
Securities available-for-sale	27,698	31,061
Corporate Debt Securities [Member]
Investment securities available for sale, amortized cost	248,534	258,780
Investment securities available for sale, gross unrealized gains	0	112
Investment securities available for sale, gross unrealized losses	16,662	17,809
Securities available-for-sale	231,872	$ 241,083
Debt Security, Corporate, Non-US [Member]
Investment securities available for sale, amortized cost	10,000
Investment securities available for sale, gross unrealized gains	0
Investment securities available for sale, gross unrealized losses	38
Securities available-for-sale	$ 9,962

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).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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