Note 8 - Investment Securities - Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Investment securities available for sale, amortized cost	$ 1,629,357	$ 1,622,173
Investment securities available for sale, gross unrealized gains	245	690
Investment securities available for sale, gross unrealized losses	142,281	149,515
Securities available-for-sale	1,487,321	1,473,348
US Treasury Securities [Member]
Investment securities available for sale, amortized cost	272,485	241,611
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	447	1,111
Securities available-for-sale	272,038	240,500
US Government Corporations and Agencies Securities [Member]
Investment securities available for sale, amortized cost	55,485	63,347
Investment securities available for sale, gross unrealized gains	190	384
Investment securities available for sale, gross unrealized losses	132	121
Securities available-for-sale	55,543	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	95	0
Securities available-for-sale	33,614	30,000
Collateralized Mortgage-Backed Securities [Member]
Investment securities available for sale, amortized cost	943,270	993,883
Investment securities available for sale, gross unrealized gains	46	194
Investment securities available for sale, gross unrealized losses	121,072	126,983
Securities available-for-sale	822,244	867,094
Collateralized Mortgage Obligations [Member]
Investment securities available for sale, amortized cost	33,051	34,552
Investment securities available for sale, gross unrealized gains	0	0
Investment securities available for sale, gross unrealized losses	3,548	3,491
Securities available-for-sale	29,503	31,061
Corporate Debt Securities [Member]
Investment securities available for sale, amortized cost	268,616	258,780
Investment securities available for sale, gross unrealized gains	6	112
Investment securities available for sale, gross unrealized losses	16,694	17,809
Securities available-for-sale	251,928	$ 241,083
Debt Security, Corporate, Non-US [Member]
Investment securities available for sale, amortized cost	22,741
Investment securities available for sale, gross unrealized gains	3
Investment securities available for sale, gross unrealized losses	293
Securities available-for-sale	$ 22,451

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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Amount, before tax, of unrealized loss 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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ 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))
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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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
-Section 50
-Paragraph 2
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-Publisher FASB
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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
-Topic 942
-SubTopic 210
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-Section S99
-Paragraph 1
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-Publisher FASB
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 30
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