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Note 3 - Investment Securities - Credit Quality (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Held to Maturity, Amortized Cost	$ 839,349	$ 844,635
AAA/AA/A [Member]
Held to Maturity, Amortized Cost	656,610
BBB+/BBB [Member]
Held to Maturity, Amortized Cost	182,275
NR [Member]
Held to Maturity, Amortized Cost	464
Agency Residential MBS [Member]
Held to Maturity, Amortized Cost	53,528	57,927
Agency Residential MBS [Member] | AAA/AA/A [Member]
Held to Maturity, Amortized Cost	53,064
Agency Residential MBS [Member] | BBB+/BBB [Member]
Held to Maturity, Amortized Cost	0
Agency Residential MBS [Member] | NR [Member]
Held to Maturity, Amortized Cost	464
US States and Political Subdivisions Debt Securities [Member]
Held to Maturity, Amortized Cost	48,675	51,261
US States and Political Subdivisions Debt Securities [Member] | AAA/AA/A [Member]
Held to Maturity, Amortized Cost	48,675
US States and Political Subdivisions Debt Securities [Member] | BBB+/BBB [Member]
Held to Maturity, Amortized Cost	0
US States and Political Subdivisions Debt Securities [Member] | NR [Member]
Held to Maturity, Amortized Cost	0
Corporate Debt Securities [Member]
Held to Maturity, Amortized Cost	737,146	$ 735,447
Corporate Debt Securities [Member] | AAA/AA/A [Member]
Held to Maturity, Amortized Cost	554,871
Corporate Debt Securities [Member] | BBB+/BBB [Member]
Held to Maturity, Amortized Cost	182,275
Corporate Debt Securities [Member] | NR [Member]
Held to Maturity, Amortized Cost	$ 0

X

- Definition

Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-14

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