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Note 9 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands | Jun. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Debt securities available for sale |  | $ 3,226,449 |  | $ 3,395,810 |
Agency Residential MBS [Member] |  |  |  |  |
Debt securities available for sale |  | 195,278 |  | 211,060 |
Agency Commercial MBS [Member] |  |  |  |  |
Debt securities available for sale |  | 96,265 |  | 6,966 |
US Government Agencies Debt Securities [Member] |  |  |  |  |
Debt securities available for sale |  | 301,903 |  | 292,117 |
US Treasury Securities [Member] |  |  |  |  |
Debt securities available for sale |  |  |  | 4,955 |
US States and Political Subdivisions Debt Securities [Member] |  |  |  |  |
Debt securities available for sale |  | 60,835 |  | 62,186 |
Corporate Debt Securities [Member] |  |  |  |  |
Debt securities available for sale |  | 1,792,021 |  | 1,835,937 |
Fair Value, Recurring [Member] |  |  |  |  |
Debt securities available for sale |  | 3,226,449 |  | 3,395,810 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 |  | 4,955 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Debt securities available for sale |  | 3,226,449 |  | 3,390,855 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 | [1] | 0 | [2]
Fair Value, Recurring [Member] | Agency Residential MBS [Member] |  |  |  |  |
Debt securities available for sale |  | 195,278 |  | 211,060 |
Fair Value, Recurring [Member] | Agency Residential MBS [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 |  | 0 |
Fair Value, Recurring [Member] | Agency Residential MBS [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Debt securities available for sale |  | 195,278 |  | 211,060 |
Fair Value, Recurring [Member] | Agency Residential MBS [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 | [1] | 0 | [2]
Fair Value, Recurring [Member] | Agency Commercial MBS [Member] |  |  |  |  |
Debt securities available for sale |  | 96,265 |  | 6,966 |
Fair Value, Recurring [Member] | Agency Commercial MBS [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 |  | 0 |
Fair Value, Recurring [Member] | Agency Commercial MBS [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Debt securities available for sale |  | 96,265 |  | 6,966 |
Fair Value, Recurring [Member] | Agency Commercial MBS [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 | [1] | 0 | [2]
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] |  |  |  |  |
Debt securities available for sale |  | 301,903 |  | 292,117 |
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 |  | 0 |
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Debt securities available for sale |  | 301,903 |  | 292,117 |
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 | [1] | 0 | [2]
Fair Value, Recurring [Member] | US Treasury Securities [Member] |  |  |  |  |
Debt securities available for sale |  |  |  | 4,955 |
Fair Value, Recurring [Member] | US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Debt securities available for sale |  |  |  | 4,955 |
Fair Value, Recurring [Member] | US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Debt securities available for sale |  |  |  | 0 |
Fair Value, Recurring [Member] | US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Debt securities available for sale | [2] |  |  | 0 |
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] |  |  |  |  |
Debt securities available for sale |  | 60,835 |  | 62,186 |
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 |  | 0 |
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Debt securities available for sale |  | 60,835 |  | 62,186 |
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 | [1] | 0 | [2]
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] |  |  |  |  |
Debt securities available for sale |  | 1,792,021 |  | 1,835,937 |
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 |  | 0 |
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Debt securities available for sale |  | 1,792,021 |  | 1,835,937 |
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 | [1] | 0 | [2]
Fair Value, Recurring [Member] | Collateralized Loan Obligations [Member] |  |  |  |  |
Debt securities available for sale |  | 780,147 |  | 982,589 |
Fair Value, Recurring [Member] | Collateralized Loan Obligations [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Debt securities available for sale |  | 0 |  | 0 |
Fair Value, Recurring [Member] | Collateralized Loan Obligations [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Debt securities available for sale |  | 780,147 |  | 982,589 |
Fair Value, Recurring [Member] | Collateralized Loan Obligations [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Debt securities available for sale |  | $ 0 | [1] | $ 0 | [2]
[1] | There were no transfers into or out of level 3 during the six months ended June 30, 2025.
[2] | There were no transfers into or out of level 3 during the year ended December 31, 2024.

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- Definition Amount excluding accrued interest, 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/2009/role/commonPracticeRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479130/326-30-45-1 + Details
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