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INVESTMENT SECURITIES - Additional Information (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2024 | Jun. 30, 2024 | Mar. 31, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023
Investment Securities Pledged as Collateral |  |  |  |  |  |
Accrued interest and fees receivable | $ 3,700 |  |  | $ 3,700 |  |
Investment securities pledged to collateralize certain deposits and borrowings | 2,460,000 |  |  | 2,460,000 |  | $ 2,140,000
Proceeds from sales of securities |  |  |  | $ 57,539 | $ 733,789 |
Percentage of first half of subscription on FRB stock |  |  |  | 0.50% |  |
Percentage of remaining half of subscription on FRB stock |  |  |  | 0.50% |  |
U.S. Treasury and agency securities |  |  |  |  |  |
Investment Securities Pledged as Collateral |  |  |  |  |  |
Book value of available-for-sale |  |  | $ 786,100 |  |  |
Gross realized losses |  |  | 52,300 |  |  |
Proceeds from sales of securities |  |  | $ 733,800 |  |  |
U.S. Treasury and agency securities | Securities Sold under Agreements to Repurchase |  |  |  |  |  |
Investment Securities Pledged as Collateral |  |  |  |  |  |
Investment securities pledged to collateralize certain deposits and borrowings | 393,100 |  |  | $ 393,100 |  | $ 598,900
Obligations of state and political subdivisions |  |  |  |  |  |
Investment Securities Pledged as Collateral |  |  |  |  |  |
Book value of available-for-sale | 26,800 | $ 31,200 |  | $ 26,800 |  |
Gross realized gains |  | 200 |  |  |  |
Gross realized losses | 300 | 400 |  |  |  |
Proceeds from sales of securities | $ 26,500 | $ 31,000 |  |  |  |

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