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INVESTMENT SECURITIES - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands | Jun. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | $ 2,240,374 | $ 2,287,372
Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 185,397 |
Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 149,970 |
Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 185,019 |
Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 133,560 |
A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 131,306 |
A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 10,171 |
A3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 10,122 |
Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 1,434,829 |
State and municipal |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 1,111,355 | $ 1,117,552
State and municipal | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 114,813 |
State and municipal | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 149,970 |
State and municipal | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 185,019 |
State and municipal | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 133,560 |
State and municipal | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 131,306 |
State and municipal | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 10,171 |
State and municipal | A3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 10,122 |
State and municipal | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 376,394 |
Other |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 1,129,019 |
Other | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 70,584 |
Other | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 |
Other | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 |
Other | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 |
Other | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 |
Other | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 |
Other | A3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 |
Other | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | $ 1,058,435 |

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