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INVESTMENT SECURITIES - Amortized Cost of Investment Securities Held to Maturity (Details) - USD ($) $ in Thousands | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | $ 2,263,426 | $ 2,287,372
Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 179,357 |
Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 156,209 |
Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 183,736 |
Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 135,167 |
A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 131,421 |
A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 10,170 |
A3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 10,120 |
Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 1,457,246 |
State and municipal |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 1,114,874 | $ 1,117,552
State and municipal | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 108,774 |
State and municipal | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 156,209 |
State and municipal | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 183,736 |
State and municipal | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 135,167 |
State and municipal | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 131,421 |
State and municipal | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 10,170 |
State and municipal | A3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 10,120 |
State and municipal | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 379,277 |
Other |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 1,148,552 |
Other | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 70,583 |
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 | $ 1,077,969 |

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