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INVESTMENT SECURITIES - Summary of Amortized Cost of Investment Securities Held to Maturity Aggregated by Credit Quality Indicator (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | $ 1,995,733 | $ 2,074,465
Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 999,020 | 1,107,845
Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 200,380 | 148,923
Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 177,970 | 184,341
Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 180,534 | 185,166
A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 59,635 | 65,665
A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 20,329 | 20,317
Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 357,865 | 362,208
U.S. Government-sponsored agency securities |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 330,430 | 345,531
U.S. Government-sponsored agency securities | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 330,430 | 345,531
U.S. Government-sponsored agency securities | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored agency securities | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored agency securities | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored agency securities | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored agency securities | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored agency securities | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
State and municipal |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 1,072,380 | 1,085,921
State and municipal | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 75,667 | 120,801
State and municipal | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 200,380 | 148,923
State and municipal | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 177,970 | 184,341
State and municipal | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 180,534 | 185,166
State and municipal | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 59,635 | 65,665
State and municipal | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 20,329 | 20,317
State and municipal | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 357,865 | 360,708
U.S. Government-sponsored mortgage-backed securities |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 592,923 | 641,513
U.S. Government-sponsored mortgage-backed securities | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 592,923 | 641,513
U.S. Government-sponsored mortgage-backed securities | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored mortgage-backed securities | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored mortgage-backed securities | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored mortgage-backed securities | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored mortgage-backed securities | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | 0 | 0
U.S. Government-sponsored mortgage-backed securities | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total | $ 0 | 0
Foreign investment |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total |  | 1,500
Foreign investment | Aaa |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total |  | 0
Foreign investment | Aa1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total |  | 0
Foreign investment | Aa2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total |  | 0
Foreign investment | Aa3 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total |  | 0
Foreign investment | A1 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total |  | 0
Foreign investment | A2 |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total |  | 0
Foreign investment | Non-rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Total |  | $ 1,500

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