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v3.25.1

INVESTMENT SECURITIES - Amortized cost and estimated fair value of investment securities (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2025 | Dec. 31, 2024
Available-for-Sale Portfolio: |  |
Amortized Cost | $ 3,182,289 | $ 3,192,392
Gross Unrealized Gains | 320 | 325
Gross Unrealized Losses | 355,694 | 407,003
Fair Value | 2,826,915 | 2,785,714
Held-to-Maturity Portfolio: |  |
Amortized Cost | 1,393,837 | 1,345,155
Gross Unrealized Gains | 1,051 | 448
Gross Unrealized Losses | 88,500 | 125,435
Fair Value | 1,306,388 | 1,220,168
Other equity securities, at adjusted cost |  |
Equity securities, Fair values |  | 2,400
Equity securities without readily determinable fair value amount | 78,000 | 85,100
U.S. Treasury and agency securities |  |
Available-for-Sale Portfolio: |  |
Amortized Cost | 2,391,650 | 2,389,208
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 256,733 | 305,422
Fair Value | 2,134,917 | 2,083,786
Held-to-Maturity Portfolio: |  |
Amortized Cost | 1,146,066 | 1,138,743
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 87,496 | 123,194
Fair Value | 1,058,570 | 1,015,549
Obligations of state and political subdivisions |  |
Available-for-Sale Portfolio: |  |
Amortized Cost | 424,482 | 428,204
Gross Unrealized Gains | 264 | 288
Gross Unrealized Losses | 46,260 | 41,997
Fair Value | 378,486 | 386,495
Government agency mortgage-backed securities |  |
Available-for-Sale Portfolio: |  |
Amortized Cost | 351,913 | 360,102
Gross Unrealized Gains | 56 | 37
Gross Unrealized Losses | 52,178 | 58,915
Fair Value | 299,791 | 301,224
Held-to-Maturity Portfolio: |  |
Amortized Cost | 247,771 | 206,412
Gross Unrealized Gains | 1,051 | 448
Gross Unrealized Losses | 1,004 | 2,241
Fair Value | 247,818 | 204,619
Corporate debt securities |  |
Available-for-Sale Portfolio: |  |
Amortized Cost | 8,000 | 8,000
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 229 | 303
Fair Value | 7,771 | 7,697
Government agency collateralized mortgage obligations |  |
Available-for-Sale Portfolio: |  |
Amortized Cost | 6,244 | 6,878
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 294 | 366
Fair Value | 5,950 | 6,512
Held-to-Maturity Portfolio: |  |
Amortized Cost | 0 |
Fair Value | 0 |
Federal Home Loan Bank Common Stock |  |
Other equity securities, at adjusted cost |  |
Equity securities without readily determinable fair value amount | 38,900 | 45,400
Federal Reserve Bank Common Stock |  |
Other equity securities, at adjusted cost |  |
Equity securities, Fair values | 2,600 |
Equity securities without readily determinable fair value amount | 33,300 | 33,400
Other Equity Securities |  |
Other equity securities, at adjusted cost |  |
Equity securities without readily determinable fair value amount | $ 5,800 | $ 6,300

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