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Investment Securities - Securities with gross unrealized losses (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
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Securities Held to Maturity, Gross Unrealized Losses |  |
Twelve Months or More | $ 331,240 | $ 420,143
Securities Held to Maturity, Fair Value |  |
Twelve Months or More | 1,765,487 | 1,834,527
Securities Available for Sale, Gross Unrealized Losses |  |
Less Than Twelve Months | 2,765 | 2,594
Twelve Months or More | 453,391 | 806,730
Securities Available for Sale, Fair Value |  |
Less Than Twelve Months | 550,116 | 93,830
Twelve Months or More | 2,689,366 | 4,113,658
U.S. Government agencies |  |
Securities Held to Maturity, Gross Unrealized Losses |  |
Twelve Months or More | 16,729 | 23,498
Securities Held to Maturity, Fair Value |  |
Twelve Months or More | 116,182 | 123,774
Securities Available for Sale, Gross Unrealized Losses |  |
Twelve Months or More |  | 18,789
Securities Available for Sale, Fair Value |  |
Twelve Months or More |  | 150,418
Residential mortgage-backed securities issued by U.S. government agencies or sponsored enterprises |  |
Securities Held to Maturity, Gross Unrealized Losses |  |
Twelve Months or More | 186,684 | 241,204
Securities Held to Maturity, Fair Value |  |
Twelve Months or More | 1,001,134 | 1,056,339
Securities Available for Sale, Gross Unrealized Losses |  |
Less Than Twelve Months | 484 | 294
Twelve Months or More | 146,753 | 282,129
Securities Available for Sale, Fair Value |  |
Less Than Twelve Months | 64,033 | 14,341
Twelve Months or More | 839,764 | 1,350,268
Residential collateralized mortgage-obligations issued by U.S. government agencies or sponsored enterprises |  |
Securities Held to Maturity, Gross Unrealized Losses |  |
Twelve Months or More | 58,177 | 72,057
Securities Held to Maturity, Fair Value |  |
Twelve Months or More | 328,600 | 339,664
Securities Available for Sale, Gross Unrealized Losses |  |
Less Than Twelve Months | 121 |
Twelve Months or More | 49,669 | 98,212
Securities Available for Sale, Fair Value |  |
Less Than Twelve Months | 102,208 |
Twelve Months or More | 302,001 | 454,908
Commercial mortgage-backed securities issued by U.S. government agencies or sponsored enterprises |  |
Securities Held to Maturity, Gross Unrealized Losses |  |
Twelve Months or More | 60,516 | 72,391
Securities Held to Maturity, Fair Value |  |
Twelve Months or More | 281,538 | 275,947
Securities Available for Sale, Gross Unrealized Losses |  |
Less Than Twelve Months | 268 | 792
Twelve Months or More | 76,786 | 193,788
Securities Available for Sale, Fair Value |  |
Less Than Twelve Months | 56,511 | 53,342
Twelve Months or More | 415,144 | 918,338
State and municipal obligations |  |
Securities Available for Sale, Gross Unrealized Losses |  |
Less Than Twelve Months | 372 | 1,484
Twelve Months or More | 151,775 | 170,125
Securities Available for Sale, Fair Value |  |
Less Than Twelve Months | 9,326 | 19,400
Twelve Months or More | 900,630 | 923,431
Small Business Administration loan-backed securities |  |
Securities Held to Maturity, Gross Unrealized Losses |  |
Twelve Months or More | 9,134 | 10,993
Securities Held to Maturity, Fair Value |  |
Twelve Months or More | 38,033 | 38,803
Securities Available for Sale, Gross Unrealized Losses |  |
Less Than Twelve Months | 1,520 | 24
Twelve Months or More | 26,885 | 41,697
Securities Available for Sale, Fair Value |  |
Less Than Twelve Months | 318,038 | 6,747
Twelve Months or More | 205,350 | 289,786
Corporate securities |  |
Securities Available for Sale, Gross Unrealized Losses |  |
Twelve Months or More | 1,523 | 1,990
Securities Available for Sale, Fair Value |  |
Twelve Months or More | $ 26,477 | $ 26,509

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