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Investment Securities - Analysis of Amortized Cost and Estimated Fair Values of Securities Available for Sale (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | $ 1,267,747 | $ 1,138,425
Gross Unrealized Gains |  | 5,438 | 8,182
Gross Unrealized Losses |  | (125,562) | (125,621)
Securities available for sale |  | 1,147,623 | 1,020,986
US States and Political Subdivisions Debt Securities [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | 8,510 | 9,226
Gross Unrealized Gains |  | 0 | 3
Gross Unrealized Losses |  | (983) | (1,027)
Securities available for sale |  | 7,527 | 8,202
Corporate Securities [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | 62,475 | 51,886
Gross Unrealized Gains |  | 1,454 | 145
Gross Unrealized Losses |  | (2,436) | (3,619)
Securities available for sale |  | 61,493 | 48,412
Obligations of U.S. Government-Sponsored Enterprises [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost | [1] | 413,400 |
Securities available for sale |  | 350,600 |
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage - Backed Securities - Residential [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | 413,434 | 559,769
Gross Unrealized Gains |  | 1,481 | 3,052
Gross Unrealized Losses |  | (64,331) | (68,222)
Securities available for sale |  | 350,584 | 494,599
Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | 1,000 | 1,000
Gross Unrealized Gains |  | 0 | 0
Gross Unrealized Losses |  | (54) | (85)
Securities available for sale |  | 946 | 915
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Commercial [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | 779,232 | 512,979
Gross Unrealized Gains |  | 2,489 | 4,935
Gross Unrealized Losses |  | (57,546) | (52,521)
Securities available for sale |  | 724,175 | 465,393
Obligations of U.S. Government [Member] | Mortgage - Backed Securities - Residential [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | 3,096 | 3,565
Gross Unrealized Gains |  | 14 | 47
Gross Unrealized Losses |  | (212) | (147)
Securities available for sale |  | $ 2,898 | $ 3,465
[1] | Mortgage Backed Securities include an amortized cost of $782.3 million and a fair value of $727.1 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $413.4 million and a fair value of $350.6 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac.

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