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Investment Securities - Maturity of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022
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Investment Securities [Line Items] |  |  |
Due within 1 year, Amortized Cost |  | $ 6,255 |
Due after 1 but within 5 years, Amortized Cost |  | 9,796 |
Due after 5 but within 10 years, Amortized Cost |  | 46,061 |
Due after 10 years, Amortized Cost |  | 0 |
Debt securities gross, Amortized Cost |  | 62,112 |
Total debt securities, Amortized Cost |  | 1,138,425 | $ 898,702
Due within 1 year, Estimated Fair Value |  | 6,246 |
Due after 1 but within 5 years, Estimated Fair Value |  | 9,654 |
Due after 5 but within 10 years, Estimated Fair Value |  | 41,629 |
Due after 10 years, Estimated Fair Value |  | 0 |
Debt securities gross, Estimated Fair Value |  | 57,529 |
Debt Securities, Available-for-Sale |  | 1,020,986 | $ 762,661
Mortgage-Backed Securities [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost | [1] | 1,076,313 |
Debt Securities, Available-for-Sale | [1] | 963,457 |
US Government Agencies Debt Securities [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | 516,500 |
Debt Securities, Available-for-Sale |  | 468,900 |
Obligations of U.S. Government-Sponsored Enterprises [Member] |  |  |
Investment Securities [Line Items] |  |  |
Total debt securities, Amortized Cost |  | 559,800 |
Debt Securities, Available-for-Sale |  | $ 494,600 |
[1] | Mortgage Backed Securities include an amortized cost of $516.5 million and a fair value of $468.9 million for Obligations of U.S. Government agencies issued by Ginnie Mae and an amortized cost of $559.8 million and a fair value of $494.6 million for Obligations of U.S. Government-sponsored enterprises issued by Fannie Mae and Freddie Mac.

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