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Securities - Additional Information (Detail) - USD ($) | 1 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2022 | Sep. 30, 2022 | Sep. 30, 2021 | Aug. 25, 2022 | Jan. 10, 2022
Debt Securities, Available-for-Sale [Line Items] |  |  |  |  |
Sale of low yielding securities | $ 226,000,000 |  |  |  |
Debt securities. average yield percentage | 0.16% |  |  |  |
Reinvested in debt securities | $ 220,000,000 |  |  |  |
Reinvested debt securities, average yield percentage | 1.86% |  |  |  |
Proceeds from sales of available for sale securities |  | $ 222,474,000 | $ 0 |  |
Avaliable for sale of debt securities realized gains or losses |  |  | $ 0 |  |
United States Treasury Notes [Member] |  |  |  |  |
Debt Securities, Available-for-Sale [Line Items] |  |  |  |  |
Debt securities purchased at par value |  |  |  | $ 300,000,000 | $ 600,000,000
Debt securities. average yield percentage |  |  |  | 3.27% | 1.42%
Debt securities, average maturity term |  |  |  | 58 months | 53 months

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