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Regulatory Capital - Additional Information (Detail) $ in Billions | Sep. 30, 2023 USD ($) | Mar. 31, 2020
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Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Tier 1 capital ratio of risk-weighted assets | 0.025 |
Maximum asset value required to be maintained leverage ratio | $ 10 |
Maximum [Member] |  |
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] |  |
Leverage ratio |  | 0.09

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