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Regulation and Capital Adequacy - Additional Information (Detail) - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]    
Equity investment in subsidiaries $ 144,770 $ 140,790
Minimum equity capital that is required to be maintained in regulated subsidiaries $ 110,980 $ 98,480