v3.25.2
COLLATERALIZED AGREEMENTS AND FINANCINGS, Encumbered Assets (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Sep. 30, 2024
Asset pledged as collateral | Assets pledged with the FHLB or FRB:    
Financial Instruments Owned and Pledged as Collateral [Line Items]    
Financial instruments, owned, at fair value $ 23,741 $ 15,773
Asset pledged as collateral | Assets pledged with the FHLB or FRB: | Available-for-sale securities    
Financial Instruments Owned and Pledged as Collateral [Line Items]    
Financial instruments, owned, at fair value 2,602 3,979
Asset pledged as collateral | Assets pledged with the FHLB or FRB: | Bank loans    
Financial Instruments Owned and Pledged as Collateral [Line Items]    
Financial instruments, owned, at fair value 21,139 11,794
Had the right to deliver or repledge    
Financial Instruments Owned and Pledged as Collateral [Line Items]    
Financial instruments, owned, at fair value 1,143 1,281
Did not have the right to deliver or repledge    
Financial Instruments Owned and Pledged as Collateral [Line Items]    
Financial instruments, owned, at fair value $ 64 $ 66