COLLATERALIZED AGREEMENTS AND FINANCINGS, Repurchase Agreements and Securities Lending Transactions Accounted for as Secured Borrowings (Details) - Maturity Overnight and Continuous - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	$ 402	$ 157
Total collateralized financings	938	337
Government and agency obligations
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	206	122
Agency MBS and agency CMOs
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	196	35
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities loaned	$ 536	$ 180