COLLATERALIZED AGREEMENTS AND FINANCINGS, Repurchase Agreements (Details) - Maturity overnight and continuous - USD ($) $ in Millions	Jun. 30, 2024	Sep. 30, 2023
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	$ 374	$ 157
Total	1,154	337
Government and agency obligations
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	203	122
Agency MBS and agency CMOs
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	171	35
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities loaned	$ 780	$ 180