COLLATERALIZED AGREEMENTS AND FINANCINGS, Encumbered Assets (Details) - USD ($) $ in Millions	Mar. 31, 2023	Sep. 30, 2022
Had the right to deliver or repledge
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial instruments, owned, at fair value	$ 982	$ 1,276
Did not have the right to deliver or repledge
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial instruments, owned, at fair value	4,753	63
Asset pledged as collateral
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial instruments, owned, at fair value	9,561	8,800
Asset pledged as collateral | Federal Home Loan Bank
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial instruments, owned, at fair value	8,768	8,009
Asset pledged as collateral | Federal Reserve Bank Of Atlanta
Financial Instruments Owned and Pledged as Collateral [Line Items]
Financial instruments, owned, at fair value	$ 793	$ 791