DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Income Statement Location (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ 22	$ 13	$ 7
Interest rate | Principal transactions
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, location	Principal transactions	Principal transactions	Principal transactions
Interest rate | Revenue from contract with customer | Other revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives, location	Revenue from contract with customer	Revenue from contract with customer	Revenue from contract with customer
Foreign exchange
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ 102	$ (21)	$ 0
Gain (loss) on derivatives, location	Revenue from contract with customer	Revenue from contract with customer	Revenue from contract with customer
Other
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ (1)	$ 4	$ (5)
Gain (loss) on derivatives, location	Principal transactions	Principal transactions	Principal transactions