DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Income Statement Location (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	$ 5	$ 7	$ 11	$ 10
Foreign exchange
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	(6)	(2)	$ (36)	$ (3)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Revenue from Contract with Customer, Including Assessed Tax	Revenue from Contract with Customer, Including Assessed Tax
Other
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	$ 0	$ (2)	$ (1)	$ 1
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Principal transactions	Principal transactions
Principal transactions | Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Principal transactions	Principal transactions
Other revenues | Interest rate | Other
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Revenue from Contract with Customer, Including Assessed Tax	Revenue from Contract with Customer, Including Assessed Tax