DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Income Statement Location (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Principal transactions/other revenues | Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	$ 0	$ 2	$ 5	$ 4
Other revenues | Foreign exchange
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	(19)	(8)	13	14
Compensation, commissions and benefits expense | Other
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	$ 0	$ 0	$ (1)	$ 5