DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Income Statement Location (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Principal transactions/other revenues | Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	$ 4	$ 5
Other revenues | Foreign exchange
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	(26)	(11)
Principal transactions | Other
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of derivative asset or liability	$ 4	$ 0