FAIR VALUE, Level 3 Financial Assets and Liabilities, Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Principal transactions
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Location of gains (losses) included in earnings	Principal transactions	Principal transactions
Other revenues | Other
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Location of gains (losses) included in earnings	Revenue from contract with customer	Revenue from contract with customer
Derivative liabilities | Other
Changes in Level 3 recurring fair value measurements, liabilities [Roll Forward]
Fair value beginning of period	$ 0	$ (3)
Total gains/(losses) included in earnings	0	(1)
Purchases and contributions	0	0
Sales and distributions	0	0
Transfers:
Into Level 3	0	0
Out of Level 3	0	0
Fair value end of period	0	(4)
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	0	(1)
Trading assets | Trading assets
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	4	1
Total gains/(losses) included in earnings	0	0
Purchases and contributions	12	25
Sales and distributions	(15)	(20)
Transfers:
Into Level 3	0	0
Out of Level 3	0	0
Fair value end of period	1	6
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	0	(1)
Other investments | Other investments
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	30	29
Total gains/(losses) included in earnings	(1)	1
Purchases and contributions	0	0
Sales and distributions	0	0
Transfers:
Into Level 3	0	0
Out of Level 3	0	0
Fair value end of period	29	30
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	$ (1)	$ 1