FAIR VALUE, Level 3 Financial Assets and Liabilities, Roll Forward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
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		$ (4)		$ (3)
Total gains/(losses) included in earnings		0		(1)
Purchases and contributions		0		0
Sales, distributions, and deconsolidations		0		0
Transfers:
Into Level 3		0		0
Out of Level 3		0		0
Fair value end of period		(4)		(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	3	$ 4	1
Total gains/(losses) included in earnings	0	(1)	0	(1)
Purchases and contributions	31	19	60	55
Sales and distributions	(22)	(12)	(51)	(46)
Transfers:
Into Level 3	0	0	0	0
Out of Level 3	0	0	0	0
Fair value end of period	13	9	13	9
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	(1)	1	(1)	1
Other investments | Other investments
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of period	29	28	30	29
Total gains/(losses) included in earnings	0	1	(1)	0
Purchases and contributions	0	0	0	0
Sales and distributions	0	0	0	0
Transfers:
Into Level 3	0	0	0	0
Out of Level 3	0	0	0	0
Fair value end of period	29	29	29	29
Unrealized gains/(losses) for the period included in earnings for instruments held at the end of the reporting period	$ 0	$ 1	$ 0	$ 0