FAIR VALUE, Level 3 Financial Assets and Liabilities, Roll Forward (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 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
Revenue From Contract With Customer | Other Revenues
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 curring fair value measurements, liabilities [Roll Forward]
Fair value beginning of year	$ (3)	$ (1)
Total gains/(losses) included in earnings	2	(2)
Purchases and contributions	0	0
Sales and distributions	1	0
Transfers:
Into Level 3	0	0
Out of Level 3	0	0
Fair value end of year	0	(3)
Unrealized gains/(losses) for the year included in earnings for instruments held at the end of the year	0	(2)
Trading assets | Trading assets
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of year	1	14
Total gains/(losses) included in earnings	(1)	1
Purchases and contributions	70	108
Sales and distributions	(66)	(122)
Transfers:
Into Level 3	0	0
Out of Level 3	0	0
Fair value end of year	4	1
Unrealized gains/(losses) for the year included in earnings for instruments held at the end of the year	0	0
Other investments | All other
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of year	29	98
Total gains/(losses) included in earnings	1	9
Purchases and contributions	0	7
Sales and distributions	0	(73)
Transfers:
Into Level 3	0	0
Out of Level 3	0	(12)
Fair value end of year	30	29
Unrealized gains/(losses) for the year included in earnings for instruments held at the end of the year	$ 0	$ 2