FAIR VALUE, Level 3 Financial Assets and Liabilities, Roll Forward (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 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
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	$ 0	$ (3)
Total gains/(losses) included in earnings		2
Purchases and contributions		0
Sales and distributions		1
Transfers:
Into Level 3		0
Out of Level 3		0
Fair value end of year		0
Unrealized gains/(losses) for the year included in earnings for instruments held at the end of the year		0
Trading assets | Trading assets
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of year	4	1
Total gains/(losses) included in earnings	0	(1)
Purchases and contributions	100	70
Sales and distributions	(101)	(66)
Transfers:
Into Level 3	0	0
Out of Level 3	0	0
Fair value end of year	3	4
Unrealized gains/(losses) for the year included in earnings for instruments held at the end of the year	(3)	0
Other investments | All other
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of year	30	29
Total gains/(losses) included in earnings	(3)	1
Purchases and contributions	0	0
Sales and distributions	(20)	0
Transfers:
Into Level 3	0	0
Out of Level 3	0	0
Fair value end of year	7	30
Unrealized gains/(losses) for the year included in earnings for instruments held at the end of the year	0	0
Derivative assets | Trading assets
Changes in Level 3 recurring fair value measurements, assets [Roll Forward]
Fair value beginning of year	0
Total gains/(losses) included in earnings	4
Purchases and contributions	0
Sales and distributions	0
Transfers:
Into Level 3	0
Out of Level 3	0
Fair value end of year	4	$ 0
Unrealized gains/(losses) for the year included in earnings for instruments held at the end of the year	$ 4