VARIABLE INTEREST ENTITIES, Primary Beneficiary - Carrying Value of Assets, Liabilities and Equity (Details) - USD ($) $ in Millions	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021
Assets:
Cash and cash equivalents and assets segregated for regulatory purposes and restricted cash	$ 12,214	$ 14,659	$ 20,209	$ 16,449
Other assets	2,769	2,452
Total assets	77,633	80,951
Liabilities:
Other payables	1,727	1,768
Total liabilities	67,711	71,519
Noncontrolling interests	(27)	(26)
Variable Interest Entity, Primary Beneficiary
Assets:
Total assets	80	76
Liabilities:
Total liabilities	33	23
Variable Interest Entity, Primary Beneficiary | Carrying amount
Assets:
Cash and cash equivalents and assets segregated for regulatory purposes and restricted cash	5	5
Other assets	48	54
Total assets	53	59
Liabilities:
Other payables	0	0
Total liabilities	0	0
Noncontrolling interests	$ (27)	$ (26)