FAIR VALUE, Carrying Amounts and Estimated Fair Value of Financial Instruments not Recorded on Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
5.75% fixed-to-floating subordinated notes, due 2030 (including premium of $2 and $0, respectively)
Financial liabilities:
Interest rate	5.75%
Carrying amount
Financial assets:
Bank loans, net	$ 43,167	$ 24,902
Financial liabilities:
Bank deposits - certificates of deposit	999	878
Carrying amount | Other Borrowings
Financial liabilities:
Debt	100
Carrying amount | Senior Notes
Financial liabilities:
Debt	2,038	2,037
Recurring | Total estimated fair value
Financial assets:
Bank loans, net	42,470	24,955
Financial liabilities:
Bank deposits - certificates of deposit	979	898
Recurring | Total estimated fair value | Other Borrowings
Financial liabilities:
Debt	95
Recurring | Total estimated fair value | Senior Notes
Financial liabilities:
Debt	1,706	2,459
Recurring | Level 2 | Total estimated fair value
Financial assets:
Bank loans, net	134	116
Financial liabilities:
Bank deposits - certificates of deposit	400	0
Recurring | Level 2 | Total estimated fair value | Other Borrowings
Financial liabilities:
Debt	95
Recurring | Level 2 | Total estimated fair value | Senior Notes
Financial liabilities:
Debt	1,706	2,459
Recurring | Level 3 | Total estimated fair value
Financial assets:
Bank loans, net	42,336	24,839
Financial liabilities:
Bank deposits - certificates of deposit	579	898
Recurring | Level 3 | Total estimated fair value | Other Borrowings
Financial liabilities:
Debt	0
Recurring | Level 3 | Total estimated fair value | Senior Notes
Financial liabilities:
Debt	$ 0	$ 0