FAIR VALUE, Carrying Amounts and Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2022	Sep. 30, 2021
Carrying amount
Financial assets:
Bank loans, net	$ 41,698	$ 24,902
Financial liabilities:
Bank deposits - certificates of deposit	1,121	878
Debt		2,037
Carrying amount | Other borrowings - Subordinated notes payable
Financial liabilities:
Debt	100
Carrying amount | Senior notes payable
Financial liabilities:
Debt	2,038
Recurring | Total estimated fair value
Financial assets:
Bank loans, net	41,201	24,955
Financial liabilities:
Bank deposits - certificates of deposit	1,109	898
Debt		2,459
Recurring | Total estimated fair value | Other borrowings - Subordinated notes payable
Financial liabilities:
Debt	98
Recurring | Total estimated fair value | Senior notes payable
Financial liabilities:
Debt	1,881
Recurring | Level 2 | Total estimated fair value
Financial assets:
Bank loans, net	96	116
Financial liabilities:
Bank deposits - certificates of deposit	490	0
Debt		2,459
Recurring | Level 2 | Total estimated fair value | Other borrowings - Subordinated notes payable
Financial liabilities:
Debt	98
Recurring | Level 2 | Total estimated fair value | Senior notes payable
Financial liabilities:
Debt	1,881
Recurring | Level 3 | Total estimated fair value
Financial assets:
Bank loans, net	41,105	24,839
Financial liabilities:
Bank deposits - certificates of deposit	619	898
Debt		$ 0
Recurring | Level 3 | Total estimated fair value | Other borrowings - Subordinated notes payable
Financial liabilities:
Debt	0
Recurring | Level 3 | Total estimated fair value | Senior notes payable
Financial liabilities:
Debt	$ 0