VARIABLE INTEREST ENTITIES, Not the Primary Beneficiary - Aggregate Assets, Liabilities Exposure to Loss (Details) - USD ($) $ in Millions	Jun. 30, 2024	Sep. 30, 2023
Variable Interest Entity [Line Items]
Aggregate assets	$ 80,628	$ 78,360
Aggregate liabilities	69,438	68,173
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Aggregate assets	11,659	11,243
Aggregate liabilities	4,049	3,703
Our risk of loss	180	217
Variable Interest Entity, Not Primary Beneficiary | LIHTC
Variable Interest Entity [Line Items]
Aggregate assets	8,824	8,451
Aggregate liabilities	3,114	2,964
Our risk of loss	76	113
Variable Interest Entity, Not Primary Beneficiary | Private Equity Interests
Variable Interest Entity [Line Items]
Aggregate assets	2,720	2,591
Aggregate liabilities	852	655
Our risk of loss	101	101
Variable Interest Entity, Not Primary Beneficiary | Other
Variable Interest Entity [Line Items]
Aggregate assets	115	201
Aggregate liabilities	83	84
Our risk of loss	$ 3	$ 3