VARIABLE INTEREST ENTITIES, Not the Primary Beneficiary - Aggregate Assets, Liabilities Exposure to Loss (Details) - USD ($) $ in Millions	Mar. 31, 2023	Sep. 30, 2022
Variable Interest Entity [Line Items]
Aggregate assets	$ 79,180	$ 80,951
Aggregate liabilities	69,211	71,519
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Aggregate assets	10,944	10,088
Aggregate liabilities	3,382	3,133
Our risk of loss	175	234
Variable Interest Entity, Not Primary Beneficiary | LIHTC funds
Variable Interest Entity [Line Items]
Aggregate assets	8,518	7,752
Aggregate liabilities	2,759	2,584
Our risk of loss	73	136
Variable Interest Entity, Not Primary Beneficiary | Private Equity Interests
Variable Interest Entity [Line Items]
Aggregate assets	2,317	2,177
Aggregate liabilities	553	448
Our risk of loss	99	90
Variable Interest Entity, Not Primary Beneficiary | Other
Variable Interest Entity [Line Items]
Aggregate assets	109	159
Aggregate liabilities	70	101
Our risk of loss	$ 3	$ 8