VARIABLE INTEREST ENTITIES, Not the Primary Beneficiary - Aggregate Assets, Liabilities Exposure to Loss (Details) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020
Variable Interest Entity [Line Items]
Total assets	$ 53,657	$ 47,482
Total liabilities	46,219	40,306
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets	14,314	14,481
Total liabilities	2,325	2,225
Our risk of loss	106	139
Private Equity Interests [Member] | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets	7,255	7,738
Total liabilities	98	96
Our risk of loss	73	67
LIHTC Funds [Member] | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets	6,754	6,516
Total liabilities	2,058	1,993
Our risk of loss	26	66
Other Entities [Member] | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Total assets	305	227
Total liabilities	169	136
Our risk of loss	$ 7	$ 6