VARIABLE INTEREST ENTITIES, Not the Primary Beneficiary - Aggregate Assets, Liabilities Exposure to Loss (Details) - USD ($) $ in Millions	Jun. 30, 2020	Sep. 30, 2019
Private Equity Interests
Variable interest entity, nonconsolidated, carrying amount of assets and liabilities [Abstract]
Aggregate assets	$ 4,404	$ 6,317
Aggregate liabilities	107	117
Our risk of loss	61	63
LIHTC funds
Variable interest entity, nonconsolidated, carrying amount of assets and liabilities [Abstract]
Aggregate assets	6,218	6,001
Aggregate liabilities	1,977	2,221
Our risk of loss	25	64
Other
Variable interest entity, nonconsolidated, carrying amount of assets and liabilities [Abstract]
Aggregate assets	216	205
Aggregate liabilities	130	115
Our risk of loss	5	4
Total VIEs - not primary beneficiary
Variable interest entity, nonconsolidated, carrying amount of assets and liabilities [Abstract]
Aggregate assets	10,838	12,523
Aggregate liabilities	2,214	2,453
Our risk of loss	$ 91	$ 131