VARIABLE INTEREST ENTITIES, Primary Beneficiary - Aggregate Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2020	Sep. 30, 2019
Private Equity Interests
Variable interest entity, consolidated, aggregate assets and liabilities [Abstract]
Aggregate assets	$ 34	$ 65
Aggregate liabilities	4	4
LIHTC funds
Variable interest entity, consolidated, aggregate assets and liabilities [Abstract]
Aggregate assets	75	80
Aggregate liabilities	5	5
Restricted Stock Trust Fund
Variable interest entity, consolidated, aggregate assets and liabilities [Abstract]
Aggregate assets	19	14
Aggregate liabilities	19	14
Total VIEs - primary beneficiary
Variable interest entity, consolidated, aggregate assets and liabilities [Abstract]
Aggregate assets	128	159
Aggregate liabilities	$ 28	$ 23