COMMITMENTS, CONTINGENCIES AND GUARANTEES, Summary of Commitments to Extend Credit and Other Credit-Related Off-Balance Sheet Financial Instruments Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2022	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Open-end consumer lines of credit (primarily SBL)	$ 20,686	$ 17,515
Commercial lines of credit	2,259	2,075
Unfunded loan commitments	605	548
Standby letters of credit	$ 38	$ 22