COMMITMENTS, CONTINGENCIES AND GUARANTEES, Summary of Off-Balance Sheet Risks (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Open-end consumer lines of credit (primarily SBL)	$ 17,515	$ 12,148
Commercial lines of credit	2,075	1,482
Unfunded lending commitments	548	532
Standby letters of credit	$ 22	$ 33