COMMITMENTS, CONTINGENCIES AND GUARANTEES, Summary of Off-Balance Sheet Risks (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Open-end consumer lines of credit (primarily SBL)	$ 12,148	$ 9,328
Commercial lines of credit	1,482	1,527
Unfunded loan commitments	532	599
Standby letters of credit	$ 33	$ 40