COMMITMENTS, CONTINGENCIES AND GUARANTEES, Summary of Commitments to Extend Credit and Other Credit-Related Off-Balance Sheet Financial Instruments Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Open-end consumer lines of credit (primarily SBL)	$ 18,980	$ 17,515
Commercial lines of credit	1,919	2,075
Unfunded loan commitments	513	548
Standby letters of credit	$ 23	$ 22