DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Derivative Gain (Loss) Recognized in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate (cash flow hedges)	$ 1	$ 70	$ 26
Total gains/(losses) included in AOCI, net of taxes	(9)	142	(8)
Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate (cash flow hedges)	1	70	26
Foreign exchange
Derivative Instruments, Gain (Loss) [Line Items]
Foreign exchange (net investment hedges)	$ (10)	$ 72	$ (34)