DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Derivative Gain (Loss) Recognized in AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate (cash flow hedges)	$ 0	$ (37)	$ 1
Total gains/(losses) included in AOCI, net of taxes	39	(35)	(9)
Interest rate
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate (cash flow hedges)	0	(37)	1
Foreign exchange
Derivative Instruments, Gain (Loss) [Line Items]
Foreign exchange (net investment hedges)	$ 39	$ 2	$ (10)