DERIVATIVE ASSETS AND DERIVATIVE LIABILITIES, Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Derivative [Line Items]
Gain (loss) excluded from assessment of hedge effectiveness		$ 0	$ 0	$ 0
Interest expense		305,000,000	150,000,000	$ 178,000,000
Derivative liabilities		530,000,000	228,000,000
Credit risk contract
Derivative [Line Items]
Derivative liabilities		$ 8,000,000	$ 0
Forecast | Reclassification out of Accumulated Other Comprehensive Income
Derivative [Line Items]
Interest expense	$ 25,000,000
Bank
Derivative [Line Items]
Maximum length of time hedged in cash flow hedge		5 years