FAIR VALUE, Financial Instruments Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring $ in Millions	12 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)
Loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	$ 2	$ 3
Loans held for sale | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	2	3
Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	0	0
Collateral or discounted cash flow | Residential mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	10	12
Collateral or discounted cash flow | Residential mortgage loans | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	2	2
Collateral or discounted cash flow | Residential mortgage loans | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	8	10
Collateral or discounted cash flow | Corporate loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	84	57
Collateral or discounted cash flow | Corporate loans | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	0	0
Collateral or discounted cash flow | Corporate loans | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net	$ 84	$ 57
Minimum | Collateral or discounted cash flow | Residential mortgage loans | Prepayment rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment term	7 years	7 years
Minimum | Collateral or discounted cash flow | Corporate loans | Recovery rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net, measurement input	0.22	0.24
Maximum | Collateral or discounted cash flow | Residential mortgage loans | Prepayment rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment term	12 years	12 years
Maximum | Collateral or discounted cash flow | Corporate loans | Recovery rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net, measurement input	0.65	0.66
Weighted Average | Collateral or discounted cash flow | Residential mortgage loans | Prepayment rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Prepayment term	10 years 3 months 18 days	10 years 4 months 24 days
Weighted Average | Collateral or discounted cash flow | Corporate loans | Recovery rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank loans, net, measurement input	0.53	0.47