FAIR VALUE, Financial Instruments Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring $ in Millions	6 Months Ended	12 Months Ended
	Mar. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)
Loans held for sale
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	$ 93	$ 3
Loans held for sale | Level 2
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	93	3
Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	0	0
Collateral or discounted cash flow | Bank loans - residential
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	11	12
Collateral or discounted cash flow | Bank loans - residential | Level 2
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	2	2
Collateral or discounted cash flow | Bank loans - residential | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	9	10
Collateral or discounted cash flow | Bank loans - corporate
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	76	57
Collateral or discounted cash flow | Bank loans - corporate | Level 2
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	0	0
Collateral or discounted cash flow | Bank loans - corporate | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	$ 76	$ 57
Minimum | Collateral or discounted cash flow | Bank loans - residential | Prepayment rate
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Prepayment term	7 years	7 years
Minimum | Collateral or discounted cash flow | Bank loans - corporate | Recovery rate
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net, measurement input	0.44	0.24
Maximum | Collateral or discounted cash flow | Bank loans - residential | Prepayment rate
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Prepayment term	12 years	12 years
Maximum | Collateral or discounted cash flow | Bank loans - corporate | Recovery rate
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net, measurement input	0.80	0.66
Weighted average | Collateral or discounted cash flow | Bank loans - residential | Prepayment rate
Fair Value, Assets and Liabilities Measured on 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 | Bank loans - corporate | Recovery rate
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net, measurement input	0.63	0.47