FAIR VALUE, Financial Instruments Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Dec. 31, 2021	Mar. 31, 2021	Sep. 30, 2021
Loans held for sale
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	$ 161		$ 29
Loans held for sale | Level 2
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	161		29
Loans held for sale | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	0		0
Discounted cash flow | Bank loans: impaired loans - residential
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	13		14
Discounted cash flow | Bank loans: impaired loans - residential | Level 2
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	3		3
Discounted cash flow | Bank loans: impaired loans - residential | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	10		11
Collateral or discounted cash flow | Bank loans: impaired loans - corporate
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	41		49
Collateral or discounted cash flow | Bank loans: impaired 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: impaired loans - corporate | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Bank loans, net	$ 41		$ 49
Minimum | Discounted cash flow | Bank loans: impaired loans - residential | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Prepayment term	7 years	7 years
Maximum | Discounted cash flow | Bank loans: impaired loans - residential | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Prepayment term	12 years	12 years
Weighted average | Discounted cash flow | Bank loans: impaired loans - residential | Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Prepayment term	10 years 6 months	10 years 6 months