v3.26.1
FAIR VALUE, Financial Instruments Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring
$ in Millions
Mar. 31, 2026
USD ($)
Sep. 30, 2025
USD ($)
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Loans held for sale $ 5 $ 31
Level 2    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Loans held for sale 5 31
Level 3    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Loans held for sale 0 0
Residential mortgage loans | Collateral or discounted cash flow    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net $ 11 $ 12
Residential mortgage loans | Collateral or discounted cash flow | Prepayment rate | Minimum    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net, measurement input 7 7
Residential mortgage loans | Collateral or discounted cash flow | Prepayment rate | Maximum    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net, measurement input 12 12
Residential mortgage loans | Collateral or discounted cash flow | Prepayment rate | Weighted average    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net, measurement input 10.6 10.5
Residential mortgage loans | Level 2 | Collateral or discounted cash flow    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net $ 4 $ 5
Residential mortgage loans | Level 3 | Collateral or discounted cash flow    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net 7 7
Corporate loans | Collateral or discounted cash flow    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net $ 155 $ 179
Corporate loans | Collateral or discounted cash flow | Recovery rate | Minimum    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net, measurement input 0.55 0.24
Corporate loans | Collateral or discounted cash flow | Recovery rate | Maximum    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net, measurement input 0.87 0.96
Corporate loans | Collateral or discounted cash flow | Recovery rate | Weighted average    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net, measurement input 0.74 0.76
Corporate loans | Level 2 | Collateral or discounted cash flow    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net $ 0 $ 0
Corporate loans | Level 3 | Collateral or discounted cash flow    
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]    
Bank loans, net $ 155 $ 179