FAIR VALUE, Quantitative Information About Level 3 Fair Value Measurements (Details) - Recurring $ in Millions	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Private Equity Funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Private equity investments not measured at NAV	$ 37	$ 63
Level 3 | Private Equity Funds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Private equity investments not measured at NAV	$ 37	$ 63
Level 3 | Other Investment - Private Equity Investments | Discount Rate | Transaction price or other investment-specific events
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	25	25
Level 3 | Other Investment - Private Equity Investments | Discount Rate | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	25	25
Level 3 | Other Investment - Private Equity Investments | EBITDA Multiple | Transaction price or other investment-specific events
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	9.0	12.5
Level 3 | Other Investment - Private Equity Investments | EBITDA Multiple | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	9.0	12.5