FAIR VALUE, Investments in Private Equity Measured at Net Asset Value Per Share (Details) - Other investments - private equity - Recurring - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity investments measured at NAV, recorded value	$ 94	$ 79
Private equity investments not measured at NAV, recorded value	75	37
Total private equity investments	169	116
Parent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity investments measured at NAV, unfunded commitment	8	9
Total private equity investments	120	90
Noncontrolling Interest
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total private equity investments	$ 49	$ 26