FAIR VALUE, Investments in Private Equity Measured at Net Asset Value Per Share (Details) - Other investments - private equity - Recurring - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity investments measured at NAV	$ 79	$ 83
Private equity investments not measured at NAV	37	63
Total private equity investments	116	146
Noncontrolling Interest
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total private equity investments	26	47
Parent
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Private equity investments measured at NAV	9	15
Total private equity investments	$ 90	$ 99