FAIR VALUE, Investments in Private Equity Measured at Net Asset Value Per Share (Details) - Recurring - USD ($) $ in Millions	Mar. 31, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Private equity investments measured at NAV, recorded value	$ 99	$ 101
Private equity investments not measured at NAV, recorded value	7	7
Total private equity investments	106	108
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Fair Value, Assets and Liabilities Measured on Nonrecurring Basis [Line Items]
Private equity investments measured at NAV, unfunded commitment	$ 26	$ 29