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Employee Benefit Plans - Fair Value of Pension Plan Assets by Asset Category (Detail) - USD ($) $ in Millions | Sep. 30, 2023 | Sep. 30, 2022
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | $ 144 | $ 135
Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 13 | 9
Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 78 | 120
Other Investment Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  |  | 1
Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 53 | 5
Fair Value, Inputs, Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 16 | 10
Fair Value, Inputs, Level 1 | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 12 | 8
Fair Value, Inputs, Level 1 | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 4 | 1
Significant Observable Inputs (Level 2) [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 128 | 125
Significant Observable Inputs (Level 2) [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 1 | 1
Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 74 | 119
Significant Observable Inputs (Level 2) [Member] | Other Investment Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  |  | 1
Significant Observable Inputs (Level 2) [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 53 | 5
Cash and Cash Equivalent Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  |  | 1
Cash and Cash Equivalent Funds [Member] | Fair Value, Inputs, Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  |  | 1
Non-U.S. Equities [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 6 | 4
Non-U.S. Equities [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 6 | 4
Equity Funds [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [1] | 21 | 23
Equity Funds [Member] | Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [1] | 21 | 23
Non-U.S. Government Bonds [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 2 | 1
Non-U.S. Government Bonds [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 2 | 1
Fixed Income Funds [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [2] | 38 | 86
Fixed Income Funds [Member] | Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [2] | 38 | 86
Non-U.S. Corporate Bonds [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 3 | 2
Non-U.S. Corporate Bonds [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 3 | 2
Real Estate [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [3] | 15 | 9
Real Estate [Member] | Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [3] | 15 | 9
Mortgage Backed Securities [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 1 | 1
Mortgage Backed Securities [Member] | Significant Observable Inputs (Level 2) [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 1 | 1
Other Fixed Income [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 1 | 1
Other Fixed Income [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 1 | 1
Cash Equivalent Funds [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 4 | 1
Cash Equivalent Funds [Member] | Fair Value, Inputs, Level 1 | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 4 | 1
Insurance Contracts [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [4] | 52 | 5
Insurance Contracts [Member] | Significant Observable Inputs (Level 2) [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [4] | 52 | $ 5
Other Alternative Investments [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 1 |
Other Alternative Investments [Member] | Significant Observable Inputs (Level 2) [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | $ 1 |
[1] | The equity funds asset class includes funds that invest in U.S. equities as well as equity securities issued by companies incorporated, listed or domiciled in countries in developed and/or emerging markets. These companies may be in the small-, mid- or large-cap categories.
[2] | The fixed income funds asset class includes investments in high quality funds. High quality fixed income funds primarily invest in low-risk U.S. and non-U.S. government securities, investment-grade corporate bonds, mortgages and asset-backed securities. A significant portion of the fixed income funds include investment in long-term bond funds.
[3] | The real estate funds asset class includes funds that primarily invest in entities which are principally engaged in the ownership, acquisition, development, financing, sale and/or management of income-producing real estate properties, both commercial and residential. These funds typically seek long-term growth of capital and current income that is above average relative to public equity funds.
[4] | Insurance contracts held by the Company’s non-U.S. plans are issued by well-known, highly rated insurance companies.

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