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Employee Benefit Plans - Fair Value of Pension Plan Assets by Asset Category (Detail) - USD ($) $ in Millions | Sep. 30, 2024 | Sep. 30, 2023
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | $ 156 | $ 144
Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 14 | 13
Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 86 | 78
Other Investment Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 6 |
Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 55 | 53
Fair Value, Inputs, Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 14 | 16
Fair Value, Inputs, Level 1 | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 13 | 12
Fair Value, Inputs, Level 1 | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  |  | 4
Significant Observable Inputs (Level 2) [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 142 | 128
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 |  | 86 | 74
Significant Observable Inputs (Level 2) [Member] | Other Investment Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 6 |
Significant Observable Inputs (Level 2) [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 55 | 53
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 |  | 7 | 6
Non-U.S. Equities [Member] | Fair Value, Inputs, Level 1 | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 7 | 6
Equity Funds [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [1] | 16 | 21
Equity Funds [Member] | Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [1] | 16 | 21
Non-U.S. Government Bonds [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 2 | 2
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 | 2
Fixed Income Funds [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [2] | 46 | 38
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] | 46 | 38
Non-U.S. Corporate Bonds [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 4 | 3
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 | 3
Non-U.S. Corporate Bonds [Member] | Significant Observable Inputs (Level 2) [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 1 |
Real Estate [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [3] | 18 | 15
Real Estate [Member] | Significant Observable Inputs (Level 2) [Member] | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [3] | 18 | 15
Mortgage Backed Securities [Member] | Total Direct Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  |  | 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
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
Cash Equivalent Funds [Member] | Fair Value, Inputs, Level 1 | Total Investment Funds [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  |  | 4
Insurance Contracts [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [4] | 54 | 52
Insurance Contracts [Member] | Significant Observable Inputs (Level 2) [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets | [4] | 54 | 52
Other Alternative Investments [Member] | Alternative Investments [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Total pension plan assets |  | 1 | 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
[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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