| **Fair Value Measurements - Summary of Book Value and Principal Amounts of Long-Term Debt (Detail) - USD ($) $ in Millions** | 9 Months Ended | 12 Months Ended |
|------------------------------------------------------------------------------------------------------------------------------|----------------|-----------------|
||
| **Debt Instrument [Line Items]**                                                                                             |           |            |
| Book value                                                                                                                   | $ 791          | $ 791           |
| Principal amount of debt                                                                                                     | $ 793          | $ 793           |
| Senior Debentures 6.900% Due 2028                                                                                            |           |            |
| **Debt Instrument [Line Items]**                                                                                             |           |            |
| Interest rate                                                                                                                | 6.90%          | 6.90%           |
| Debt issuance year                                                                                                           | 1998           | 1998            |
| Book value                                                                                                                   | $ 28           | $ 28            |
| Principal amount of debt                                                                                                     | $ 28           | $ 28            |
| Senior Debentures 6.920% Due 2028                                                                                            |           |            |
| **Debt Instrument [Line Items]**                                                                                             |           |            |
| Interest rate                                                                                                                | 6.92%          | 6.92%           |
| Debt issuance year                                                                                                           | 2005           | 2005            |
| Book value                                                                                                                   | $ 391          | $ 391           |
| Principal amount of debt                                                                                                     | $ 391          | $ 391           |
| Senior Notes 6.152% Due 2034                                                                                                 |           |            |
| **Debt Instrument [Line Items]**                                                                                             |           |            |
| Interest rate                                                                                                                | 6.125%         | 6.125%          |
| Debt issuance year                                                                                                           | 2004           | 2004            |
| Book value                                                                                                                   | $ 372          | $ 372           |
| Principal amount of debt                                                                                                     | $ 374          | $ 374           |

| X                                                                                                                                                                                                                                          |
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Debt instrument issuance year.
+ References
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| - Definition
Face (par) amount of debt instrument at time of issuance.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Contractual interest rate for funds borrowed, under the debt agreement.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                               |
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| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.
+ References
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