| **Employee Retirement Benefits - Defined Contribution Plan (Detail) - USD ($) $ in Millions** | 3 Months Ended | 6 Months Ended |
|-----------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Defined Benefit Plan Disclosure [Line Items]**                                              |           |           |   |   |   |
| Matching contributions to 401(k) and Top Hat plans                                            |           | $ 4            | $ 3 | $ 8 | $ 7 |
| Qualified Pension Plans [Member]                                                              |           |           |   |   |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                              |           |           |   |   |   |
| Expected contributions by employer in the remainder of year                                   |           | $ 0            |   | 0 |   |
| Pension contributions                                                                         |           |           |   | $ 5 |   |
| Forecast [Member] | Qualified Pension Plans [Member]                                          |           |           |   |   |   |
| **Defined Benefit Plan Disclosure [Line Items]**                                              |           |           |   |   |   |
| Pension contributions                                                                         | $ 8            |           |   |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of benefits from a defined benefit plan expected to be paid in the remainder of the fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of discretionary contributions made by an employer to a defined contribution plan.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of cash or cash equivalents contributed by the entity to fund its pension plans.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3536-108585
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| X                                                                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------|
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