| **Significant Accounting Policies and Recent Accounting Standards - Adoption of New Accounting Standards (Details) - USD ($) $ in Millions** | 3 Months Ended | 12 Months Ended |
|----------------------------------------------------------------------------------------------------------------------------------------------|----------------|-----------------|
||
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]**                                                             |           |            |   |   |
| Operating income                                                                                                                             | $ 272          | $ 246           |   |   |
| Adjustments for New Accounting Pronouncements                                                                                                |           |            |   |   |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]**                                                             |           |            |   |   |
| Reduction in prepaid income tax asset reclassified to beginning retained earnings                                                            | 27             |            |   |   |
| Increase in non-current deferred income taxes reclassified to beginning retained earnings                                                    | $ 27           |            |   |   |
| Adjustments for New Accounting Pronouncements | Pro Forma                                                                                    |           |            |   |   |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]**                                                             |           |            |   |   |
| Operating income                                                                                                                             |           |            |   | $ 164 |
| Adjustments for New Accounting Pronouncements | Scenario, Forecast                                                                           |           |            |   |   |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]**                                                             |           |            |   |   |
| Operating income                                                                                                                             |           |            | $ 183 |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319
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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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| X                                                                                                                                                                                                                                                                                                       |
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| - Definition
The net result for the period of deducting operating expenses from operating revenues.
+ References
No definition available.
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