| **Investments in and Advances to Nonconsolidated Affiliates (Tables)**                                | 3 Months Ended                                                                                                                                                                                                                                                                                                                             |
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| **Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]** |                                                                                                                                                                                                                                                                                                                                       |
| Schedule of Combined Results of Operations of Equity Method Affiliates                                | The following summarizes the combined results of operations of our equity method affiliates (on a 100% basis, in millions): Three Months Ended March 31, 2015 2014Net operating revenues$8.2 $21.3Operating expenses(3.9) (11.2)Income from continuing operations, net of tax3.9 18.5Net income3.9 18.5 |

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| - Definition
Tabular disclosure of the combined results of operations of our equity method affiliates (on a 100% basis) for the periods presented.
+ References
No definition available.
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| - Details**Name:**us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |