| **Investments in and Advances to Nonconsolidated Affiliates (Tables)**                                | 6 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 June 30,  Six Months Ended June 30, 2016 2015 2016 2015Net operating revenues$10.9 $8.9 $22.1 $17.1Operating expenses(5.8) (3.8) (12.1) (7.7)Income from continuing operations, net of tax5.0 4.8 10.0 8.7Net income5.0 4.8 10.0 8.7 |

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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.
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| - References
No definition available.
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