| **Investments in and Advances to Nonconsolidated Affiliates (Tables)**            | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
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| **Investments in and Advances to Affiliates, Schedule of Investments [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 September 30,  Nine Months Ended September 30, 2016 2015 2016 2015Net operating revenues$11.3 $9.2 $33.4 $26.3Operating expenses(6.0) (4.0) (18.1) (11.7)Income from continuing operations, net of tax5.2 5.1 15.2 13.8Net income5.2 5.1 15.2 13.8 |

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| - Definition
Tabular disclosure of equity method investments including, but not limited to, name of each investee or group of investments, percentage ownership, difference between recorded amount of an investment and the value of the underlying equity in the net assets, and summarized financial information.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571
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| - References
No definition available.
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