| **Fair Value Measurements (Tables)**                                          | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
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| **Fair Value Disclosures [Abstract]**                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis    | Our financial assets and liabilities that are measured at fair value on a recurring basis are as follows (in millions):    Fair Value Measurements at Reporting Date UsingAs of December 31, 2014 Fair Value Quoted Prices in Active Markets for Identical Assets(Level 1) Significant Other Observable Inputs(Level 2) Significant Unobservable Inputs(Level 3) Valuation Technique (1)Prepaid expenses and other current assets:          Current portion of restricted marketable securities $4.6 $— $4.6 $— MOther long-term assets:          Restricted marketable securities 45.9 — 45.9 — MAs of December 31, 2013          Prepaid expenses and other current assets:          Current portion of restricted marketable securities $4.7 $— $4.7 $— MOther long-term assets:          Restricted marketable securities 42.9 — 42.9 — M(1) The three valuation techniques are: market approach (M), cost approach (C), and income approach (I). |
| Schedule of Carrying Amounts and Estimated Fair Values, Financial Instruments | The carrying amounts and estimated fair values for our other financial instruments are presented in the following table (in millions): As of December 31, 2014 As of December 31, 2013 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair ValueLong-term debt:       Advances under revolving credit facility$325.0 $325.0 $45.0 $45.0Term loan facilities450.0 450.0 — —7.25% Senior Notes due 2018— — 272.4 291.48.125% Senior Notes due 2020287.0 302.5 286.6 319.47.75% Senior Notes due 2022227.1 240.7 252.5 275.05.75% Senior Notes due 2024456.2 471.4 275.0 273.62.00% Convertible Senior Subordinated Notes due 2043258.0 358.4 249.5 339.7Other notes payable41.6 41.6 47.6 47.6Financial commitments:       Letters of credit— 31.8 — 36.5                                                                                                                                                                                                                                                                                                                                                                               |

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| - Definition
Tabular disclosure of the carrying amounts and estimated fair values for the Company's financial instruments as of the balance sheet dates presented.
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No definition available.
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| - Definition
Tabular disclosure of assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19190-110258
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