| **Long-term Debt (Tables)**                         | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
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| **Debt Disclosure [Abstract]**                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
| Schedule of Outstanding Long-term Debt              | Our long-term debt outstanding consists of the following (in millions): As of December 31, 2011 2010Credit Agreement—   Advances under $500 million revolving credit facility$110.0 $78.0Term loan facility97.5 —Bonds payable—   10.75% Senior Notes due 2016— 495.57.25% Senior Notes due 2018336.7 275.08.125% Senior Notes due 2020285.8 285.57.75% Senior Notes due 2022312.0 250.0Other bonds payable1.5 1.8Other notes payable35.3 36.4Capital lease obligations75.9 89.1 1,254.7 1,511.3Less: Current portion(18.9) (14.5)Long-term debt, net of current portion$1,235.8 $1,496.8 |
| Schedule of Debt Maturities                         | The following chart shows scheduled principal payments due on long-term debt for the next five years and thereafter (in millions):Year Ending December 31, Face Amount Net Amount2012 $18.9 $18.92013 18.1 18.12014 16.8 16.82015 16.9 16.92016 184.3 184.3Thereafter 1,000.2 999.7Total $1,255.2 $1,254.7                                                                                                                                                                                                                                                                                                                                      |
| Schedule of Redemption Prices for 2018 Senior Notes | We may redeem the notes, in whole or in part, at any time on or after October 1, 2014, at the redemption prices set forth below:Period RedemptionPrice*2014 103.625%2015 101.813%2016 and thereafter 100.000%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Schedule of Redemption Prices for 2022 Senior Notes | We may redeem the notes, in whole or in part, at any time on or after September 15, 2015, at the redemption prices set forth below:Period RedemptionPrice*2015 103.875%2016 102.583%2017 101.292%2018 and thereafter 100.000%                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| Schedule of Redemption Prices for 2020 Senior Notes | We may redeem the notes, in whole or in part, at any time on or after February 15, 2015, at the redemption prices set forth below:Period Redemption Price*2015 104.063%2016 102.708%2017 101.354%2018 and thereafter 100.000%                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |

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| - Definition
Tabular disclosure of redemption prices by year and expressed as a percentage of face value for the Company's Senior Notes due 2018.
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No definition available.
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Tabular disclosure of redemption prices by year and expressed as a percentage of face value for the Company's Senior Notes due 2020.
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| - Definition
Tabular disclosure of redemption prices by year and expressed as a percentage of face value for the Company's Senior Notes due 2022.
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| - Definition
Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.
+ References
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| - Definition
Tabular disclosure of the combined aggregate amount of maturities and sinking fund requirements for all long-term borrowings for each of the five years following the date of the latest balance sheet date presented.
+ References
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