| **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, 2012 2011Credit Agreement—   Advances under revolving credit facility$— $110.0Term loan facility— 97.5Bonds payable—   7.25% Senior Notes due 2018302.9 336.78.125% Senior Notes due 2020286.2 285.87.75% Senior Notes due 2022280.7 312.05.75% Senior Notes due 2024275.0 —Other bonds payable— 1.5Other notes payable36.8 35.3Capital lease obligations71.9 75.9 1,253.5 1,254.7Less: Current portion(13.6) (18.9)Long-term debt, net of current portion$1,239.9 $1,235.8 |
| 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 Amount2013 $13.6 $13.62014 10.5 10.52015 8.0 8.02016 8.0 8.02017 7.1 7.1Thereafter 1,207.1 1,206.3Total $1,254.3 $1,253.5                                                                                                                                                                                                                                                                                                                                     |
| Schedule of Redemption Prices for 2024 Senior Notes | We may redeem the notes, in whole or in part, at any time on or after November 1, 2017, at the redemption prices set forth below:Period RedemptionPrice*2017 102.875%2018 101.917%2019 100.958%2020 and thereafter 100.000%* Expressed in percentage of principal amount                                                                                                                                                                                                                                                                                                                                                                                                                        |
| 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%* Expressed in percentage of principal amount                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| 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%* Expressed in percentage of principal amount                                                                                                                                                                                                                                                                                                                                                                                                                      |
| 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%* Expressed in percentage of principal amount                                                                                                                                                                                                                                                                                                                                                                                                                      |

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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 2024.
+ References
No definition available.
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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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No definition available.
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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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No definition available.
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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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