| **Long-term Debt (Tables)**            | 3 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): March 31, 2013 December 31, 2012Credit Agreement-   Advances under revolving credit facility$122.0 $—Bonds payable-   7.25% Senior Notes due 2018302.8 302.98.125% Senior Notes due 2020286.3 286.27.75% Senior Notes due 2022280.6 280.75.75% Senior Notes due 2024275.0 275.0Other notes payable42.3 36.8Capital lease obligations68.6 71.9 1,377.6 1,253.5Less: Current portion(12.3) (13.6)Long-term debt, net of current portion$1,365.3 $1,239.9 |
| 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): Face Amount Net AmountApril 1 through December 31, 2013$10.0 $10.0201410.7 10.720159.0 9.020169.0 9.02017130.1 130.12018310.1 311.5Thereafter899.5 897.3Total$1,378.4 $1,377.6                                                                                                                                                                                                                                                                      |

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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.
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