| **Long-term Debt (Tables)**            | 9 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): September 30, 2013 December 31, 2012Credit Agreement—   Advances under revolving credit facility$35.0 $—Bonds payable—   7.25% Senior Notes due 2018302.7 302.98.125% Senior Notes due 2020286.5 286.27.75% Senior Notes due 2022280.6 280.75.75% Senior Notes due 2024275.0 275.0Other notes payable49.7 36.8Capital lease obligations90.4 71.9 1,319.9 1,253.5Less: Current portion(13.7) (13.6)Long-term debt, net of current portion$1,306.2 $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 AmountOctober 1 through December 31, 2013$1.7 $1.7201414.1 14.120159.0 9.020169.0 9.020178.1 8.12018345.1 346.4Thereafter933.6 931.6Total$1,320.6 $1,319.9                                                                                                                                                                                                                                                                                         |

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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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