| **Long-term Debt**             | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
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| **Debt Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Long-term Debt                 | Long-term DebtOur 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 $1,239.9The 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 $1,319.9In June 2013, we amended our existing credit agreement to, among other things, permit unlimited restricted payments (as defined in the credit agreement) so long as the senior secured leverage ratio remains less than or equal to 1.5x and to extend the maturity date of the revolving credit facility from August 2017 to June 2018. All other material terms of the existing credit agreement remained the same and are described in more detail in Note 8, Long-term Debt, to the consolidated financial statements accompanying the 2012 Form 10‑K. On October 29, 2013, we gave notice of our intent to redeem $30.2 million and $27.9 million of the outstanding principal amount of our existing 7.25% Senior Notes due 2018 and our existing 7.75% Senior Notes due 2022, respectively. Pursuant to the terms of these senior notes, this optional redemption represents 10% of the outstanding principal amount of the notes at a price of 103%, which will result in a total cash outlay of approximately $60 million to retire the $58.1 million in principal. This redemption is expected to close in November 2013 and is expected to be funded using a combination of cash on hand and availability under our revolving credit facility. As a result of this redemption, we expect to record an approximate $2 millionLoss on early extinguishment of debt in the fourth quarter of 2013. Our bonds payable were issued pursuant to an indenture (the “Base Indenture”) between us and The Bank of Nova Scotia Trust Company of New York, as trustee (the “Original Trustee”), as supplemented by subsequent supplemental indentures relating to each respective series of senior notes (collectively with the Base Indenture, the “Indenture”). The Original Trustee notified us of its intention to discontinue its corporate trust operations and, accordingly, to resign upon the appointment of a successor trustee. Effective July 29, 2013, Wells Fargo Bank, National Association, was appointed as successor trustee under the Indenture.For additional information regarding our indebtedness, see Note 8, Long-term Debt, to the consolidated financial statements accompanying the 2012 Form 10-K. |

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| - Definition
The entire disclosure for long-term debt.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
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