| **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, 2014 2013Credit Agreement—   Advances under revolving credit facility$325.0 $45.0Term loan facilities450.0 —Bonds payable—   7.25% Senior Notes due 2018— 272.48.125% Senior Notes due 2020287.0 286.67.75% Senior Notes due 2022227.1 252.55.75% Senior Notes due 2024456.2 275.02.00% Convertible Senior Subordinated Notes due 2043258.0 249.5Other notes payable41.6 47.6Capital lease obligations86.7 88.9 2,131.6 1,517.5Less: Current portion(20.8) (12.3)Long-term debt, net of current portion$2,110.8 $1,505.2 |
| 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 Amount2015 $20.8 $20.82016 20.4 20.42017 18.6 18.62018 18.6 18.62019 496.7 496.7Thereafter 1,614.1 1,556.5Total $2,189.2 $2,131.6                                                                                                                                                                                                                                                                                                                                                              |
| Schedule of Redemption Prices for 2022 Senior Notes | We may redeem the 2022 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 2020 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                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Schedule of Redemption Prices for 2024 Senior Notes | We may redeem the 2024 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 Other Notes Payable                     | Our notes payable consist of the following (in millions): As of December 31,   2014 2013 Interest RatesSale/leaseback transactions involving real estate accounted for as financings$28.0 $28.0 8.1% to 11.2%Acquisition of an inpatient rehabilitation unit2.9 4.3 7.8%Construction of a new hospital10.4 13.5 LIBOR + 2.5%; 2.7% as of December 31, 2014Other0.3 1.8 5.7% to 6.8%Other notes payable$41.6 $47.6                                                                                                                                                                                                                                                    |

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Tabular disclosure of other notes payable.
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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 2024.
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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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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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