| **Long-term Debt - Table 1 (Details) (USD $)In Millions, unless otherwise specified** | Mar. 31, 2015                                                                                                                      | Dec. 31, 2014                                                                                                                      |
|---------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------|
| **Schedule of Outstanding Long-term Debt**                                            |                                                                                                                               |                                                                                                                               |
| Advances under revolving credit facility                                              | $ 10.0us-gaap_LineOfCredit                                                                                                         | $ 325.0us-gaap_LineOfCredit                                                                                                        |
| Term loan facilities                                                                  | 197.5us-gaap_LoansPayableToBank                                                                                                    | 450.0us-gaap_LoansPayableToBank                                                                                                    |
| Other notes payable                                                                   | 41.1us-gaap_OtherNotesPayable                                                                                                      | 41.6us-gaap_OtherNotesPayable                                                                                                      |
| Capital lease obligations                                                             | 85.2us-gaap_CapitalLeaseObligations                                                                                                | 86.7us-gaap_CapitalLeaseObligations                                                                                                |
| Total debt and capital lease obligations                                              | 2,272.3us-gaap_DebtAndCapitalLeaseObligations                                                                                      | 2,131.6us-gaap_DebtAndCapitalLeaseObligations                                                                                      |
| Less: Current portion                                                                 | (149.8)us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent                                                                       | (20.8)us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent                                                                        |
| Long-term debt, net of current portion                                                | 2,122.5us-gaap_LongTermDebtAndCapitalLeaseObligations                                                                              | 2,110.8us-gaap_LongTermDebtAndCapitalLeaseObligations                                                                              |
| 8.125% Senior Notes Due 2020 [Member]                                                 |                                                                                                                               |                                                                                                                               |
| **Schedule of Outstanding Long-term Debt**                                            |                                                                                                                               |                                                                                                                               |
| Senior Notes                                                                          | 287.2us-gaap_SeniorNotes/ us-gaap_LongtermDebtTypeAxis= hls_SeniorNotes08125Due2020Member                                          | 287.0us-gaap_SeniorNotes/ us-gaap_LongtermDebtTypeAxis= hls_SeniorNotes08125Due2020Member                                          |
| 7.75% Senior Notes Due 2022 [Member]                                                  |                                                                                                                               |                                                                                                                               |
| **Schedule of Outstanding Long-term Debt**                                            |                                                                                                                               |                                                                                                                               |
| Senior Notes                                                                          | 227.1us-gaap_SeniorNotes/ us-gaap_LongtermDebtTypeAxis= hls_SeniorNotes0775Due2022Member                                           | 227.1us-gaap_SeniorNotes/ us-gaap_LongtermDebtTypeAxis= hls_SeniorNotes0775Due2022Member                                           |
| 5.125% Senior Notes Due 2023 [Member]                                                 |                                                                                                                               |                                                                                                                               |
| **Schedule of Outstanding Long-term Debt**                                            |                                                                                                                               |                                                                                                                               |
| Senior Notes                                                                          | 300.0us-gaap_SeniorNotes/ us-gaap_LongtermDebtTypeAxis= hls_SeniorNotes05.125Due2023Member                                         | 0us-gaap_SeniorNotes/ us-gaap_LongtermDebtTypeAxis= hls_SeniorNotes05.125Due2023Member                                             |
| 5.75% Senior Notes Due 2024 [Member]                                                  |                                                                                                                               |                                                                                                                               |
| **Schedule of Outstanding Long-term Debt**                                            |                                                                                                                               |                                                                                                                               |
| Senior Notes                                                                          | 864.0us-gaap_SeniorNotes/ us-gaap_LongtermDebtTypeAxis= hls_SeniorNotes0575Due2024Member                                           | 456.2us-gaap_SeniorNotes/ us-gaap_LongtermDebtTypeAxis= hls_SeniorNotes0575Due2024Member                                           |
| 2.00% Convertible Senior Subordinated Notes due 2043 [Member]                         |                                                                                                                               |                                                                                                                               |
| **Schedule of Outstanding Long-term Debt**                                            |                                                                                                                               |                                                                                                                               |
| Convertible Subordinated Debt                                                         | $ 260.2us-gaap_ConvertibleSubordinatedDebt/ us-gaap_LongtermDebtTypeAxis= hls_A2.00ConvertibleSeniorSubordinatedNotesdue2043Member | $ 258.0us-gaap_ConvertibleSubordinatedDebt/ us-gaap_LongtermDebtTypeAxis= hls_A2.00ConvertibleSeniorSubordinatedNotesdue2043Member |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
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| - Definition
Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including the current and noncurrent portions, the carrying value of convertible subordinated debt, as of the balance sheet date, initially scheduled to be repaid after one year or beyond the normal operating cycle if longer. This form of debt can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder, and places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including the current and noncurrent portions, carrying value as of the balance sheet date of loans from a bank with maturities initially due after one year or beyond the normal operating cycle if longer.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.
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| - Definition
Amount of long-term debt and capital leases due within one year or the normal operating cycle, if longer.
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including the current and noncurrent portions, the carrying value of notes payable which were initially due after one year or beyond the normal operating cycle, if longer, and which are not otherwise defined in the taxonomy.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.
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