| **Long-term Debt - Senior Notes Redemption Prices (Details) - Senior Notes [Member]** | 12 Months Ended |
|---------------------------------------------------------------------------------------|-----------------|
||
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 101.00%         |
| 5.125% Senior Notes Due 2023 [Member] | Redemption Period One [Member]                |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 103.844%        |
| 5.125% Senior Notes Due 2023 [Member] | Redemption Period Two [Member]                |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 102.563%        |
| 5.125% Senior Notes Due 2023 [Member] | Redemption Period Three [Member]              |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 101.281%        |
| 5.125% Senior Notes Due 2023 [Member] | Redemption Period Four [Member]               |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 100.00%         |
| 5.75% Senior Notes Due 2024 [Member] | Redemption Period One [Member]                 |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 102.875%        |
| 5.75% Senior Notes Due 2024 [Member] | Redemption Period Two [Member]                 |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 101.917%        |
| 5.75% Senior Notes Due 2024 [Member] | Redemption Period Three [Member]               |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 100.958%        |
| 5.75% Senior Notes Due 2024 [Member] | Redemption Period Four [Member]                |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 100.00%         |
| 5.75% Senior Notes Due 2025 [Member] | Redemption Period One [Member]                 |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 102.875%        |
| 5.75% Senior Notes Due 2025 [Member] | Redemption Period Two [Member]                 |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 101.917%        |
| 5.75% Senior Notes Due 2025 [Member] | Redemption Period Three [Member]               |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 100.958%        |
| 5.75% Senior Notes Due 2025 [Member] | Redemption Period Four [Member]                |            |
| **Debt Instrument, Redemption [Line Items]**                                          |            |
| Redemption price, (percent)                                                           | 100.00%         |

| X                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
+ Details**Name:**us-gaap_DebtInstrumentRedemptionLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph e -URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823
+ Details**Name:**us-gaap_DebtInstrumentRedemptionPricePercentage**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=hls_SeniorNotes05.125Due2023Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodOneMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodTwoMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodThreeMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentRedemptionPeriodAxis=us-gaap_DebtInstrumentRedemptionPeriodFourMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=hls_SeniorNotes0575Due2024Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DebtInstrumentAxis=hls_SeniorNotes05.75Due2025Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |