| **Goodwill and Other Intangible Assets - Table 1 (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended                                                                                                   |                                                                                                                                        |
|-------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------|
||
| **Schedule of Changes in the Carrying Amount of Goodwill**                                                  |                                                                                                              |                                                                                                                                   |   |   |
| Goodwill, Beginning Balance                                                                                 | $ 456.9us-gaap_Goodwill                                                                                           | $ 437.3us-gaap_Goodwill                                                                                                                | $ 421.7us-gaap_Goodwill | $ 34.6us-gaap_Goodwill |
| Goodwill, Acquisitions                                                                                      | 593.1us-gaap_GoodwillAcquiredDuringPeriod                                                                         | 13.7us-gaap_GoodwillAcquiredDuringPeriod                                                                                               |   |   |
| Goodwill, Period Increase                                                                                   |                                                                                                              |                                                                                                                                   | 15.6us-gaap_GoodwillPeriodIncreaseDecrease |   |
| Goodwill, Written off Related to Sale of Business Unit                                                      |                                                                                                              | (0.3)us-gaap_GoodwillWrittenOffRelatedToSaleOfBusinessUnit                                                                             |   |   |
| Goodwill, Ending Balance                                                                                    | 1,084.0us-gaap_Goodwill                                                                                           | 456.9us-gaap_Goodwill                                                                                                                  | 437.3us-gaap_Goodwill | 34.6us-gaap_Goodwill |
| Consolidation of Joint Venture [Member]                                                                     |                                                                                                              |                                                                                                                                   |   |   |
| **Schedule of Changes in the Carrying Amount of Goodwill**                                                  |                                                                                                              |                                                                                                                                   |   |   |
| Goodwill, Period Increase                                                                                   | 34.0us-gaap_GoodwillPeriodIncreaseDecrease/ us-gaap_ConsolidationItemsAxis= hls_ConsolidationofJointVentureMember |                                                                                                                                   | 15.6us-gaap_GoodwillPeriodIncreaseDecrease/ us-gaap_ConsolidationItemsAxis= hls_ConsolidationofJointVentureMember |   |
| Conversion of wholly owned subsidiary to joint venture [Member]                                             |                                                                                                              |                                                                                                                                   |   |   |
| **Schedule of Changes in the Carrying Amount of Goodwill**                                                  |                                                                                                              |                                                                                                                                   |   |   |
| Goodwill, Period Increase                                                                                   |                                                                                                              | $ 6.2us-gaap_GoodwillPeriodIncreaseDecrease/ us-gaap_ConsolidationItemsAxis= hls_ConversionofwhollyownedsubsidiarytojointventureMember |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of increase (decrease) of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267
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| X                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267
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| X                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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