| **Business Combinations - Table 5 (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| **Net Cash Paid For All Acquisitions During Each Period Presented**                          |                                                                                                                                                                                                           |   |   |
| Goodwill                                                                                     | $ 593.1us-gaap_GoodwillAcquiredDuringPeriod                                                                                                                                                                    | $ 13.7us-gaap_GoodwillAcquiredDuringPeriod |   |
| Net cash paid for acquisitions                                                               | 694.8us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired                                                                                                                                                      | 28.9us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired | 3.1us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired |
| Series of Individually Immaterial Business Acquisitions [Member]                             |                                                                                                                                                                                                           |   |   |
| **Business Acquisition [Line Items]**                                                        |                                                                                                                                                                                                           |   |   |
| Cash Acquired from Acquisition                                                               | 5.1us-gaap_CashAcquiredFromAcquisition/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember                                                                      |   |   |
| **Net Cash Paid For All Acquisitions During Each Period Presented**                          |                                                                                                                                                                                                           |   |   |
| Fair value of assets acquired, net of $5.1 million of cash acquired                          | 60.1us-gaap_FairValueOfAssetsAcquired/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember                                                                       | 15.6us-gaap_FairValueOfAssetsAcquired/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember | 3.1us-gaap_FairValueOfAssetsAcquired/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember |
| Goodwill                                                                                     | 34.6us-gaap_GoodwillAcquiredDuringPeriod/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember                                                                    | 13.7us-gaap_GoodwillAcquiredDuringPeriod/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember | 0us-gaap_GoodwillAcquiredDuringPeriod/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember |
| Fair value of liabilities assumed                                                            | (21.2)us-gaap_NoncashOrPartNoncashAcquisitionOtherLiabilitiesAssumed1/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember                                       | (0.4)us-gaap_NoncashOrPartNoncashAcquisitionOtherLiabilitiesAssumed1/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember | 0us-gaap_NoncashOrPartNoncashAcquisitionOtherLiabilitiesAssumed1/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember |
| Fair value of noncontrolling interest owned by joint venture partner                         | (18.3)hls_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValueOfEquityInterest/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember | 0hls_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValueOfEquityInterest/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember | 0hls_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValueOfEquityInterest/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember |
| Fair value of equity interest prior to acquisition                                           | (35.0)us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember                          | 0us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember | 0us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember |
| Net cash paid for acquisitions                                                               | $ 20.2us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember                                                  | $ 28.9us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember | $ 3.1us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired/ us-gaap_BusinessAcquisitionAxis= us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember |

| X                                                                                                                                                                                                                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date.
+ References
No definition available.
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| X                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value at acquisition-date of the equity interest in the acquiree held by the acquirer, immediately before the acquisition date for businesses combined in stages.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (g)(1) -URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The fair value of assets acquired in noncash investing or financing activities.
+ References
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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
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| X                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_NoncashOrPartNoncashAcquisitionNetNonmonetaryAssetsAcquiredLiabilitiesAssumedAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of liabilities that an entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition that are not presented as a separate disclosure or otherwise listed in the existing taxonomy. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.
+ References
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| X                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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