| **Business Combinations Business Combinations - Table 2 (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 |
| Encompass [Member]                                                                                                 |                                                                                                                                            |   |   |
| **Business Acquisition [Line Items]**                                                                              |                                                                                                                                            |   |   |
| Cash Acquired from Acquisition                                                                                     | 20.9us-gaap_CashAcquiredFromAcquisition/ us-gaap_BusinessAcquisitionAxis= hls_EncompassMember                                                   |   |   |
| **Net Cash Paid For All Acquisitions During Each Period Presented**                                                |                                                                                                                                            |   |   |
| Fair value of assets acquired, net of $20.9 million of cash acquired                                               | 260.1us-gaap_FairValueOfAssetsAcquired/ us-gaap_BusinessAcquisitionAxis= hls_EncompassMember                                                    |   |   |
| Goodwill                                                                                                           | 592.5us-gaap_GoodwillAcquiredDuringPeriod/ us-gaap_BusinessAcquisitionAxis= hls_EncompassMember                                                 |   |   |
| Fair value of liabilities assumed                                                                                  | (113.5)us-gaap_NoncashOrPartNoncashAcquisitionOtherLiabilitiesAssumed1/ us-gaap_BusinessAcquisitionAxis= hls_EncompassMember                    |   |   |
| Redeemable noncontrolling interests                                                                                | (64.5)us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable/ us-gaap_BusinessAcquisitionAxis= hls_EncompassMember |   |   |
| Net cash paid for acquisitions                                                                                     | $ 674.6us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired/ us-gaap_BusinessAcquisitionAxis= hls_EncompassMember                               |   |   |

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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The fair value of assets acquired in noncash investing or financing activities.
+ References
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| - 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.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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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| - Definition
The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.
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