| **Cash and Marketable Securities - Textual (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended                                                                    |
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| **Cash and Marketable Securities (Textual) [Abstract]**                                               |                                                                               |   |   |
| Restricted marketable securities included in other long-term assets                                   | $ 45.9us-gaap_MarketableSecuritiesRestrictedNoncurrent                             | $ 42.9us-gaap_MarketableSecuritiesRestrictedNoncurrent |   |
| Impairment charges related to restricted marketable securities                                        | $ 0us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities | $ 0us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities | $ 0us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities |

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| - Details**Name:**hls_CashAndMarketableSecuritiesTextualAbstract**Namespace Prefix:**hls_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
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| - Definition
Total debt and equity financial instruments including: (1) securities held-to-maturity, (2) trading securities, and (3) securities available-for-sale which are intended to be held for greater than one year or the normal operating cycle, whichever is longer and that are pledged to one or more secured parties who have the right to buy, sell, or re-pledge the collateral.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(b)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 6 -Article 9Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph b -Article 4
+ Details**Name:**us-gaap_MarketableSecuritiesRestrictedNoncurrent**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
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| - Definition
The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563
+ Details**Name:**us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |