| **Fair Value Measurements - Table 1 (Details) (USD $)**                                                            | 3 Months Ended                                                                                                                                                                                                                                                                                     | 12 Months Ended                                                                                                                                                                                                                                                                                    |
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| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Fair Value Measurements, Valuation Techniques                                                                      | I                                                                                                                                                                                                                                                                                                  | I                                                                                                                                                                                                                                                                                                  |
| Redeemable Noncontrolling Interest, Fair Value                                                                     | $ 84,700,000us-gaap_RedeemableNoncontrollingInterestEquityFairValue                                                                                                                                                                                                                                | $ 84,700,000us-gaap_RedeemableNoncontrollingInterestEquityFairValue                                                                                                                                                                                                                                |
| Fair Value, Inputs, Level 1 [Member]                                                                               |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Redeemable Noncontrolling Interest, Fair Value                                                                     | 0us-gaap_RedeemableNoncontrollingInterestEquityFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member                                                                                                                                                      | 0us-gaap_RedeemableNoncontrollingInterestEquityFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member                                                                                                                                                      |
| Fair Value, Inputs, Level 2 [Member]                                                                               |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Redeemable Noncontrolling Interest, Fair Value                                                                     | 0us-gaap_RedeemableNoncontrollingInterestEquityFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member                                                                                                                                                      | 0us-gaap_RedeemableNoncontrollingInterestEquityFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member                                                                                                                                                      |
| Fair Value, Inputs, Level 3 [Member]                                                                               |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Redeemable Noncontrolling Interest, Fair Value                                                                     | 84,700,000us-gaap_RedeemableNoncontrollingInterestEquityFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member                                                                                                                                             | 84,700,000us-gaap_RedeemableNoncontrollingInterestEquityFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member                                                                                                                                             |
| Other Current Assets [Member] | Restricted Marketable Securities [Member]                                          |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Restricted Marketable Securities, Fair Value                                                                       | 900,000us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherCurrentAssetsMember/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember                                                                                            | 4,600,000us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherCurrentAssetsMember/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember                                                                                          |
| Fair Value Measurements, Valuation Techniques                                                                      | M                                                                                                                                                                                                                                                                                                  | M                                                                                                                                                                                                                                                                                                  |
| Other Current Assets [Member] | Restricted Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member]   |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Restricted Marketable Securities, Fair Value                                                                       | 0us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherCurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember             | 0us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherCurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember             |
| Other Current Assets [Member] | Restricted Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member]   |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Restricted Marketable Securities, Fair Value                                                                       | 900,000us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherCurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember       | 4,600,000us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherCurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember     |
| Other Current Assets [Member] | Restricted Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member]   |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Restricted Marketable Securities, Fair Value                                                                       | 0us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherCurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember             | 0us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherCurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember             |
| Other Long-term Assets [Member] | Restricted Marketable Securities [Member]                                        |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Restricted Marketable Securities, Fair Value                                                                       | 50,200,000us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherNoncurrentAssetsMember/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember                                                                                      | 45,900,000us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherNoncurrentAssetsMember/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember                                                                                      |
| Fair Value Measurements, Valuation Techniques                                                                      | M                                                                                                                                                                                                                                                                                                  | M                                                                                                                                                                                                                                                                                                  |
| Other Long-term Assets [Member] | Restricted Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Restricted Marketable Securities, Fair Value                                                                       | 0us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherNoncurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember          | 0us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherNoncurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember          |
| Other Long-term Assets [Member] | Restricted Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Restricted Marketable Securities, Fair Value                                                                       | 50,200,000us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherNoncurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember | 45,900,000us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherNoncurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember |
| Other Long-term Assets [Member] | Restricted Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| **Fair Value, Assets and Liabilities Measured on Recurring Basis [Abstract]**                                      |                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                               |
| Restricted Marketable Securities, Fair Value                                                                       | $ 0us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherNoncurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember        | $ 0us-gaap_AvailableForSaleSecurities/ hls_FairValueByBalanceSheetLineItemsAxis= us-gaap_OtherNoncurrentAssetsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ hls_FairValueByFinancialInstrumentAxis= hls_RestrictedMarketableSecuritiesMember        |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Description of the inputs and valuation technique(s) used to measure fair value.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The aggregate fair value as of the reporting date of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.
+ References
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