| **Share-Based Payments - Textual (Details) (USD $)In Millions, except Share data, unless otherwise specified**                               | 12 Months Ended                                                                                                                                                                                                    |
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| **Share-based Compensation (Textual) [Abstract]**                                                                                            |                                                                                                                                                                                                               |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value                                     | $ 7.4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue                                                                                                  | $ 8.2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue |   |
| 2008 Amended and Restated Equity Incentive Plan [Member]                                                                                     |                                                                                                                                                                                                               |   |   |
| **Share-based Compensation (Textual) [Abstract]**                                                                                            |                                                                                                                                                                                                               |   |   |
| Share-based Compensation Plan, Shares Authorized                                                                                             | 9,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized/ us-gaap_PlanNameAxis= hls_EquityIncentivePlan2008AmendedAndRestatedMember                                      | 9,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized/ us-gaap_PlanNameAxis= hls_EquityIncentivePlan2008AmendedAndRestatedMember | 9,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized/ us-gaap_PlanNameAxis= hls_EquityIncentivePlan2008AmendedAndRestatedMember |
| Stock Options [Member]                                                                                                                       |                                                                                                                                                                                                               |   |   |
| **Share-based Compensation (Textual) [Abstract]**                                                                                            |                                                                                                                                                                                                               |   |   |
| Share-based Compensation, Options, Grants in Period, Weighted-Average Fair Value                                                             | $ 11.41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember                           | $ 10.96us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember | $ 9.57us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember |
| Share-based Compensation Expense                                                                                                             | 1.9us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember                                                                                                        | 2.1us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember | 2.0us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember |
| Share-based Compensation, Unrecognized Expense                                                                                               | 1.8us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember                                                     |   |   |
| Share-based Compensation, Unrecognized Expense, Time Period Expected to be Recognized                                                        | 20 months                                                                                                                                                                                                          |   |   |
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value                                     | 2.4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember                                          | 1.9us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember | 0.1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue/ us-gaap_AwardTypeAxis= us-gaap_EmployeeStockOptionMember |
| Restricted Stock [Member]                                                                                                                    |                                                                                                                                                                                                               |   |   |
| **Share-based Compensation (Textual) [Abstract]**                                                                                            |                                                                                                                                                                                                               |   |   |
| Share-based Compensation Expense                                                                                                             | 20.8us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                                           | 21.6us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 21.2us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Share-based Compensation, Unrecognized Expense                                                                                               | 16.4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                        |   |   |
| Share-based Compensation, Unrecognized Expense, Time Period Expected to be Recognized                                                        | 19 months                                                                                                                                                                                                          |   |   |
| Share-based Compensation, Restricted Stock Awards, Grants in Period, Weighted Average Fair Value                                             | $ 23.94us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember     | $ 23.55us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | $ 19.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value | 25.9us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                           | 15.7us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 34.0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Restricted Stock Units (RSUs) [Member]                                                                                                       |                                                                                                                                                                                                               |   |   |
| **Share-based Compensation (Textual) [Abstract]**                                                                                            |                                                                                                                                                                                                               |   |   |
| Share-based Compensation Expense                                                                                                             | 1.2us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember                                                                                                    | 1.2us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember | 0.9us-gaap_AllocatedShareBasedCompensationExpense/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember |
| Share-based Compensation, Unrecognized Expense                                                                                               | $ 0us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember                                                 |   |   |
| Share-based Compensation Plan, Restricted Stock Units, Issued in Period                                                                      | 36,350hls_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember                                   | 51,180hls_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember | 42,903hls_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember |
| Share-based Compensation Plan, Restricted Stock Units, Issued in Period, Weighted Average Grant Date Fair Value                              | $ 33.02hls_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember | $ 22.47hls_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember | $ 20.98hls_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember |
| Share-based Compensation Plan, Restricted Stock Units As Dividend Equivalents, Issued in Period                                              | 8,149hls_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsasDividendEquivalentsIssuedinPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember               | 1,831hls_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsasDividendEquivalentsIssuedinPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember |   |
| Share-based Compensation Plan, Number of Shares Available for Grant                                                                          | 353,466us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockUnitsRSUMember                                              |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
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| - Definition
Under a share-based compensation plan, the number of shares of equity instruments, other than options, issued during the period as dividend equivalents.
+ References
No definition available.
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| - Definition
Under a share-based compensation plan, the number of shares of equity instruments, other than options, issued during the period that are fully vested when awarded (i.e. no vesting period).
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                               |
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| - Definition
The weighted average fair value at the issue date for fully-vested equity-based instruments awarded during the period.
+ References
No definition available.
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| - Definition
Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Unrecognized cost of unvested share-based compensation awards.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.
+ References
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| X                                                                                                                                           |
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| X                                                                                                                                                                |
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