| **Self-Insured Risks - Textual (Details) $ in Millions**     | Dec. 31, 2016 USD ($) claim | Dec. 31, 2015 USD ($) claim |
|--------------------------------------------------------------|-----------------------------|-----------------------------|
| **Insurance [Abstract]**                                     |                        |                        |
| Maximum first layer of insurance coverage funded             | $ 28.0                      |                        |
| Self-insurance reserves included in Other currentliabilities | $ 61.0                      | $ 40.5                      |
| Number of individual claims covered by reserves | claim      | 1,000                       | 1,100                       |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Maximum amount that would be funded by the Company's wholly-owned captive insurance subsidiary to insure a portion of our professional liability, general liability, and workers' compensation risks through a self-insured retention program.
+ References
No definition available.
+ Details**Name:**hls_MaximumSelfInsuredRisk**Namespace Prefix:**hls_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of individual claims covered by the Company's self-insured risk reserves.
+ References
No definition available.
+ Details**Name:**hls_NumberOfIndividualClaimsCoveredBySelfInsuredRiskReserves**Namespace Prefix:**hls_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**us-gaap_InsuranceAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount of accrued known and estimated losses incurred as of the balance sheet date for which no insurance coverage exists, and for which a claim has been made or is probable of being asserted, typically arising from workmen's compensation-type of incidents and personal injury to nonemployees from accidents on the entity's property that are expected to be paid within one year (or the normal operating cycle, if longer).
+ References
No definition available.
+ Details**Name:**us-gaap_SelfInsuranceReserveCurrent**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |