| **Property and Equipment - Table 3 (Details) (USD $)In Millions, unless otherwise specified**                                                                               | 12 Months Ended                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------|
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| **Summary of Depreciation Expense, Amortization Expense Relating to Assets Under Capital Lease Obligations, Interest Capitalized, and Rent Expense Under Operating Leases** |                                                    |   |   |
| Depreciation expense                                                                                                                                                        | $ 79.9us-gaap_Depreciation                              | $ 67.9us-gaap_Depreciation | $ 59.0us-gaap_Depreciation |
| Amortization expense                                                                                                                                                        | 7.5us-gaap_AmortizationOfLeasedAsset                    | 9.5us-gaap_AmortizationOfLeasedAsset | 10.1us-gaap_AmortizationOfLeasedAsset |
| Interest capitalized                                                                                                                                                        | 1.5us-gaap_InterestCostsCapitalized                     | 1.9us-gaap_InterestCostsCapitalized | 1.0us-gaap_InterestCostsCapitalized |
| **Rent expense:**                                                                                                                                                           |                                                    |   |   |
| Minimum rent payments                                                                                                                                                       | 37.3us-gaap_OperatingLeasesRentExpenseMinimumRentals    | 40.3us-gaap_OperatingLeasesRentExpenseMinimumRentals | 41.2us-gaap_OperatingLeasesRentExpenseMinimumRentals |
| Contingent and other rents                                                                                                                                                  | 18.2us-gaap_OperatingLeasesRentExpenseContingentRentals | 20.3us-gaap_OperatingLeasesRentExpenseContingentRentals | 20.6us-gaap_OperatingLeasesRentExpenseContingentRentals |
| Other                                                                                                                                                                       | 3.9hls_OperatingLeasesRentExpenseOther                  | 4.2hls_OperatingLeasesRentExpenseOther | 4.5hls_OperatingLeasesRentExpenseOther |
| Total rent expense                                                                                                                                                          | $ 59.4us-gaap_OperatingLeasesRentExpenseNet             | $ 64.8us-gaap_OperatingLeasesRentExpenseNet | $ 66.3us-gaap_OperatingLeasesRentExpenseNet |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the payments for executory costs such as insurance, maintenance, and taxes that the lessee is obligated to make or can be required to make (apart from rental payments) in connection with a property under the terms of an agreement classified as an operating lease.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The expense charged against earnings for the periodic recognition of capitalized leases. This element may apply to energy companies that lease mineral producing properties and to other enterprises that capitalize property, plant, or equipment obtained through capital leases.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of interest capitalized during the period.
+ References
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| X                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_OperatingLeasesRentExpenseAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The increases or decreases in lease payments that result from changes occurring after the inception of the lease in the factors (other than the passage of time) on which lease payments are based, except that any escalation of minimum lease payments relating to increases in construction or acquisition cost of the leased property or for increases in some measure of cost or value during the construction or preconstruction period, are excluded from contingent rentals. Contingent rentals also may include amounts for which the triggering events have not yet occurred or the specified targets for which have not yet been achieved (such as sales based percentage rent), but which events are considered probable of occurring or which specified targets are considered probable of being achieved.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the payments that the lessee is obligated to make or can be required to make in connection with a property under the terms of an agreement classified as an operating lease, excluding contingent rentals and a guarantee by the lessee of the lessor's debt and the lessee's obligation to pay (apart from the rental payments) executory costs such as insurance, maintenance, and taxes.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.
+ References
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