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Employee Benefits - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2016 USD ($)
Defined Contribution Plan Disclosure [Line Items] |
Defined benefit plan contribution by employer | $ 0
Minimum [Member] |
Defined Contribution Plan Disclosure [Line Items] |
Defined contribution plan eligibility years of age for employees | 21 years

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- Definition Defined Contribution Plan Employee Eligibility Age + References No definition available. + Details
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Namespace Prefix: | hsgx_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |