Employee Benefit Plans (Details 2) - Pension Plan	12 Months Ended
Dec. 31, 2019
Employee benefits plans
Period of operating history and sufficient trading volume of invested entity (minimum)	5 years
Minimum
Employee benefits plans
Period to meet policy goals	3 years
Maximum
Employee benefits plans
Period to meet policy goals	5 years
Equities
Employee benefits plans
Target (as a percent)	65.00%
Equities \| Minimum
Employee benefits plans
Target (as a percent)	50.00%
Equities \| Maximum
Employee benefits plans
Target (as a percent)	70.00%
U.S. Large Cap
Employee benefits plans
Target (as a percent)	30.00%
U.S. Large Cap \| Minimum
Employee benefits plans
Target (as a percent)	20.00%
U.S. Large Cap \| Maximum
Employee benefits plans
Target (as a percent)	40.00%
U.S. Mid Cap
Employee benefits plans
Target (as a percent)	10.00%
U.S. Mid Cap \| Minimum
Employee benefits plans
Target (as a percent)	0.00%
U.S. Mid Cap \| Maximum
Employee benefits plans
Target (as a percent)	15.00%
U.S. Small Cap
Employee benefits plans
Target (as a percent)	5.00%
U.S. Small Cap \| Minimum
Employee benefits plans
Target (as a percent)	0.00%
U.S. Small Cap \| Maximum
Employee benefits plans
Target (as a percent)	10.00%
International - Developed
Employee benefits plans
Target (as a percent)	15.00%
International - Developed \| Minimum
Employee benefits plans
Target (as a percent)	0.00%
International - Developed \| Maximum
Employee benefits plans
Target (as a percent)	25.00%
Emerging Markets
Employee benefits plans
Target (as a percent)	5.00%
Emerging Markets \| Minimum
Employee benefits plans
Target (as a percent)	0.00%
Emerging Markets \| Maximum
Employee benefits plans
Target (as a percent)	8.00%
Fixed Income
Employee benefits plans
Target (as a percent)	35.00%
Fixed Income \| Minimum
Employee benefits plans
Target (as a percent)	1.00%
Fixed Income \| Maximum
Employee benefits plans
Target (as a percent)	40.00%
Investment Grade
Employee benefits plans
Target (as a percent)	35.00%
Investment Grade \| Minimum
Employee benefits plans
Target (as a percent)	1.00%
Investment Grade \| Maximum
Employee benefits plans
Target (as a percent)	40.00%
International Developed Bonds
Employee benefits plans
Target (as a percent)	0.00%
International Developed Bonds \| Minimum
Employee benefits plans
Target (as a percent)	0.00%
International Developed Bonds \| Maximum
Employee benefits plans
Target (as a percent)	5.00%
High Yield
Employee benefits plans
Target (as a percent)	0.00%
High Yield \| Minimum
Employee benefits plans
Target (as a percent)	0.00%
High Yield \| Maximum
Employee benefits plans
Target (as a percent)	5.00%

Represents the period of operating history and sufficient trading volume of invested entity.

No definition available.

Name:	hhs_DefinedBenefitPlanPeriodOfOperatingHistoryAndSufficientTradingVolumeOfInvestedEntity
Namespace Prefix:	hhs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the defined benefit plan period required to meet investment policy's goal.

+ References

No definition available.

+ Details

Name:	hhs_DefinedBenefitPlanPeriodToMeetGoals
Namespace Prefix:	hhs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesUsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesUsLargeCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesUsMidCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesUsSmallCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=hhs_DefinedBenefitPlanEquitySecuritiesInternationalDevelopedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=hhs_DefinedBenefitPlanEquitySecuritiesEmergingMarketsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesNonUsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=hhs_DefinedBenefitPlanEquitySecuritiesInternationalDevelopedBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=hhs_DefinedBenefitPlanEquitySecuritiesHighYieldMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: