XML 80 R65.htm IDEA: XBRL DOCUMENT
v3.25.1

Employee Benefit Plans - Plan Assets (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | $ 30,119 | $ 103,696 | $ 103,891
Total plan assets, percentage | 100.00% | 100.00% |
Equity securities |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | $ 23,658 | $ 20,635 |
Total plan assets, percentage | 79.00% | 20.00% |
Debt securities |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | $ 5,252 | $ 76,036 |
Total plan assets, percentage | 17.00% | 73.00% |
Other |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | $ 1,209 | $ 7,025 |
Total plan assets, percentage | 4.00% | 7.00% |
Total investments, excluding investments valued at NAV |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | $ 28,910 | $ 96,671 |
Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 27,327 | 87,482 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 23,658 | 20,635 |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Debt securities |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 3,669 | 66,847 |
Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 1,583 | 9,189 |
Significant Other Observable Inputs (Level 2) | Equity securities |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 0 | 0 |
Significant Other Observable Inputs (Level 2) | Debt securities |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 1,583 | 9,189 |
Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Equity securities |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 0 | 0 |
Significant Unobservable Inputs (Level 3) | Debt securities |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | 0 | 0 |
Investments valued at NAV |  |  |
Defined Benefit Plan, Plan Assets, Allocation [Line Items] |  |  |
Total plan assets, amount | $ 1,209 | $ 7,025 |

X
- Definition Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- 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 Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsAllocationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of actual 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/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanDebtSecurityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=hrth_DefinedBenefitPlanOtherSecuritiesInvestmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel12And3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |