XML 68 R55.htm IDEA: XBRL DOCUMENT
v3.24.3

Financial Instruments and Fair Value - Schedule of Fair Value, Separate Account Investment (Details) - USD ($) $ in Thousands | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total | $ 57,049 | $ 45,265
Other Current Assets |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total | 1,300 | 1,289
Assets Designated for Retirement and Pension Plans |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total | 11,203 | 11,105
Investments |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total | 59,089 | 47,287
Other Current Liabilities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total | (1,300) | (1,289)
Retirement and Pension Plans |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total | (13,243) | (13,127)
Fair Value, Inputs, Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
U.S. non-qualified deferred compensation plan | 59,089 | 47,287
Fair Value, Inputs, Level 1 | Other Current Assets |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
U.S. non-qualified deferred compensation plan | 0 | 0
Fair Value, Inputs, Level 1 | Assets Designated for Retirement and Pension Plans |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
U.S. non-qualified deferred compensation plan | 0 | 0
Fair Value, Inputs, Level 1 | Investments |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
U.S. non-qualified deferred compensation plan | 59,089 | 47,287
Fair Value, Inputs, Level 1 | Other Current Liabilities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
U.S. non-qualified deferred compensation plan | 0 | 0
Fair Value, Inputs, Level 1 | Retirement and Pension Plans |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
U.S. non-qualified deferred compensation plan | 0 | 0
Fair Value, Inputs, Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Retirement and pension plan assets | 12,503 | 12,394
Pension benefit obligation | (14,543) | (14,416)
Total | (2,040) | (2,022)
Fair Value, Inputs, Level 2 | Other Current Assets |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Retirement and pension plan assets | 1,300 | 1,289
Pension benefit obligation | 0 | 0
Total | 1,300 | 1,289
Fair Value, Inputs, Level 2 | Assets Designated for Retirement and Pension Plans |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Retirement and pension plan assets | 11,203 | 11,105
Pension benefit obligation | 0 | 0
Total | 11,203 | 11,105
Fair Value, Inputs, Level 2 | Investments |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Retirement and pension plan assets | 0 | 0
Pension benefit obligation | 0 | 0
Total | 0 | 0
Fair Value, Inputs, Level 2 | Other Current Liabilities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Retirement and pension plan assets | 0 | 0
Pension benefit obligation | (1,300) | (1,289)
Total | (1,300) | (1,289)
Fair Value, Inputs, Level 2 | Retirement and Pension Plans |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Retirement and pension plan assets | 0 | 0
Pension benefit obligation | (13,243) | (13,127)
Total | $ (13,243) | $ (13,127)

X
- Definition Carrying amount as of the balance sheet date of assets held under deferred compensation agreements. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(17)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_DeferredCompensationPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanBenefitObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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 No definition available. + Details
Name: | us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of asset after deduction of liability. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_FairValueNetAssetLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=hsii_AssetsDesignatedForRetirementAndPensionPlansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_InvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentLiabilitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_PensionPlansDefinedBenefitMember
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: |