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Financial Instruments and Fair Value - Narrative (Details) - USD ($) | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Jun. 30, 2023 | Dec. 31, 2023 | Dec. 31, 2022
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Aggregate cost basis for investments |  | $ 37,200,000 | $ 29,100,000
Earnout accruals |  | 0 | 36,010,000
Earnout liability |  | 38,601,000 | 0
Impairment |  | 7,246,000 |
Heidrick Consulting Reporting Units |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Impairment | $ 7,200,000 | 7,200,000 |
Fair Value, Inputs, Level 3 | Current and Other Current Liabilities | Acqusition Earnout Accruals |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Earnout accruals |  | 0 | 36,000,000
Fair Value, Inputs, Level 3 | Non-Current and Other Non-Current Liabilities | Acqusition Earnout Accruals |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Earnout liability |  | 38,600,000 | 0
Fair Value, Inputs, Level 3 | Current Accrued Salaries and Benefits | Contingent Compensation |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Earnout accruals |  | 6,000,000 | 1,500,000
Fair Value, Inputs, Level 3 | Non-Current Accrued Salaries and Benefits | Contingent Compensation |  |  |
Fair Value, Option, Quantitative Disclosures [Line Items] |  |  |
Earnout liability |  | $ 12,900,000 | $ 6,700,000

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