| Cover | Apr. 26, 2021 |
| Cover [Abstract] | |
| City Area Code | 312 |
| Local Phone Number | 496-1200 |
| Document Type | 8-K |
| Entity File Number | 0-25837 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 36-2681268 |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Trading Symbol | HSII |
| Security Exchange Name | NASDAQ |
| Entity Registrant Name | HEIDRICK & STRUGGLES INTERNATIONAL, INC. |
| Written Communications | false |
| Soliciting Material | false |
| Entity Address, Postal Zip Code | 60606-6303 |
| Entity Central Index Key | 0001066605 |
| Document Period End Date | Apr. 26, 2021 |
| Entity Address, Address Line One | 233 South Wacker Drive |
| Entity Address, Address Line Two | Suite 4900 |
| Entity Address, City or Town | Chicago |
| Entity Address, State or Province | IL |
| Amendment Flag | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
