| Cover | Aug. 09, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 9, 2021 |
| Entity Registrant Name | HILL INTERNATIONAL, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-33961 |
| Entity Tax Identification Number | 20-0953973 |
| Entity Address, Address Line One | One Commerce Square |
| Entity Address, Address Line Two | 2005 Market Street, 17th Floor |
| Entity Address, City or Town | Philadelphia |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19103 |
| City Area Code | 215 |
| Local Phone Number | 309-7700 |
| Title of 12(b) Security | Common Stock, par value $0.0001 |
| Trading Symbol | HIL |
| Security Exchange Name | NYSE |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001287808 |
