Notes Payable and Long-Term Debt - Summary of Outstanding Debt Obligations (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Total notes payable and long-term debt, gross	$ 60,334	$ 55,443
Less: unamortized discount and deferred financing costs related to Société Générale 2017 Term Loan Facility	(183)	(300)
Notes payable and long-term debt	60,151	55,143
Current portion of notes payable	31,533	26,043
Current portion of unamortized debt discount and deferred financing costs	(198)	(202)
Current maturities of notes payable and long-term debt	31,335	25,841
Notes payable and long-term debt, net of current maturities	$ 28,816	$ 29,302
Hill International, Inc. - Société Générale 2017 Term Loan Facility | Secured Debt
Debt Instrument [Line Items]
Variable interest rate	7.49%	7.51%
Total notes payable and long-term debt, gross	$ 28,425	$ 28,650
Hill International, Inc. - Société Générale Domestic Revolving Credit Facility | Secured Debt
Debt Instrument [Line Items]
Variable interest rate	5.17%	5.06%
Total notes payable and long-term debt, gross	$ 23,303	$ 19,400
Hill International N.V.. - Société Générale International Revolving Credit Facility | Secured Debt
Debt Instrument [Line Items]
Variable interest rate	4.46%	4.06%
Total notes payable and long-term debt, gross	$ 4,884	$ 5,802
Hill International, Inc. - First Abu Dhabi Bank ("FAB") PJSC Overdraft Credit Facility | Unsecured Debt
Debt Instrument [Line Items]
Variable interest rate	5.62%	5.71%
Total notes payable and long-term debt, gross	$ 2,695	$ 151
Philadelphia Industrial Development Corporation Loan | Unsecured Debt
Debt Instrument [Line Items]
Fixed interest rate	2.75%	2.79%
Total notes payable and long-term debt, gross	$ 310	$ 358
Hill International Spain S.A. - Bankinter S.A. 2020 Term Loan | Unsecured Debt
Debt Instrument [Line Items]
Variable interest rate	2.39%	2.23%
Total notes payable and long-term debt, gross	$ 143	$ 239
Hill International Spain S.A. - Banco Santander, S.A. Term Loan | Unsecured Debt
Debt Instrument [Line Items]
Fixed interest rate	3.86%	3.91%
Total notes payable and long-term debt, gross	$ 200	$ 295
Hill International Spain S.A. - BBVA, S.A. P.P. Term Loan | Unsecured Debt
Debt Instrument [Line Items]
Variable interest rate	2.25%	2.28%
Total notes payable and long-term debt, gross	$ 204	$ 300
Hill International Spain S.A. - Bankia. S.A. 2020 Term Loan | Unsecured Debt
Debt Instrument [Line Items]
Variable interest rate	2.50%	2.54%
Total notes payable and long-term debt, gross	$ 170	$ 248