Basis of Presentation - Earnings (Loss) per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net (loss) earnings	$ (703)	$ 1,317	$ 86	$ (1,659)
Less: net (loss) earnings - noncontrolling interests	(14)	58	(112)	265
Net (loss) earnings attributable to Hill International, Inc.	$ (689)	$ 1,259	$ 198	$ (1,924)
Basic weighted average common shares outstanding (in shares)	58,073	57,245	57,858	57,102
Effect of dilutive securities:
Diluted weighted average common shares outstanding (in shares)	58,073	57,245	59,767	57,102
Basic (loss) earnings per common share - Hill International, Inc. (in dollars per share)	$ (0.01)	$ 0.02	$ 0	$ (0.03)
Diluted (loss) earnings per common share - Hill International, Inc. (in dollars per share)	$ (0.01)	$ 0.02	$ 0	$ (0.03)
Stock options
Effect of dilutive securities:
Dilutive securities (in shares)	0	0	0	0
Unissued share-based compensation units
Effect of dilutive securities:
Dilutive securities (in shares)	0	0	1,909	0