Basis of Presentation - Other Loss, net (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jul. 31, 2020 USD ($) installment
Debt Instrument [Line Items]
Loss on deconsolidation				$ 4,064	$ 0
Other nonoperating income				65
Other (loss) income, net	$ (152)		$ 549	(3,654)	549
Other income (loss)			649
Amount of grant received			1,000
Other nonoperating expense			100
Grant liability			$ 351		$ 351	$ 324
Grant liability, number of installments | installment						4
Grant liability, installment payments						$ 81
Hill International Brasil S.A.
Debt Instrument [Line Items]
Loss on deconsolidation				$ 4,064
Secured Debt
Debt Instrument [Line Items]
Other (loss) income, net		$ 345