Other Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net gains	$ (3,723)	$ (6,303)	$ (3,868)
Employee termination benefit costs	10,888	6,619	4,763
Costs to exit activities	693	4,208	170
Impaired asset write-downs	776	773	104
Contingent Consideration Adjustments	(2,386)	7,681	2,939
Other expense	(226)	(237)	(431)
Total	10,794	(2,621)	(2,201)
Corporate
Segment Reporting Information [Line Items]
Net gains	0	0	(1,218)
Employee termination benefit costs	27	1,012	1,206
Costs to exit activities	29	196	(182)
Contingent Consideration Adjustments	2,274	0	0
Clean Earth
Segment Reporting Information [Line Items]
Employee termination benefit costs	833	1,960	0
Contingent Consideration Adjustments	112	(825)	0
Harsco Rail
Segment Reporting Information [Line Items]
Employee termination benefit costs	639	2,393	704
Costs to exit activities	160	3,042	0
Impaired asset write-downs	0	141	0
Harsco Environmental
Segment Reporting Information [Line Items]
Net gains	(3,723)	(6,303)	(2,650)
Employee termination benefit costs	9,389	1,254	2,853
Costs to exit activities	504	970	352
Impaired asset write-downs	776	632	104
Contingent Consideration Adjustments	$ 0	$ (8,506)	$ 2,939