Revenue Recognition - Revenues by Primary Geographical Markets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 398,841	$ 329,902
Waste Processing and Reuse Solutions [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	78,812	0
Environmental services related to resource recovery for metals manufacturing and related logistical services
Disaggregation of Revenue [Line Items]
Total revenues	207,346	224,061
Applied Products [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	30,262	30,390
Aluminum Dross and Scrap Processing Systems [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	3,951	6,861
Railway Track Maintenance Equipment [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	42,615	33,608
After-market Parts and Services; Safety and Diagnostic Technology [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	31,200	31,301
Railway Contracting Services [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	4,655	3,681
North America
Disaggregation of Revenue [Line Items]
Total revenues	202,466	123,714
Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	114,481	108,234
Latin America
Disaggregation of Revenue [Line Items]
Total revenues	33,925	37,582
Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	27,864	41,759
Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	15,889	13,915
Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	4,216	4,698
Operating Segments | Harsco Environmental Segment
Disaggregation of Revenue [Line Items]
Total revenues	241,559	261,312
Operating Segments | Harsco Environmental Segment | Waste Processing and Reuse Solutions [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Environmental Segment | Environmental services related to resource recovery for metals manufacturing and related logistical services
Disaggregation of Revenue [Line Items]
Total revenues	207,346	224,061
Operating Segments | Harsco Environmental Segment | Applied Products [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	30,262	30,390
Operating Segments | Harsco Environmental Segment | Aluminum Dross and Scrap Processing Systems [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	3,951	6,861
Operating Segments | Harsco Environmental Segment | Railway Track Maintenance Equipment [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Environmental Segment | After-market Parts and Services; Safety and Diagnostic Technology [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Environmental Segment | Railway Contracting Services [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Environmental Segment | North America
Disaggregation of Revenue [Line Items]
Total revenues	69,881	73,349
Operating Segments | Harsco Environmental Segment | Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	96,317	98,221
Operating Segments | Harsco Environmental Segment | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	33,260	36,991
Operating Segments | Harsco Environmental Segment | Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	21,996	34,138
Operating Segments | Harsco Environmental Segment | Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	15,889	13,915
Operating Segments | Harsco Environmental Segment | Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	4,216	4,698
Operating Segments | Harsco Clean Earth Segment
Disaggregation of Revenue [Line Items]
Total revenues	78,812	0
Operating Segments | Harsco Clean Earth Segment | Waste Processing and Reuse Solutions [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	78,812	0
Operating Segments | Harsco Clean Earth Segment | Environmental services related to resource recovery for metals manufacturing and related logistical services
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | Applied Products [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | Aluminum Dross and Scrap Processing Systems [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | Railway Track Maintenance Equipment [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | After-market Parts and Services; Safety and Diagnostic Technology [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | Railway Contracting Services [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | North America
Disaggregation of Revenue [Line Items]
Total revenues	78,812	0
Operating Segments | Harsco Clean Earth Segment | Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Clean Earth Segment | Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Rail Segment
Disaggregation of Revenue [Line Items]
Total revenues	78,470	68,590
Operating Segments | Harsco Rail Segment | Waste Processing and Reuse Solutions [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Rail Segment | Environmental services related to resource recovery for metals manufacturing and related logistical services
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Rail Segment | Applied Products [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Rail Segment | Aluminum Dross and Scrap Processing Systems [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Rail Segment | Railway Track Maintenance Equipment [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	42,615	33,608
Operating Segments | Harsco Rail Segment | After-market Parts and Services; Safety and Diagnostic Technology [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	31,200	31,301
Operating Segments | Harsco Rail Segment | Railway Contracting Services [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	4,655	3,681
Operating Segments | Harsco Rail Segment | North America
Disaggregation of Revenue [Line Items]
Total revenues	53,773	50,365
Operating Segments | Harsco Rail Segment | Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	18,164	10,013
Operating Segments | Harsco Rail Segment | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	665	591
Operating Segments | Harsco Rail Segment | Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	5,868	7,621
Operating Segments | Harsco Rail Segment | Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Harsco Rail Segment | Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Waste Processing and Reuse Solutions [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Environmental services related to resource recovery for metals manufacturing and related logistical services
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Applied Products [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Aluminum Dross and Scrap Processing Systems [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Railway Track Maintenance Equipment [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | After-market Parts and Services; Safety and Diagnostic Technology [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Railway Contracting Services [Domain]
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | North America
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Corporate | Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0