Revenue Recognition - Revenues by Primary Geographical Markets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 509,398	$ 423,155	$ 1,355,520	$ 1,103,955
Waste Processing and Reuse Solutions
Disaggregation of Revenue [Line Items]
Total revenues	194,098	87,639	434,489	87,639
Environmental services related to resource recovery for metals manufacturing and related logistical services
Disaggregation of Revenue [Line Items]
Total revenues	181,640	218,788	563,159	673,244
Applied Products
Disaggregation of Revenue [Line Items]
Total revenues	38,166	34,890	95,019	98,966
Aluminum Dross and Scrap Processing Systems
Disaggregation of Revenue [Line Items]
Total revenues	2,701	7,205	9,879	19,323
Railway Track Maintenance Equipment
Disaggregation of Revenue [Line Items]
Total revenues	55,493	30,233	138,519	102,801
After-market Parts and Services; Safety and Diagnostic Technology
Disaggregation of Revenue [Line Items]
Total revenues	29,100	37,100	92,800	105,101
Railway Contracting Services
Disaggregation of Revenue [Line Items]
Total revenues	8,200	7,300	21,655	16,881
North America
Disaggregation of Revenue [Line Items]
Total revenues	315,876	222,638	793,738	489,742
Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	113,922	103,835	328,230	321,085
Latin America
Disaggregation of Revenue [Line Items]
Total revenues	29,497	35,678	89,045	110,305
Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	30,239	41,279	85,877	123,788
Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	15,558	15,302	46,240	44,959
Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	4,306	4,423	12,390	14,076
Operating Segments | Harsco Environmental Segment
Disaggregation of Revenue [Line Items]
Total revenues	222,507	260,883	668,057	791,533
Operating Segments | Harsco Environmental Segment | Waste Processing and Reuse Solutions
Disaggregation of Revenue [Line Items]
Total revenues	0	0	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	181,640	218,788	563,159	673,244
Operating Segments | Harsco Environmental Segment | Applied Products
Disaggregation of Revenue [Line Items]
Total revenues	38,166	34,890	95,019	98,966
Operating Segments | Harsco Environmental Segment | Aluminum Dross and Scrap Processing Systems
Disaggregation of Revenue [Line Items]
Total revenues	2,701	7,205	9,879	19,323
Operating Segments | Harsco Environmental Segment | Railway Track Maintenance Equipment
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Environmental Segment | After-market Parts and Services; Safety and Diagnostic Technology
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Environmental Segment | Railway Contracting Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Environmental Segment | North America
Disaggregation of Revenue [Line Items]
Total revenues	58,973	78,076	186,210	229,537
Operating Segments | Harsco Environmental Segment | Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	92,506	93,426	271,795	290,125
Operating Segments | Harsco Environmental Segment | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	29,085	35,127	87,453	108,390
Operating Segments | Harsco Environmental Segment | Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	22,079	34,529	63,969	104,446
Operating Segments | Harsco Environmental Segment | Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	15,558	15,302	46,240	44,959
Operating Segments | Harsco Environmental Segment | Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	4,306	4,423	12,390	14,076
Operating Segments | Harsco Clean Earth Segment
Disaggregation of Revenue [Line Items]
Total revenues	194,098	87,639	434,489	87,639
Operating Segments | Harsco Clean Earth Segment | Waste Processing and Reuse Solutions
Disaggregation of Revenue [Line Items]
Total revenues	194,098	87,639	434,489	87,639
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	0	0
Operating Segments | Harsco Clean Earth Segment | Applied Products
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | Aluminum Dross and Scrap Processing Systems
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | Railway Track Maintenance Equipment
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | After-market Parts and Services; Safety and Diagnostic Technology
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | Railway Contracting Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | North America
Disaggregation of Revenue [Line Items]
Total revenues	194,098	87,639	434,489	87,639
Operating Segments | Harsco Clean Earth Segment | Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Clean Earth Segment | Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Rail Segment
Disaggregation of Revenue [Line Items]
Total revenues	92,793	74,633	252,974	224,783
Operating Segments | Harsco Rail Segment | Waste Processing and Reuse Solutions
Disaggregation of Revenue [Line Items]
Total revenues	0	0	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	0	0
Operating Segments | Harsco Rail Segment | Applied Products
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Rail Segment | Aluminum Dross and Scrap Processing Systems
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Rail Segment | Railway Track Maintenance Equipment
Disaggregation of Revenue [Line Items]
Total revenues	55,493	30,233	138,519	102,801
Operating Segments | Harsco Rail Segment | After-market Parts and Services; Safety and Diagnostic Technology
Disaggregation of Revenue [Line Items]
Total revenues	29,100	37,100	92,800	105,101
Operating Segments | Harsco Rail Segment | Railway Contracting Services
Disaggregation of Revenue [Line Items]
Total revenues	8,200	7,300	21,655	16,881
Operating Segments | Harsco Rail Segment | North America
Disaggregation of Revenue [Line Items]
Total revenues	62,805	56,923	173,039	172,566
Operating Segments | Harsco Rail Segment | Western Europe
Disaggregation of Revenue [Line Items]
Total revenues	21,416	10,409	56,435	30,960
Operating Segments | Harsco Rail Segment | Latin America
Disaggregation of Revenue [Line Items]
Total revenues	412	551	1,592	1,915
Operating Segments | Harsco Rail Segment | Asia-Pacific
Disaggregation of Revenue [Line Items]
Total revenues	8,160	6,750	21,908	19,342
Operating Segments | Harsco Rail Segment | Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Harsco Rail Segment | Eastern Europe
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 0	$ 0