Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Total contract assets	$ 31,200	$ 12,100
Revenue recognized in excess of amounts reclassified to trade accounts receivable, net	60,300	67,100
Contract with Customer, Liability, Revenue Recognized	67,000
Contract with Customer, Performance Obligation Satisfied in Previous Period	1,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	1,503,742	1,347,672	$ 1,307,470
Harsco Environmental | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	43,500
Harsco Environmental | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	35,000
Harsco Environmental | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	33,800
Harsco Environmental | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	20,400
Harsco Environmental | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	152,500
Harsco Rail | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	75,900
Harsco Rail | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	83,000
Harsco Rail | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	74,300
Harsco Rail | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	52,500
Harsco Rail | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	296,200
Waste Processing and Reuse Solutions [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	169,522	0	0
Railway Contracting Services [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	21,156	27,727	39,537
After-market Parts and Services; Safety and Diagnostic Technology [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	132,249	139,020	110,195
Aluminum Dross and Scrap Processing Systems [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	25,276	15,050	0
Railway Track Maintenance Equipment [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	145,968	112,547	146,267
General Corporate
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	74	143
Environmental services related to resource recovery for metals manufacturing; and related logistical services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	881,696	924,766	890,371
Applied Products [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	127,875	128,488	120,957
Operating Segments [Member] | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues		0	0
Operating Segments [Member] | Clean Earth
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	169,522	0	0
Operating Segments [Member] | Harsco Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	299,373	279,294	295,999
Operating Segments [Member] | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	1,034,847	1,068,304	1,011,328
Operating Segments [Member] | Waste Processing and Reuse Solutions [Domain] | Clean Earth
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	169,522	0	0
Operating Segments [Member] | Waste Processing and Reuse Solutions [Domain] | Harsco Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Waste Processing and Reuse Solutions [Domain] | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Railway Contracting Services [Domain] | Clean Earth
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Railway Contracting Services [Domain] | Harsco Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	21,156	27,727	39,537
Operating Segments [Member] | Railway Contracting Services [Domain] | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | After-market Parts and Services; Safety and Diagnostic Technology [Domain] | Clean Earth
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | After-market Parts and Services; Safety and Diagnostic Technology [Domain] | Harsco Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	132,249	139,020	110,195
Operating Segments [Member] | After-market Parts and Services; Safety and Diagnostic Technology [Domain] | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Aluminum Dross and Scrap Processing Systems [Domain] | Clean Earth
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Aluminum Dross and Scrap Processing Systems [Domain] | Harsco Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Aluminum Dross and Scrap Processing Systems [Domain] | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	25,276	15,050	0
Operating Segments [Member] | Railway Track Maintenance Equipment [Domain] | Clean Earth
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Railway Track Maintenance Equipment [Domain] | Harsco Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	145,968	112,547	146,267
Operating Segments [Member] | Railway Track Maintenance Equipment [Domain] | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | General Corporate | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Environmental services related to resource recovery for metals manufacturing; and related logistical services | Clean Earth
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Environmental services related to resource recovery for metals manufacturing; and related logistical services | Harsco Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Environmental services related to resource recovery for metals manufacturing; and related logistical services | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	881,696	924,766	890,371
Operating Segments [Member] | Applied Products [Domain] | Clean Earth
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Applied Products [Domain] | Harsco Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Operating Segments [Member] | Applied Products [Domain] | Harsco Environmental
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	127,875	128,488	120,957
Corporate
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	74	143
Corporate | Waste Processing and Reuse Solutions [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Corporate | Railway Contracting Services [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Corporate | After-market Parts and Services; Safety and Diagnostic Technology [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Corporate | Aluminum Dross and Scrap Processing Systems [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Corporate | Railway Track Maintenance Equipment [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Corporate | General Corporate
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	74	143
Corporate | Environmental services related to resource recovery for metals manufacturing; and related logistical services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	0	0	0
Corporate | Applied Products [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Product revenues	$ 0	$ 0	$ 0