Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total contract assets	$ 91,900		$ 97,200
Total advances on contracts	9,800		$ 23,900
Revenue recognized	$ 17,600	$ 10,700
SBB
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percentage complete	91.00%
(Decrease) to loss on contracts	$ 1,100
Network Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Provisions recognized	$ (1,100)
Deutsche Bahn
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percentage complete	49.00%
Provisions recognized	$ (13,300)
Contract | Network Rail
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percentage complete	68.00%
Harsco Environmental Segment
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 60,821
Harsco Environmental Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	17,632
Harsco Environmental Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	15,092
Harsco Environmental Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	12,435
Harsco Environmental Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	9,398
Harsco Environmental Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2029-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	3,132
Harsco Environmental Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2030-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	3,132
Harsco Rail Segment
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	97,177
Harsco Rail Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	44,680
Harsco Rail Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	22,231
Harsco Rail Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	20,615
Harsco Rail Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	4,897
Harsco Rail Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2029-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	4,031
Harsco Rail Segment | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2030-03-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 723