Leases - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Apr. 06, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating And Finance Leases, Excluding Short Term Leases, Renewal Option	10 years
Weighted average remaining lease term - Operating leases (in years)	8 years 1 month 6 days		11 years 6 months 25 days
Operating And Finance Leases, Excluding Short Term Leases, Termination Option	1 year
Anticipated Lease Commencements	$ 4.6
ESOL | Harsco Clean Earth Segment
Lessee, Lease, Description [Line Items]
Right-of-use assets	$ 56.0	$ 56.0
Minimum
Lessee, Lease, Description [Line Items]
Operating And Finance Leases, Excluding Short Term Leases, Weighted-Average Remaining Lease Term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Operating And Finance Leases, Excluding Short Term Leases, Weighted-Average Remaining Lease Term	30 years