Acquisitions and Dispositions - Preliminary Valuation of Identifiable Intangible Assets and Amortization Periods (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Apr. 06, 2020	Jun. 28, 2019	Jun. 30, 2020	Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount					$ 517,059	$ 412,657
Permits
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount					308,559	170,322
Noncompete Agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount					2,500	0
Air rights
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount					26,139	26,139
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount					31,698	$ 31,719
ESOL | Permits
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	22 years
Preliminary Valuation	$ 138,000				138,000
ESOL | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	10 years
Preliminary Valuation	$ 23,000				23,000
ESOL | Noncompete Agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	4 years
Harsco Clean Earth Segment
Acquired Finite-Lived Intangible Assets [Line Items]
Preliminary Valuation		$ 261,100			242,200
Harsco Clean Earth Segment | Permits
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period		18 years
Preliminary Valuation		$ 176,100			170,100
Harsco Clean Earth Segment | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period		8 years
Preliminary Valuation		$ 33,400			20,500
Harsco Clean Earth Segment | Air rights
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period		27 years
Preliminary Valuation		$ 25,600			25,600
Harsco Clean Earth Segment | Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period		12 years
Preliminary Valuation		$ 26,000			26,000
Harsco Clean Earth Segment
Measurement Period Adjustments
Permits and rights				$ (6,000)
Customer relationships				(12,900)
Intangible assets				(18,900)
Air rights				0
Trade names				0
Harsco Clean Earth Segment | ESOL
Acquired Finite-Lived Intangible Assets [Line Items]
Preliminary Valuation	$ 161,000				161,000
Gross Carrying Amount	2,500				2,500
Total identifiable intangible assets acquired	$ 163,500				$ 163,500
Measurement Period Adjustments
Intangible assets			$ 0
Harsco Clean Earth Segment | ESOL | Noncompete Agreements
Measurement Period Adjustments
Permits and rights			0
Customer relationships			0
Intangible assets			0
Total identifiable intangible assets acquired			$ 0
Harsco Clean Earth Segment | Harsco Clean Earth Segment
Acquired Finite-Lived Intangible Assets [Line Items]
Preliminary Valuation		$ 261,100
Measurement Period Adjustments
Intangible assets				$ (18,900)