Information by Segment and Geographic Area (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) Customer segment	Dec. 31, 2019 USD ($) Customer	Dec. 31, 2018 USD ($) Customer
Revenue, Major Customer [Line Items]
Revenues | $	$ 1,863,864	$ 1,503,742	$ 1,347,672
Number of reportable segments | segment	3
Number of major customers | Customer	1
Harsco Environmental
Revenue, Major Customer [Line Items]
Number of major customers | Customer	1	1	1
Clean Earth
Revenue, Major Customer [Line Items]
Number of major customers | Customer	1	0
Harsco Rail
Revenue, Major Customer [Line Items]
Number of major customers | Customer	1	1	1
All Other
Revenue, Major Customer [Line Items]
Revenues | $	$ 677,358	$ 718,663	$ 745,943
U.S. Plans
Revenue, Major Customer [Line Items]
Revenues | $	1,048,059	640,390	458,383
United Kingdom
Revenue, Major Customer [Line Items]
Revenues | $	$ 138,447	$ 144,689	$ 143,346