Goodwill and Other Intangible Assets - Changes in Carrying Amounts of Goodwill by Segment (Details) $ in Thousands	6 Months Ended
Jun. 30, 2021 USD ($)
Changes in carrying amounts of goodwill
Balance at December 31, 2020	$ 902,074
Goodwill, Other Increase (Decrease)	1,232
Foreign currency translation	39
Balance at June 30, 2021	903,345
Harsco Environmental Segment
Changes in carrying amounts of goodwill
Balance at December 31, 2020	406,401
Goodwill, Other Increase (Decrease)	0
Foreign currency translation	39
Balance at June 30, 2021	406,440
Harsco Clean Earth Segment
Changes in carrying amounts of goodwill
Balance at December 31, 2020	482,647
Goodwill, Other Increase (Decrease)	1,232
Foreign currency translation	0
Balance at June 30, 2021	483,879
Harsco Rail Segment
Changes in carrying amounts of goodwill
Balance at December 31, 2020	13,026
Goodwill, Other Increase (Decrease)	0
Foreign currency translation	0
Balance at June 30, 2021	$ 13,026

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=120320667&loc=SL49117168-202975

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 350
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-Section 50
-Paragraph 1
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Amount of increase (decrease), classified as other, of an asset representing the future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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