Acquisitions and Dispositions - Narrative (Details) $ in Thousands, £ in Millions			1 Months Ended				12 Months Ended
	Apr. 06, 2020 USD ($)	Jun. 28, 2019 USD ($)	Jan. 31, 2020 USD ($)	Nov. 30, 2019 USD ($)	May 31, 2018 USD ($)	May 31, 2018 GBP (£)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jul. 01, 2019 USD ($)	May 31, 2018 GBP (£)
Business Acquisition [Line Items]
Product revenues							$ 1,863,864	$ 1,503,742	$ 1,347,672
Operating income from continuing operations							21,081	104,279	130,695
Interest Expense							59,689	36,586	21,531
Purchase of businesses, net of cash acquired							432,855	623,495	56,389
Proceeds from sale of businesses							37,219	658,414	0
Receivable with Imputed Interest, Face Amount			$ 40,000
Receivables, Fair Value Disclosure			34,300				36,900
Income (loss) from discontinued businesses							18,281	569,135	0
Clean Earth
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Purchase price		$ 628,000
Business Combination, Additional Expense Related To Reimbursement of NOL							2,300
Business Combination, Additional Expense Related To Reimbursement of NOL, Fair Value							11,000
Tax deductible Goodwill		16,300
Costs associated with the acquisition								15,200
Business Combination, Consideration Transferred		$ 625,000
Business Combination, Contingent Consideration Arrangements, Post-Closing Period		5 years
Altek
Business Acquisition [Line Items]
Purchase price					$ 57,400
Estimated preliminary fair value					12,100
Purchase of businesses, net of cash acquired					60,000	£ 45
Additional contingent consideration					$ 33,000						£ 25
ESOL
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Purchase price	$ 429,000
Tax deductible Goodwill	$ 36,800
Product revenues							368,000
Operating income from continuing operations							7,400
Costs associated with the acquisition							49,000	7,300
Harsco Industrial | Discontinued Operations, Held-for-sale [Member]
Business Acquisition [Line Items]
Disposal Group, Including Discontinued Operation, Corporate Overhead								4,000	5,600
Income (loss) from discontinued businesses							18,281	569,135	$ 0
Harsco Industrial Patterson-Kelley [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal Group, Net Gain on Disposal, After Tax				$ 33,000
Disposal Group, Net Gain on Disposal, Before Tax				41,200
Proceeds from sale of businesses				$ 60,000
Harsco Industrial IKG | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal Group, Including Discontinued Operation, Consideration			85,000
Disposal Group, Net Gain on Disposal, After Tax			9,000
Receivable with Imputed Interest, Face Amount			40,000
Receivables, Fair Value Disclosure			34,300
Income (loss) from discontinued businesses			$ 18,400
Harsco Industrial Air-X-Changers Business [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Disposal Group, Including Discontinued Operation, Consideration										$ 600,000
Disposal Group, Net Gain on Disposal, After Tax										421,000
Disposal Group, Net Gain on Disposal, Before Tax										$ 527,900
Acquisition-related Costs [Member] | Clean Earth
Business Acquisition [Line Items]
Interest Expense							$ 4,700	$ 39,900