Acquisitions and Dispositions - Acquisitions Narrative (Details) - USD ($)			1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 06, 2020	Jun. 28, 2019	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2020
Business Acquisition [Line Items]
Total revenues				$ 509,398,000	$ 423,155,000	$ 1,355,520,000	$ 1,103,955,000
Operating income from continuing operations				5,064,000	46,745,000	9,813,000	84,368,000	$ 84,368,000
Additional interest expense				15,794,000	12,819,000	43,396,000	24,429,000
Receivable with Imputed Interest, Face Amount				40,000,000.0		40,000,000.0
Receivables, Fair Value Disclosure			$ 34,300,000	35,600,000		35,600,000			$ 34,300,000
Gain on sale of discontinued business			18,400,000	0	527,980,000	18,371,000	527,980,000
Stericycle
Business Acquisition [Line Items]
Corporate charge					8,600,000	8,900,000	26,500,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Harsco Industrial IKG
Business Acquisition [Line Items]
Selling price									$ 85,000,000.0
Receivable with Imputed Interest, Face Amount			40,000,000.0
Disposal Group, Net Gain on Disposal			$ 9,000,000
Discontinued Operations, Held-for-sale | Harsco Industrial
Business Acquisition [Line Items]
Gain on sale of discontinued business				0	527,980,000	18,371,000	527,980,000
Corporate overhead expenses					700,000		3,400,000
Harsco Clean Earth Segment
Business Acquisition [Line Items]
Percentage of interests acquired		100.00%
Cash consideration		$ 628,000,000
Goodwill to be deductible for income tax purposes		16,300,000
Direct acquisition costs					2,000,000.0		14,500,000
Enterprise valuation		625,000,000
Estimated reimbursements		$ 11,000,000
ESOL
Business Acquisition [Line Items]
Percentage of interests acquired	100.00%
Cash consideration	$ 429,000,000.0
Goodwill to be deductible for income tax purposes	$ 36,800,000
Total revenues						236,700,000
Operating income from continuing operations						4,700,000
Direct acquisition costs				$ 10,600,000		41,000,000.0
Clean Earth and ESOL
Business Acquisition [Line Items]
Additional interest expense					$ 5,600,000	$ 4,700,000	$ 34,900,000