Acquisitions and Dispositions - Acquisitions Narrative (Details) - USD ($)			3 Months Ended
	Apr. 06, 2020	Jun. 28, 2019	Mar. 31, 2021	Mar. 31, 2020	Jan. 31, 2020	Jan. 01, 2020
Business Acquisition [Line Items]
Total revenues			$ 528,855,000	$ 398,841,000
Operating income from continuing operations			24,824,000	2,881,000
Additional interest expense			16,864,000	12,649,000
Receivable with Imputed Interest, Face Amount			40,000,000.0
Receivables, Fair Value Disclosure			36,200,000		$ 34,300,000	$ 34,300,000
Gain on sale of discontinued business			0	18,462,000
Stericycle
Business Acquisition [Line Items]
Corporate charge				8,900,000
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
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			134,200,000
Operating income from continuing operations			$ 7,000,000.0
Harsco Clean Earth Segment
Business Acquisition [Line Items]
Percentage of interests acquired		100.00%
Cash consideration		$ 628,000,000
Business Acquisition, Purchased Enterprise Valuation		$ 625,000,000
Clean Earth and ESOL
Business Acquisition [Line Items]
Additional interest expense				$ 4,700,000