Acquisitions and Dispositions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Apr. 06, 2020	Dec. 31, 2019	Jun. 28, 2019
Business Acquisition [Line Items]
Goodwill	$ 881,665	$ 881,665		$ 738,369
Gross Carrying Amount	574,570	574,570		412,657
Noncompete Agreements
Business Acquisition [Line Items]
Gross Carrying Amount	2,500	2,500		0
Harsco Clean Earth Segment
Business Acquisition [Line Items]
Cash and cash equivalents	3,600	3,600
Trade accounts receivable, net	62,500	62,500
Other receivables	2,100	2,100
Other current assets	7,300	7,300
Property, plant and equipment	77,000	77,000
Right-of-use assets	25,800	25,800
Goodwill	330,600	330,600
Intangible assets	242,200	242,200			$ 261,100
Other assets	1,200	1,200
Accounts payable	(23,100)	(23,100)
Other current liabilities	(19,700)	(19,700)
Deferred income taxes	(45,700)	(45,700)
Operating lease liabilities	(19,500)	(19,500)
Total identifiable net assets of Clean Earth	635,700	635,700			635,900
Acquisition consideration payable (b)	0	0
Other liabilities	(8,600)	(8,600)
Harsco Clean Earth Segment
Business Acquisition [Line Items]
Goodwill	482,530	482,530		$ 330,230
Measurement Period Adjustments
Intangible assets		(18,900)
Total identifiable intangible assets of Clean Earth		200
Harsco Clean Earth Segment | ESOL
Business Acquisition [Line Items]
Cash and cash equivalents	400	400	$ 400
Trade accounts receivable, net	124,100	124,100	124,100
Inventory	5,000	5,000	5,000
Other current assets	700	700	700
Property, plant and equipment	105,300	105,300	105,300
Right-of-use assets	56,000	56,000	56,000
Goodwill	152,000	152,000	152,000
Intangible assets	161,000	161,000	161,000
Other assets	200	200	200
Accounts payable	48,600	48,600	48,600
Accrued expenses	(17,500)	(17,500)	(17,500)
Current portion of operating lease liabilities	(16,600)	(16,600)	(16,600)
Other current liabilities	6,400	6,400	6,400
Environmental liabilities	(24,400)	(24,400)	(24,400)
Deferred income taxes	(15,500)	(15,500)	15,500
Operating lease liabilities	39,400	39,400	39,400
Total identifiable net assets of Clean Earth	436,300	436,300	436,300
Gross Carrying Amount	2,500	2,500	2,500
Business Acquisitions, Purchase Price Allocation	438,800	438,800	$ 438,800
Measurement Period Adjustments
Cash and cash equivalents	0
Trade accounts receivable	0
Inventory	0
Other current assets	0
Property, plant and equipment	0
Right-of-use assets	0
Goodwill	0
Intangible assets	0
Other assets	0
Accounts payable	0
Current portion of operating lease liabilities	0
Current portion of operating lease liabilities	0
Other current liabilities	0
Environmental liabilities	0
Deferred income taxes	0
Operating lease liabilities	0
Total identifiable intangible assets of Clean Earth	0
Total identifiable net assets of ESOL	0
Harsco Clean Earth Segment | ESOL | Noncompete Agreements
Measurement Period Adjustments
Intangible assets	$ 0
Harsco Clean Earth Segment | Harsco Clean Earth Segment
Business Acquisition [Line Items]
Cash and cash equivalents					42,800
Trade accounts receivable, net					63,700
Other receivables					800
Other current assets					8,700
Property, plant and equipment					75,600
Right-of-use assets					14,400
Goodwill					313,800
Intangible assets					261,100
Other assets					4,000
Accounts payable					(23,000)
Other current liabilities					(18,000)
Deferred income taxes					(51,200)
Operating lease liabilities					(11,100)
Acquisition consideration payable (b)					(39,200)
Other liabilities					$ (6,500)
Measurement Period Adjustments
Cash and cash equivalents		(39,200)
Trade accounts receivable		(1,200)
Other current assets		(1,400)
Property, plant and equipment		1,400
Right-of-use assets		11,400
Goodwill		16,800
Intangible assets		(18,900)
Other assets		(2,800)
Accounts payable		(100)
Other current liabilities		(1,700)
Deferred income taxes		5,500
Operating lease liabilities		(8,400)
Other receivables		1,300
Acquisition consideration payable (b)		39,200
Other liabilities		$ (2,100)