Acquisitions and Dispositions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Jun. 28, 2019	Dec. 31, 2018	Jun. 30, 2018
Business Acquisition [Line Items]
Goodwill	$ 725,106			$ 404,713
Harsco Clean Earth Segment
Business Acquisition [Line Items]
Cash and cash equivalents	3,600		$ 42,800
Trade accounts receivable, net	63,200		63,700
Other receivables	2,100		800
Other current assets	7,300		8,700
Property, plant and equipment	77,800		75,600
Right-of-use assets	21,300		14,400
Goodwill	328,200		313,800
Intangible assets	242,200		261,100
Other assets	1,000		4,000
Accounts payable	(23,000)		(23,000)
Acquisition consideration payable	0		(39,200)
Other current liabilities	(19,500)		(18,000)
Net deferred taxes liabilities	(46,700)		(51,200)
Operating lease liabilities	(15,100)		(11,100)
Other liabilities	(6,800)		(6,500)
Total identifiable net assets of Altek	635,600		635,900
Acquisition consideration payable			$ (2,800)
Altek
Business Acquisition [Line Items]
Cash and cash equivalents		$ 1,700			$ 1,700
Net working capital		(1,300)			(1,500)
Property, plant and equipment		3,300			3,300
Goodwill		22,500			20,900
Intangible assets		52,700			52,500
Net deferred taxes liabilities		(8,500)			(8,500)
Other liabilities		(300)			(300)
Total identifiable net assets of Altek		70,100			$ 68,100
Measurement Period Adjustments
Net working capital		200
Intangible assets		200
Goodwill		1,600
Total identifiable net assets of Altek		$ 2,000
Harsco Clean Earth Segment
Business Acquisition [Line Items]
Cash	(39,200)
Business Combination Provisional Information Initial Accounting Incomplete Adjustment	(500)
Business Combination Provisional Information Initial Accounting Incomplete Adjustmen	1,300
Other Current Assets	(1,400)
Property, Plant, and Equipment	2,200
Right of Use Asset	6,900
Goodwill	328,215			$ 0
Other Assets	(3,000)
Acquisition Consideration Payable	39,200
Other Current Liabilities	(1,500)
Net deferred Taxes Liability	4,500
Operating lease liabilities	(4,000)
Other Liabilities	(300)
Measurement Period Adjustments
Intangible assets	(18,900)
Goodwill	14,400
Total identifiable net assets of Altek	$ 300