Acquisitions and Dispositions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	9 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Jun. 28, 2019	Dec. 31, 2018	Jun. 30, 2018
Business Acquisition [Line Items]
Goodwill		$ 717,727		$ 404,713
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)
Acquisition consideration payable			(39,200)
Other current liabilities			(20,500)
Net deferred taxes liabilities			(51,200)
Operating lease liabilities			(11,100)
Other liabilities			(11,900)
Total identifiable net assets of Altek			628,000
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