Components of Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2019	Jan. 01, 2018
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	$ 349,114	$ 335,272	$ 313,376	$ 266,153	$ 246,345	$ 215,165	$ 313,376	$ 215,165
Accumulated other comprehensive loss				1	(13)			1	$ 0	$ 2,387
Other comprehensive income (loss) before reclassifications							(14,753)	(24,151)
Amounts reclassified from accumulated other comprehensive loss							13,662	14,350
Total other comprehensive income (loss)	(9,220)	3,598	4,531	1,226	(17,190)	6,163	(1,091)	(9,801)
Other comprehensive income attributable to noncontrolling interests							1,868	2,612
Other comprehensive income (loss) attributable to Harsco Corporation							777	(7,189)
Balances	751,260	349,114	335,272	304,391	266,153	246,345	751,260	304,391
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances			(159,810)			(111,567)	(159,810)	(111,567)
Accumulated other comprehensive loss									0
Other comprehensive income (loss) before reclassifications							(20,513)	(40,157)
Amounts reclassified from accumulated other comprehensive loss							(1,763)	0
Total other comprehensive income (loss)							(22,276)	(40,157)
Other comprehensive income attributable to noncontrolling interests							1,868	2,612
Other comprehensive income (loss) attributable to Harsco Corporation							(20,408)	(37,545)
Balances	(180,218)			(149,112)			(180,218)	(149,112)
Effective Portion of Deriviatives Designated as Hedging Instruments
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances			1,389			808	1,389	808
Accumulated other comprehensive loss									0
Other comprehensive income (loss) before reclassifications							(5,889)	6,055
Amounts reclassified from accumulated other comprehensive loss							1,404	26
Total other comprehensive income (loss)							(4,485)	6,081
Other comprehensive income attributable to noncontrolling interests							0	0
Other comprehensive income (loss) attributable to Harsco Corporation							(4,485)	6,081
Balances	(3,096)			5,369			(3,096)	5,369
Cumulative Unrecognized Actuarial Losses on Pension Obligations
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances			(408,655)			(435,840)	(408,655)	(435,840)
Accumulated other comprehensive loss									(21,429)
Other comprehensive income (loss) before reclassifications							11,630	9,970
Amounts reclassified from accumulated other comprehensive loss							14,021	14,324
Total other comprehensive income (loss)							25,651	24,294
Other comprehensive income attributable to noncontrolling interests							0	0
Other comprehensive income (loss) attributable to Harsco Corporation							25,651	24,294
Balances	(404,433)			(411,546)			(404,433)	(411,546)
Unrealized Loss on Marketable Securities
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances			(31)			17	(31)	17
Accumulated other comprehensive loss									0
Other comprehensive income (loss) before reclassifications							19	(19)
Amounts reclassified from accumulated other comprehensive loss							0	0
Total other comprehensive income (loss)							19	(19)
Other comprehensive income attributable to noncontrolling interests							0	0
Other comprehensive income (loss) attributable to Harsco Corporation							19	(19)
Balances	(12)			(2)			(12)	(2)
Accumulated Other Comprehensive Loss
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	(580,229)	(584,425)	(567,107)	(557,889)	(543,217)	(546,582)	(567,107)	(546,582)
Accumulated other comprehensive loss									$ (21,429)	(1,520)
Total other comprehensive income (loss)	(7,530)	4,196	4,111	2,598	(14,672)	4,885
Balances	$ (587,759)	$ (580,229)	$ (584,425)	$ (555,291)	$ (557,889)	(543,217)	$ (587,759)	$ (555,291)
Accounting Standards Update 2014-09 | Accumulated Other Comprehensive Loss
Components of Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss						$ (1,520)
Accounting Standards Update 2014-09 | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Components of Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss										$ (1,520)