Components of Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Jan. 01, 2018
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	$ 335,272	$ 313,376	$ 246,345	$ 215,165	$ 313,376	$ 215,165
Accumulated other comprehensive loss			(13)			(13)	$ 0	$ 2,387
Other comprehensive income (loss) before reclassifications					(901)	(20,735)
Amounts reclassified from accumulated other comprehensive loss					9,030	9,708
Total other comprehensive income (loss)	3,598	4,531	(17,190)	6,163	8,129	(11,027)
Other comprehensive income attributable to noncontrolling interests					178	1,240
Other comprehensive income (loss) attributable to Harsco Corporation					8,307	(9,787)
Balances	349,114	335,272	266,153	246,345	349,114	266,153
Cumulative Foreign Exchange Translation Adjustments
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					2,775	(36,205)
Amounts reclassified from accumulated other comprehensive loss					(2,271)	0
Total other comprehensive income (loss)					504	(36,205)
Other comprehensive income attributable to noncontrolling interests					178	1,240
Other comprehensive income (loss) attributable to Harsco Corporation					682	(34,965)
Balances	(159,128)		(146,532)		(159,128)	(146,532)
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					(5,893)	5,482
Amounts reclassified from accumulated other comprehensive loss					1,722	97
Total other comprehensive income (loss)					(4,171)	5,579
Other comprehensive income attributable to noncontrolling interests					0	0
Other comprehensive income (loss) attributable to Harsco Corporation					(4,171)	5,579
Balances	(2,782)		4,867		(2,782)	4,867
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					2,192	10,015
Amounts reclassified from accumulated other comprehensive loss					9,579	9,611
Total other comprehensive income (loss)					11,771	19,626
Other comprehensive income attributable to noncontrolling interests					0	0
Other comprehensive income (loss) attributable to Harsco Corporation					11,771	19,626
Balances	(418,313)		(416,214)		(418,313)	(416,214)
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					25	(27)
Amounts reclassified from accumulated other comprehensive loss					0	0
Total other comprehensive income (loss)					25	(27)
Other comprehensive income attributable to noncontrolling interests					0	0
Other comprehensive income (loss) attributable to Harsco Corporation					25	(27)
Balances	(6)		(10)		(6)	(10)
Accumulated Other Comprehensive Loss
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	(584,425)	(567,107)	(543,217)	(546,582)	(567,107)	(546,582)
Accumulated other comprehensive loss							$ (21,429)	(1,520)
Total other comprehensive income (loss)	4,196	4,111	(14,672)	4,885
Balances	$ (580,229)	$ (584,425)	$ (557,889)	(543,217)	$ (580,229)	$ (557,889)
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)