Components of Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019	Jan. 01, 2018
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	$ 313,376	$ 215,165
Accumulated other comprehensive loss		0		$ (2,387)
Other comprehensive income (loss) before reclassifications	2,083	1,310
Amounts reclassified from accumulated other comprehensive loss	2,448	4,853
Total other comprehensive income	4,531	6,163
Other comprehensive income attributable to noncontrolling interests	(420)	(1,278)
Other comprehensive income (loss) attributable to Harsco Corporation	4,111	4,885
Balances	335,272	246,345
Cumulative Foreign Exchange Translation Adjustments
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	(159,810)	(111,567)
Accumulated other comprehensive loss			$ 0
Other comprehensive income (loss) before reclassifications	11,725	12,501
Amounts reclassified from accumulated other comprehensive loss	(2,271)	0
Total other comprehensive income	9,454	12,501
Other comprehensive income attributable to noncontrolling interests	(420)	(1,278)
Other comprehensive income (loss) attributable to Harsco Corporation	9,034	11,223
Balances	(150,776)	(100,344)
Effective Portion of Deriviatives Designated as Hedging Instruments
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	1,389	808
Accumulated other comprehensive loss			0
Other comprehensive income (loss) before reclassifications	(3,084)	2,768
Amounts reclassified from accumulated other comprehensive loss	(63)	(91)
Total other comprehensive income	(3,147)	2,677
Other comprehensive income attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	(3,147)	2,677
Balances	(1,758)	1,965
Cumulative Unrecognized Actuarial Losses on Pension Obligations
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	(408,655)	(435,840)
Accumulated other comprehensive loss			(21,429)
Other comprehensive income (loss) before reclassifications	(6,573)	(13,945)
Amounts reclassified from accumulated other comprehensive loss	4,782	4,944
Total other comprehensive income	(1,791)	(9,001)
Other comprehensive income attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	(1,791)	(9,001)
Balances	(431,875)	(444,841)
Unrealized Loss on Marketable Securities
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	(31)	17
Accumulated other comprehensive loss			0
Other comprehensive income (loss) before reclassifications	15	(14)
Amounts reclassified from accumulated other comprehensive loss	0	0
Total other comprehensive income	15	(14)
Other comprehensive income attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	15	(14)
Balances	(16)	3
Accumulated Other Comprehensive Loss
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	(567,107)	(546,582)
Accumulated other comprehensive loss		21,429	$ (21,429)	(1,520)
Total other comprehensive income	4,111	4,885
Balances	$ (584,425)	(543,217)
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)