Components of Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jan. 01, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets							$ 0
Components of Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 758,870	$ 789,659	$ 335,272	$ 313,376	$ 789,659	$ 313,376
Other comprehensive income (loss) before reclassifications					(43,044)	(901)
Amounts reclassified from accumulated other comprehensive loss					26,073	9,030
Total other comprehensive income	13,031	(30,002)	3,598	4,531	(16,971)	8,129
Other comprehensive income attributable to noncontrolling interests					975	178
Other comprehensive income (loss) attributable to Harsco Corporation					(15,996)	8,307
Ending balance	764,516	758,870	349,114	335,272	764,516	349,114
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Components of Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		(143,340)		(159,810)	(143,340)	(159,810)
Other comprehensive income (loss) before reclassifications					(65,677)	2,775
Amounts reclassified from accumulated other comprehensive loss					12,906	(2,271)
Total other comprehensive income					(52,771)	504
Other comprehensive income attributable to noncontrolling interests					975	178
Other comprehensive income (loss) attributable to Harsco Corporation					(51,796)	682
Ending balance	(195,136)		(159,128)		(195,136)	(159,128)
Effective Portion of Deriviatives Designated as Hedging Instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets							0
Components of Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		(3,717)		1,389	(3,717)	1,389
Other comprehensive income (loss) before reclassifications					(1,146)	(5,893)
Amounts reclassified from accumulated other comprehensive loss					(213)	1,722
Total other comprehensive income					(1,359)	(4,171)
Other comprehensive income attributable to noncontrolling interests					0	0
Other comprehensive income (loss) attributable to Harsco Corporation					(1,359)	(4,171)
Ending balance	(5,076)		(2,782)		(5,076)	(2,782)
Cumulative Unrecognized Actuarial Losses on Pension Obligations
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets							(21,429)
Components of Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		(440,562)		(408,655)	(440,562)	(408,655)
Other comprehensive income (loss) before reclassifications					23,810	2,192
Amounts reclassified from accumulated other comprehensive loss					13,380	9,579
Total other comprehensive income					37,190	11,771
Other comprehensive income attributable to noncontrolling interests					0	0
Other comprehensive income (loss) attributable to Harsco Corporation					37,190	11,771
Ending balance	(403,372)		(418,313)		(403,372)	(418,313)
Unrealized Loss on Marketable Securities
Components of Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		(3)		(31)	(3)	(31)
Other comprehensive income (loss) before reclassifications					(31)	25
Amounts reclassified from accumulated other comprehensive loss					0	0
Total other comprehensive income					(31)	25
Other comprehensive income attributable to noncontrolling interests					0	0
Other comprehensive income (loss) attributable to Harsco Corporation					(31)	25
Ending balance	(34)		(6)		(34)	(6)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets							$ (21,429)
Components of Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(616,476)	(587,622)	(584,425)	(567,107)	(587,622)	(567,107)
Total other comprehensive income	12,858	(28,854)	4,196	4,111
Ending balance	$ (603,618)	$ (616,476)	$ (580,229)	$ (584,425)	$ (603,618)	$ (580,229)