Components of Accumulated Other Comprehensive Loss - Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 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]
Balances	$ 789,659	$ 313,376
Other comprehensive income (loss) before reclassifications	(51,103)	2,083
Amounts reclassified from accumulated other comprehensive loss	21,101	2,448
Total other comprehensive income (loss)	(30,002)	4,531
Other comprehensive income attributable to noncontrolling interests	1,148	(420)
Other comprehensive income (loss) attributable to Harsco Corporation	(28,854)	4,111
Balances	758,870	335,272
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	(143,340)	(159,810)
Other comprehensive income (loss) before reclassifications	(71,472)	11,725
Amounts reclassified from accumulated other comprehensive loss	12,906	(2,271)
Total other comprehensive income (loss)	(58,566)	9,454
Other comprehensive income attributable to noncontrolling interests	1,148	(420)
Other comprehensive income (loss) attributable to Harsco Corporation	(57,418)	9,034
Balances	(200,758)	(150,776)
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]
Balances	(3,717)	1,389
Other comprehensive income (loss) before reclassifications	(1,042)	(3,084)
Amounts reclassified from accumulated other comprehensive loss	(645)	(63)
Total other comprehensive income (loss)	(1,687)	(3,147)
Other comprehensive income attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	(1,687)	(3,147)
Balances	(5,404)	(1,758)
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]
Balances	(440,562)	(408,655)
Other comprehensive income (loss) before reclassifications	21,429	(6,573)
Amounts reclassified from accumulated other comprehensive loss	8,840	4,782
Total other comprehensive income (loss)	30,269	(1,791)
Other comprehensive income attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	30,269	(1,791)
Balances	(410,293)	(431,875)
Unrealized Loss on Marketable Securities
Components of Accumulated Other Comprehensive Income [Roll Forward]
Balances	(3)	(31)
Other comprehensive income (loss) before reclassifications	(18)	15
Amounts reclassified from accumulated other comprehensive loss	0	0
Total other comprehensive income (loss)	(18)	15
Other comprehensive income attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	(18)	15
Balances	(21)	(16)
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]
Balances	(587,622)	(567,107)
Total other comprehensive income (loss)	(28,854)	4,111
Balances	$ (616,476)	$ (584,425)