Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Jan. 01, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	$ 313,376	$ 215,165	$ 137,563
Adoption of new accounting standard				$ 0	$ 2,374
Other comprehensive income (loss) before reclassifications	(22,035)	(39,875)
Amounts reclassified from accumulated other comprehensive loss, net of tax	21,977	18,370
Total other comprehensive income (loss)	(58)	(21,505)	63,184
Less: Other comprehensive loss attributable to noncontrolling interests	972	2,500
Other comprehensive income (loss) attributable to Harsco Corporation	914	(19,005)
Balances	789,659	313,376	215,165
Cumulative Foreign Exchange Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(159,810)	(111,567)
Adoption of new accounting standard				0	0
Other comprehensive income (loss) before reclassifications	17,261	(50,743)
Amounts reclassified from accumulated other comprehensive loss, net of tax	(1,763)	0
Total other comprehensive income (loss)	15,498	(50,743)
Less: Other comprehensive loss attributable to noncontrolling interests	972	2,500
Other comprehensive income (loss) attributable to Harsco Corporation	16,470	(48,243)
Balances	(143,340)	(159,810)	(111,567)
Effective Portion of Derivatives Designated as Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	1,389	808
Adoption of new accounting standard				0	(1,520)
Other comprehensive income (loss) before reclassifications	(7,050)	2,466
Amounts reclassified from accumulated other comprehensive loss, net of tax	1,944	(365)
Total other comprehensive income (loss)	(5,106)	2,101
Less: Other comprehensive loss attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	(5,106)	2,101
Balances	(3,717)	1,389	808
Cumulative Unrecognized Actuarial Losses on Pension Obligations
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(408,655)	(435,840)
Adoption of new accounting standard				(21,429)	0
Other comprehensive income (loss) before reclassifications	(32,274)	8,450
Amounts reclassified from accumulated other comprehensive loss, net of tax	21,796	18,735
Total other comprehensive income (loss)	(10,478)	27,185
Less: Other comprehensive loss attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	(10,478)	27,185
Balances	(440,562)	(408,655)	(435,840)
Unrealized Loss on Marketable Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(31)	17
Adoption of new accounting standard				0	0
Other comprehensive income (loss) before reclassifications	28	(48)
Amounts reclassified from accumulated other comprehensive loss, net of tax	0	0
Total other comprehensive income (loss)	28	(48)
Less: Other comprehensive loss attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	28	(48)
Balances	(3)	(31)	17
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(567,107)	(546,582)	(606,722)
Adoption of new accounting standard				$ (21,429)	$ (1,520)
Total other comprehensive income (loss)	914	(19,005)	60,140
Balances	(587,622)	(567,107)	(546,582)
Accounting Standards Update 2014-09
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(588,536)	(548,102)
Balances		(588,536)	(548,102)
Accounting Standards Update 2014-09 | Cumulative Foreign Exchange Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(159,810)	(111,567)
Balances		(159,810)	(111,567)
Accounting Standards Update 2014-09 | Effective Portion of Derivatives Designated as Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	1,389	(712)
Balances		1,389	(712)
Accounting Standards Update 2014-09 | Cumulative Unrecognized Actuarial Losses on Pension Obligations
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(430,084)	(435,840)
Balances		(430,084)	(435,840)
Accounting Standards Update 2014-09 | Unrealized Loss on Marketable Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	$ (31)	17
Balances		$ (31)	$ 17