Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	$ 137,563	$ 310,803	$ 351,910
Other comprehensive income (loss) before reclassifications	43,143	(141,106)
Realized (gains) losses reclassified from accumulated other comprehensive loss in connection with loss on dilution of equity method investment		28,743
Amounts reclassified from accumulated other comprehensive loss, net of tax	20,041	16,905
Other comprehensive income (loss) from equity method investee		1,844
Total other comprehensive income (loss)	63,184	(93,614)	13,928
Less: Other comprehensive loss attributable to noncontrolling interests	(3,044)	2,580
Other comprehensive income (loss) attributable to Harsco Corporation	60,140	(91,034)
Balances	215,165	137,563	310,803
Cumulative Foreign Exchange Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(144,534)	(125,561)
Other comprehensive income (loss) before reclassifications	36,011	(53,301)
Realized (gains) losses reclassified from accumulated other comprehensive loss in connection with loss on dilution of equity method investment		28,641
Amounts reclassified from accumulated other comprehensive loss, net of tax	0	1,157
Other comprehensive income (loss) from equity method investee		1,943
Total other comprehensive income (loss)	36,011	(21,560)
Less: Other comprehensive loss attributable to noncontrolling interests	(3,044)	2,587
Other comprehensive income (loss) attributable to Harsco Corporation	32,967	(18,973)
Balances	(111,567)	(144,534)	(125,561)
Effective Portion of Derivatives Designated as Hedging Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(1,089)	(400)
Other comprehensive income (loss) before reclassifications	1,967	(1,650)
Realized (gains) losses reclassified from accumulated other comprehensive loss in connection with loss on dilution of equity method investment		1,636
Amounts reclassified from accumulated other comprehensive loss, net of tax	(70)	(263)
Other comprehensive income (loss) from equity method investee		(405)
Total other comprehensive income (loss)	1,897	(682)
Less: Other comprehensive loss attributable to noncontrolling interests	0	(7)
Other comprehensive income (loss) attributable to Harsco Corporation	1,897	(689)
Balances	808	(1,089)	(400)
Cumulative Unrecognized Actuarial Losses on Pension Obligations
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(461,094)	(389,696)
Other comprehensive income (loss) before reclassifications	5,143	(86,181)
Realized (gains) losses reclassified from accumulated other comprehensive loss in connection with loss on dilution of equity method investment		(1,534)
Amounts reclassified from accumulated other comprehensive loss, net of tax	20,111	16,011
Other comprehensive income (loss) from equity method investee		306
Total other comprehensive income (loss)	25,254	(71,398)
Less: Other comprehensive loss attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	25,254	(71,398)
Balances	(435,840)	(461,094)	(389,696)
Unrealized Loss on Marketable Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(5)	(31)
Other comprehensive income (loss) before reclassifications	22	26
Realized (gains) losses reclassified from accumulated other comprehensive loss in connection with loss on dilution of equity method investment		0
Amounts reclassified from accumulated other comprehensive loss, net of tax	0	0
Other comprehensive income (loss) from equity method investee		0
Total other comprehensive income (loss)	22	26
Less: Other comprehensive loss attributable to noncontrolling interests	0	0
Other comprehensive income (loss) attributable to Harsco Corporation	22	26
Balances	17	(5)	(31)
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances	(606,722)	(515,688)	(532,256)
Total other comprehensive income (loss)	60,140	(91,034)	16,568
Balances	$ (546,582)	$ (606,722)	$ (515,688)