CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 1,565	$ 1,227
Other comprehensive income (loss):
Foreign currency translation adjustments, net of deferred income taxes	(3,296)	(58,566)
Net loss on cash flow hedging instruments, net of deferred income taxes	689	(1,687)
Pension liability adjustments, net of deferred income taxes	3,819	30,269
Unrealized gain (loss) on marketable securities, net of deferred income taxes	17	(18)
Total other comprehensive income (loss)	1,229	(30,002)
Total comprehensive income (loss)	2,794	(28,775)
Less: Comprehensive (income) loss attributable to noncontrolling interests	(364)	61
Comprehensive income (loss) attributable to Harsco Corporation	$ 2,430	$ (28,714)