CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 1,227	$ 22,537
Other comprehensive income (loss):
Foreign currency translation adjustments, net of deferred income taxes of $(4,082) and $1,131 for the three months ended March 31, 2020 and 2019, respectively	(58,566)	9,454
Net gain (loss) on cash flow hedging instruments, net of deferred income taxes of $517 and $945 for the three months ended March 31, 2020 and 2019, respectively	(1,687)	(3,147)
Pension liability adjustments, net of deferred income taxes of $(1,710) and $(342) for the three months ended March 31, 2020 and 2019, respectively	30,269	(1,791)
Unrealized gain (loss) on marketable securities, net of deferred income taxes of $8 and $(5) for the three months ended March 31, 2020 and 2019, respectively	(18)	15
Total other comprehensive income (loss)	(30,002)	4,531
Total comprehensive income (loss)	(28,775)	27,068
Less: Comprehensive (income) loss attributable to noncontrolling interests	61	(2,260)
Comprehensive income (loss) attributable to Harsco Corporation	$ (28,714)	$ 24,808