Review of Operations by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Operations by segment
Revenues	$ 544,301	$ 509,398	$ 1,642,976	$ 1,355,520
Operating income from continuing operations	29,920	5,064	90,963	9,813	$ 9,813
Interest income	618	604	1,841	1,613
Interest expense	(16,004)	(15,794)	(48,854)	(43,396)
Unused debt commitment fees, amendment fees and loss on extinguishment of debt	(198)	0	(5,506)	(1,920)
Defined benefit pension income (expense)	(3,906)	(1,859)	(11,833)	(5,171)
Income (loss) from continuing operations before income taxes and equity income	18,242	(8,267)	50,277	(28,719)
Capital Expenditures	40,861	27,883	109,507	78,990
Depreciation	33,479		98,383	93,864
Depreciation Excluding Industrial Segment		32,353		93,656
Amortization	8,771	9,049	26,554	24,721
Operating Segments
Operations by segment
Operating income from continuing operations	39,480	25,278	119,778	68,507
Corporate
Operations by segment
Operating income from continuing operations	(9,560)	(20,214)	(28,815)	(58,694)
Capital Expenditures	407	62	586	444
Depreciation	491	497	1,468	1,531
Amortization	657	776	2,041	2,179
Harsco Environmental Segment | Operating Segments
Operations by segment
Revenues	269,901	222,507	800,433	668,057
Operating income from continuing operations	27,630	12,317	83,788	36,400
Capital Expenditures	34,218	21,700	94,630	65,102
Depreciation	27,179	25,588	78,446	75,626
Amortization	1,997	1,970	6,080	5,827
Harsco Clean Earth Segment | Operating Segments
Operations by segment
Revenues	200,484	194,098	585,891	434,489
Operating income from continuing operations	9,893	8,902	20,457	12,945
Capital Expenditures	5,707	2,647	12,962	7,134
Depreciation	4,576	5,010	14,818	12,769
Amortization	6,033	6,218	18,179	16,463
Harsco Rail Segment | Operating Segments
Operations by segment
Revenues	73,916	92,793	256,652	252,974
Operating income from continuing operations	1,957	4,059	15,533	19,162
Capital Expenditures	529	3,474	1,329	6,310
Depreciation	1,233	1,258	3,651	3,730
Amortization	$ 84	$ 85	$ 254	$ 252