Reconciliation of Basic and Diluted Shares - Reconciliation of Basic and Diluted Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Income (loss) from continuing operations, net of tax	$ (2,852)	$ 31,110	$ 7,622	$ 41,613
Weighted-average shares outstanding - basic (in shares)	80,328	80,861	80,119	80,756
Dilutive effect of stock-based compensation (in shares)	0	2,782	1,955	2,838
Weighted-average shares outstanding - diluted (in shares)	80,328	83,643	82,074	83,594
Earnings (loss) from continuing operations per common share, attributable to Harsco Corporation common stockholders:
Basic (in dollars per share)	$ (0.04)	$ 0.38	$ 0.10	$ 0.52
Diluted (in dollars per share)	$ (0.04)	$ 0.37	$ 0.09	$ 0.50