Capital Stock - Reconciliation of the average shares of common stock used to compute basic earnings per common share to the shares used to compute diluted earnings per common share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of the average shares of common stock used to compute basic earnings per common share to the shares used to compute diluted earnings per common share
Income (loss) from continuing operations attributable to Harsco Corporation common stockholders (in dollars)	$ (45,519)	$ (137,155)	$ 22,137
Weighted average shares of common stock outstanding	79,796	79,493	79,234
Dilutive effect of stock-based compensation (in shares)	0	0	1,055
Weighted-average shares outstanding—diluted (in shares)	79,796	79,493	80,289
Basic (in dollars per share)	$ (0.57)	$ (1.73)	$ 0.28
Diluted (in dollars per share)	$ (0.57)	$ (1.73)	$ 0.28