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
	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Income (loss) from continuing operations, net of tax	$ (7,333)	$ (1,565)
Weighted-average shares outstanding - basic (in shares)	79,363	79,088
Dilutive effect of stock-based compensation (in shares)	0	0
Weighted-average shares outstanding - diluted (in shares)	79,363	79,088
Earnings (loss) from continuing operations per common share, attributable to Harsco Corporation common stockholders:
Basic (in dollars per share)	$ (0.09)	$ (0.02)
Diluted (in dollars per share)	$ (0.09)	$ (0.02)