Reconciliation of Basic and Diluted Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Income from continuing operations, net of tax	$ 18,260	$ 9,267
Weighted-average shares outstanding - basic (in shares)	80,650	80,385
Dilutive effect of stock-based compensation (in shares)	2,894	1,878
Weighted-average shares outstanding - diluted (in shares)	83,544	82,263
Earnings (loss) from continuing operations per common share, attributable to Harsco Corporation common stockholders:
Basic (in dollars per share)	$ 0.23	$ 0.12
Diluted (in dollars per share)	$ 0.22	$ 0.11