Capital Stock (Details 2) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Stock
Shares outstanding at the beginning of the period	113,473,951	112,888,126	112,499,874	112,405,302
Treasury stock, shares	33,928,928	32,434,274	32,324,911	32,310,937
Common Stock, Shares, Outstanding	79,545,023	80,453,852	80,174,963	80,094,365
Vested Restricted Stock Units (in shares)	545,908	375,355	94,572
Stock issued during period, stock appreciation rights (in shares)	39,917	12,897
Treasury shares purchased	0
Shares outstanding at the end of the period	113,473,951	112,888,126	112,499,874
Treasury Stock, Shares	33,928,928	32,434,274	32,324,911
Common Stock, Shares, Outstanding	79,545,023	80,453,852	80,174,963
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)	$ 136,783	$ 7,626	$ (86,336)
Weighted average shares of common stock outstanding	80,716,000	80,553,000	80,333,000
Dilutive effect of stock-based compensation (in shares)	2,879,000	2,287,000	0
Weighted-average shares outstanding—diluted (in shares)	83,595,000	82,840,000	80,333,000
Earnings (loss) from continuing operations per common share, attributable to Harsco Corporation common stockholders:
Basic (in dollars per share)	$ 1.69	$ 0.09	$ (1.07)
Income (Loss) from Continuing Operations, Per Diluted Share	$ 1.64	$ 0.09	$ (1.07)
Treasury Stock
Common Stock
Vested Restricted Stock Units (in shares)	161,774	105,431	13,974
Stock issued during period, stock appreciation rights (in shares)	11,808	3,932
Treasury shares purchased	(1,321,072)	0	0
Outstanding Shares
Common Stock
Vested Restricted Stock Units (in shares)	384,134	269,924	80,598
Stock issued during period, stock appreciation rights (in shares)	28,109	8,965
Treasury shares purchased	(1,321,072)