Capital Stock (Details 2) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock
Shares outstanding at the beginning of the period		112,888,126	112,499,874	112,405,302	112,357,348
Treasury stock, shares	[1]	32,434,274	32,324,911	32,310,937	31,697,498
Common Stock, Shares, Outstanding		80,453,852	80,174,963	80,094,365	80,659,850
Vested Restricted Stock Units (in shares)		375,355	94,572	47,954
Stock issued during period, stock appreciation rights		12,897
Treasury shares purchased				0
Shares outstanding at the end of the period		112,888,126	112,499,874	112,405,302
Treasury Stock, Shares	[1]	32,434,274	32,324,911	32,310,937
Common Stock, Shares, Outstanding		80,453,852	80,174,963	80,094,365
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)		$ 7,626	$ (86,336)	$ 7,168
Weighted average shares of common stock outstanding		80,553,000	80,333,000	80,234,000
Dilutive effect of stock-based compensation (in shares)		2,287,000	0	131,000
Weighted-average shares outstanding—diluted (in shares)		82,840,000	80,333,000	80,365,000
Earnings (loss) from continuing operations per common share, attributable to Harsco Corporation common stockholders:
Basic (in dollars per share)		$ 0.09	$ (1.07)	$ 0.09
Income (Loss) from Continuing Operations, Per Diluted Share		$ 0.09	$ (1.07)	$ 0.09
Treasury Stock
Common Stock
Vested Restricted Stock Units (in shares)	[1]	105,431	13,974	16,807
Stock issued during period, stock appreciation rights	[1]	3,932
Treasury shares purchased		0	0	(596,632)
Outstanding Shares
Common Stock
Vested Restricted Stock Units (in shares)		269,924	80,598	31,147
Stock issued during period, stock appreciation rights		8,965
Treasury shares purchased				(596,632)

[1] The Company repurchases shares in connection with the issuance of shares under stock-based compensation programs and in accordance with Board authorized share repurchase programs.