Capital Stock (Details 2) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock
Shares outstanding at the beginning of the period	114,720,347	113,473,951	112,888,126	112,499,874
Treasury stock, shares	36,205,589	33,928,928	32,434,274	32,324,911
Common Stock, Shares, Outstanding	78,514,758	79,545,023	80,453,852	80,174,963
Vested Restricted Stock Units (in shares)	321,965	545,908	375,355
Stock Issued During Period, Shares, Other	908,566
Stock issued during period, stock appreciation rights (in shares)	15,865	39,917	12,897
Treasury shares purchased	0	0
Shares outstanding at the end of the period	114,720,347	113,473,951	112,888,126
Treasury Stock, Shares	36,205,589	33,928,928	32,434,274
Common Stock, Shares, Outstanding	78,514,758	79,545,023	80,453,852
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)	$ 28,231	$ 100,578	$ (6,810)
Weighted average shares of common stock outstanding	79,632,000	80,716,000	80,553,000
Dilutive effect of stock-based compensation (in shares)	1,743,000	2,879,000	0
Weighted-average shares outstanding—diluted (in shares)	81,375,000	83,595,000	80,553,000
Earnings (loss) from continuing operations per common share, attributable to Harsco Corporation common stockholders:
Basic (in dollars per share)	$ 0.35	$ 1.25	$ (0.08)
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.35	$ 1.20	$ (0.08)
Treasury Stock
Common Stock
Vested Restricted Stock Units (in shares)	125,863	161,774	105,431
Stock Issued During Period, Shares, Other	379,353
Stock issued during period, stock appreciation rights (in shares)	4,619	11,808	3,932
Treasury shares purchased	1,766,826	1,321,072	0
Outstanding Shares
Common Stock
Vested Restricted Stock Units (in shares)	196,102	384,134	269,924
Stock Issued During Period, Shares, Other	529,213
Stock issued during period, stock appreciation rights (in shares)	11,246	28,109	8,965
Treasury shares purchased	1,766,826	1,321,072