Employee Benefit Plans (Details 3) - Pension Plan $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) market	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Expected long-term rates of return on plan assets for next year (as a percent)	5.60%
Expected long-term rates of return on plan assets	5.90%	6.00%	6.20%
International, Other Than United Kingdom [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Pension plan assets as a percentage of international plan assets				5.00%
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation				$ 294,700	$ 286,000
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation				294,700	279,200
Accumulated benefit obligation				294,700	279,200
Fair value of plan assets				$ 226,300	$ 196,600
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Number of capital market results simulated in the model for expected return on plan assets | market	1,000
Period for which results of capital markets are simulated	20 years
Expected long-term rates of return on plan assets for next year (as a percent)	7.00%
Expected long-term rates of return on plan assets	7.30%	7.30%	7.30%
Number of shares of Company's common stock included in plan assets | shares				360,000	450,000
Value of shares of Company's common stock included in plan assets				$ 8,300	$ 8,900
Fair values of plan assets	$ 205,388	$ 205,388	$ 229,941	$ 226,268	$ 205,388
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	205,388	229,941
Employer contributions	8,306	10,294
Fair value of plan assets at end of year	226,268	205,388	$ 229,941
U.S. Plans | Domestic equity securities
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				30.80%	30.60%
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	8,937	8,937		$ 8,285	$ 8,937
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	8,937
Fair value of plan assets at end of year	8,285	8,937
U.S. Plans | Domestic equity securities | Minimum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				27.00%
U.S. Plans | Domestic equity securities | Maximum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				37.00%
U.S. Plans | Domestic mutual funds—equities
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	54,002	54,002		$ 61,346	$ 54,002
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	54,002
Fair value of plan assets at end of year	61,346	54,002
U.S. Plans | International equity securities
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				25.30%	22.00%
U.S. Plans | International equity securities | Minimum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				20.00%
U.S. Plans | International equity securities | Maximum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				30.00%
U.S. Plans | International equities—mutual funds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	45,195	45,195		$ 57,188	$ 45,195
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	45,195
Fair value of plan assets at end of year	57,188	45,195
U.S. Plans | Harsco common stock
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				3.70%	4.40%
U.S. Plans | Fixed income securities
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				34.80%	42.90%
U.S. Plans | Fixed income securities | Minimum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				35.00%
U.S. Plans | Fixed income securities | Maximum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				45.00%
U.S. Plans | Mutual funds - bonds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	88,107	88,107		$ 78,685	$ 88,107
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	88,107
Fair value of plan assets at end of year	78,685	88,107
U.S. Plans | Other
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				8.30%	3.80%
U.S. Plans | Other | Minimum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				0.00%
U.S. Plans | Other | Maximum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				10.00%
U.S. Plans | Other mutual funds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	7,703	7,703		$ 8,764	$ 7,703
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	7,703
Fair value of plan assets at end of year	8,764	7,703
U.S. Plans | Cash and cash equivalents
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				0.80%	0.70%
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	1,444	1,444		$ 1,816	$ 1,444
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	1,444
Fair value of plan assets at end of year	1,816	1,444
U.S. Plans | Cash and cash equivalents | Maximum
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				0.00%
U.S. Plans | Partnership [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	10,184			$ 10,184
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	10,184
U.S. Plans | Level 1
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	205,388	205,388		216,084	205,388
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	205,388
Fair value of plan assets at end of year	216,084	205,388
U.S. Plans | Level 1 | Domestic equity securities
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	8,937	8,937		8,285	8,937
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	8,937
Fair value of plan assets at end of year	8,285	8,937
U.S. Plans | Level 1 | Domestic mutual funds—equities
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	54,002	54,002		61,346	54,002
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	54,002
Fair value of plan assets at end of year	61,346	54,002
U.S. Plans | Level 1 | International equities—mutual funds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	45,195	45,195		57,188	45,195
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	45,195
Fair value of plan assets at end of year	57,188	45,195
U.S. Plans | Level 1 | Mutual funds - bonds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	88,107	88,107		78,685	88,107
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	88,107
Fair value of plan assets at end of year	78,685	88,107
U.S. Plans | Level 1 | Other mutual funds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	7,703	7,703		8,764	7,703
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	7,703
Fair value of plan assets at end of year	8,764	7,703
U.S. Plans | Level 1 | Cash and cash equivalents
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	1,444	1,444		1,816	1,444
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	1,444
Fair value of plan assets at end of year	1,816	$ 1,444
U.S. Plans | Level 1 | Partnership [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	0			0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	0
U.S. Plans | Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	10,184			10,184
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	10,184
U.S. Plans | Fair Value Measured at Net Asset Value Per Share [Member] | Partnership [Member]
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	10,184			10,184
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at end of year	$ 10,184
International Plans
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation				982,700	869,400
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation				966,300	831,700
Accumulated benefit obligation				961,100	828,900
Fair value of plan assets				841,900	701,400
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Expected long-term rates of return on plan assets for next year (as a percent)	5.20%
Expected long-term rates of return on plan assets	5.50%	5.60%	5.90%
Fair values of plan assets	$ 864,636	$ 842,717	$ 842,717	$ 864,636	$ 744,538
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	744,538	842,717
Employer contributions	21,121	18,415
Fair value of plan assets at end of year	864,636	744,538	$ 842,717
International Plans | Equity Securities [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				31.60%	29.20%
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				29.00%
International Plans | Mutual funds - equities
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	217,321	217,321		$ 273,568	$ 217,321
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	217,321
Fair value of plan assets at end of year	273,568	217,321
International Plans | Fixed income securities
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				48.50%	50.70%
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				50.00%
International Plans | Mutual funds - bonds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	372,094	372,094		$ 413,249	$ 372,094
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	372,094
Fair value of plan assets at end of year	413,249	372,094
International Plans | Insurance contracts
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	5,620	5,620		$ 5,705	$ 5,620
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	5,620
Fair value of plan assets at end of year	5,705	5,620
International Plans | Other
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				19.60%	19.80%
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				21.00%
International Plans | Other mutual funds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	147,313	147,313		$ 169,886	$ 147,313
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	147,313
Fair value of plan assets at end of year	169,886	147,313
International Plans | Cash and cash equivalents
Defined Benefit Plan, Information about Plan Assets [Abstract]
Percentage of Plan Assets at December 31				0.30%	0.30%
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Target Long-Term Allocation (less than 5% for Cash and cash equivalents)				0.00%
Fair values of plan assets	2,190	2,190		$ 2,228	$ 2,190
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	2,190
Fair value of plan assets at end of year	2,228	2,190
International Plans | Level 1
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	2,190	2,190		2,228	2,190
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	2,190
Fair value of plan assets at end of year	2,228	2,190
International Plans | Level 1 | Mutual funds - equities
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
International Plans | Level 1 | Mutual funds - bonds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
International Plans | Level 1 | Insurance contracts
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets				0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year
Fair value of plan assets at end of year	0
International Plans | Level 1 | Other mutual funds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	0	0		0	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	0	0
International Plans | Level 1 | Cash and cash equivalents
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	2,190	2,190		2,228	2,190
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	2,190
Fair value of plan assets at end of year	2,228	2,190
International Plans | Level 2
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	742,348	742,348		862,408	742,348
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	742,348
Fair value of plan assets at end of year	862,408	742,348
International Plans | Level 2 | Mutual funds - equities
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	217,321	217,321		273,568	217,321
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	217,321
Fair value of plan assets at end of year	273,568	217,321
International Plans | Level 2 | Mutual funds - bonds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	372,094	372,094		413,249	372,094
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	372,094
Fair value of plan assets at end of year	413,249	372,094
International Plans | Level 2 | Insurance contracts
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	5,620	5,620		5,705	5,620
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	5,620
Fair value of plan assets at end of year	5,705	5,620
International Plans | Level 2 | Other mutual funds
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	147,313	147,313		169,886	147,313
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	147,313
Fair value of plan assets at end of year	169,886	147,313
International Plans | Level 2 | Cash and cash equivalents
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Fair values of plan assets	0	0		$ 0	$ 0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0
Fair value of plan assets at end of year	$ 0	$ 0
United Kingdom
Defined Benefit Plan, Plan Assets, Allocations [Abstract]
Expected long-term rates of return on plan assets for next year (as a percent)	5.20%	5.50%
Pension plan assets as a percentage of international plan assets				95.00%