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U.K. Operations Optimization Restructuring Reserve Roll Forward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and related costs	$ 9,362	$ 2,361	$ 9,645	$ 6,116
U.K. Operations Optimization [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and related liability, beginning balance			0
Restructuring and related costs	9,355		9,355
Cash payments			(1,992)
Non-cash settlements			(1,120)
Restructuring and related liability, ending balance	6,243		6,243
U.K. Operations Optimization [Member] \| Rationalization of locomotive and railcar fleet [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and related liability, beginning balance			0
Restructuring and related costs	5,938		5,938
Cash payments			(307)
Non-cash settlements			(897)
Restructuring and related liability, ending balance	4,734		4,734
U.K. Operations Optimization [Member] \| Management restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and related liability, beginning balance			0
Restructuring and related costs	2,129		2,129
Cash payments			(620)
Non-cash settlements			0
Restructuring and related liability, ending balance	1,509		1,509
U.K. Operations Optimization [Member] \| Productivity and automation investments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and related liability, beginning balance			0
Restructuring and related costs	1,288		1,288
Cash payments			(1,065)
Non-cash settlements			(223)
Restructuring and related liability, ending balance	$ 0		$ 0