Commitments and Contingent Liabilities (Narrative) (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2014	Sep. 30, 2018 USD ($) tie	Dec. 31, 2014 USD ($) tie	Dec. 31, 2013 tie	Dec. 31, 2012 USD ($)	Dec. 31, 2017 USD ($)
Product Liability Contingency
Accrued warranty		$ 9,363				$ 8,682
Number of concrete ties manufactured | tie		3,000,000
Accrual for environmental loss		$ 6,137				6,144
Reserve for concrete ties
Product Liability Contingency
Accrued warranty		$ 7,701				$ 7,595
Warranty period					5 years
2005 Contract
Product Liability Contingency
Number of concrete ties manufactured ratio | tie		1.5
Warranty policy
Product Liability Contingency
Warranty period					15 years
Warranty Ratio					1
Uprr
Product Liability Contingency
Number of concrete ties manufactured | tie		1,600,000
Warranty period					5 years
Warranty Ratio					1.5
Uprr | Reserve for concrete ties
Product Liability Contingency
Product warranty expense					$ 22,000
Litigation settlement amount					$ 12,000
Cure period to claim	90 days			90 days
Change in standard product warranty accrual			$ 8,766
Number of Concrete Ties Excluded from Warranty | tie			90,100
Uprr | Warranty policy
Product Liability Contingency
Ties manufactured that did not meet criteria to be covered as warranty replacement ties | tie				170,000
Rail Products and Services
Product Liability Contingency
Product warranty expense		$ 611