Commitments and Contingent Liabilites (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) item	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 item	Dec. 31, 2012 USD ($)	Dec. 31, 2016 USD ($)
Product Liability Contingency [Line Items]
Concrete Ties Manufactured | item	3,000,000
Standard Product Warranty Accrual	$ 10,204				$ 10,154
Warranty period				10 years
Accrual for Environmental Loss Contingencies	6,251				6,270
Reserve for Concrete Ties [Member]
Product Liability Contingency [Line Items]
Standard Product Warranty Accrual	$ 7,578				$ 7,574
Warranty period				5 years
2005 Contract [Member]
Product Liability Contingency [Line Items]
Concrete Ties Manufactured | item	1,500,000
Period in which concrete ties will be replaced after sale	5 years
Warranty Policy [Member]
Product Liability Contingency [Line Items]
Warranty period				15 years
Warranty Ratio				1.00
The UPRR [Member]
Product Liability Contingency [Line Items]
Concrete Ties Manufactured | item	1,600,000
Warranty period				5 years
Warranty Ratio				1.50
The UPRR [Member] | Reserve for Concrete Ties [Member]
Product Liability Contingency [Line Items]
Litigation Settlement, Amount				$ 12,000
Unreconciled warranty ties | item		90,100
Product Warranty Expense				$ 22,000
Cure period to claim		90 days
Standard Product Warranty Accrual, Period Increase (Decrease)		$ 8,766
The UPRR [Member] | Warranty Policy [Member]
Product Liability Contingency [Line Items]
Ties manufactured that did not meet criteria to be covered as warranty replacement ties | item			170,000