Commitments and Contingent Liabilites (Narrative) (Details) $ in Thousands, item in Millions	12 Months Ended		168 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 item	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Product Liability Contingency [Line Items]
Concrete Ties Manufactured | item			3.0
Standard Product Warranty Accrual				$ 8,731	$ 8,755
Accrual for Environmental Loss Contingencies				6,612	6,640
Reserve for Concrete Ties [Member]
Product Liability Contingency [Line Items]
Litigation Settlement, Amount		$ 12,000
Product Warranty Expense		$ 22,000
Standard Product Warranty Accrual				$ 7,461	$ 7,544
Standard Product Warranty Accrual, Period Increase (Decrease)	$ 8,766
The UPRR [Member]
Product Liability Contingency [Line Items]
Concrete Ties Manufactured | item			1.6