Commitments and Contingent Liabilites (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Product Liability Contingency [Line Items]
Standard Product Warranty Accrual	$ 11,500				$ 7,483				$ 11,500	$ 7,483	$ 15,727
Sales Revenue, Goods, Net	161,149	167,797	166,832	111,414	156,458	162,248	149,936	129,321	607,192	597,963	588,541
Property, Plant and Equipment, Net	74,802				50,109				74,802	50,109
Tucson, AZ [Member]
Product Liability Contingency [Line Items]
Sales Revenue, Goods, Net									15,297	12,664	25,441
Property, Plant and Equipment, Net	978								978
Reserve for Concrete Ties [Member]
Product Liability Contingency [Line Items]
Litigation Settlement, Amount											12,000
Product Warranty Expense											22,000
Standard Product Warranty Accrual	10,331				6,462				10,331	6,462
Standard Product Warranty Accrual, Period Increase (Decrease)	4,766		4,000						9,854	612	23,019
Reserve for Environmental Costs [Member]
Product Liability Contingency [Line Items]
Accrual for Environmental Loss Contingencies	$ 3,344				$ 2,190				$ 3,344	$ 2,190