Acquisitions (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			0 Months Ended				1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 30, 2014	Oct. 29, 2014	Jul. 07, 2014	Nov. 07, 2013	Feb. 28, 2014
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	$ 80,797	$ 37,500	$ 0
Business Acquisition, Transaction Costs	2,240	182
Chemtec [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired				66,719
Accrued post-closing purchase price adjustment				1,867
Business Combination, Indemnification Assets, Amount as of Acquisition Date				5,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net				68,909
FWO [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired					1,103
Accrued post-closing purchase price adjustment					161
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net					1,103
Carr Concrete Corporation [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired						12,480
Business Combination, Indemnification Assets, Amount as of Acquisition Date						1,000
Payments for Previous Acquisition						189
L.B. Foster Ball Winch, Inc. [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired							37,500
Business Combination, Indemnification Assets, Amount as of Acquisition Date							3,300
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net						12,480	37,995
Payments for Previous Acquisition								$ 495