Acquisitions (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired	$ 12,786
L.B. Foster Ball Winch, Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Name of Acquired Entity		Ball Winch, LLC (Ball Winch).
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		37,995
Payments for Previous Acquisition	495
Carr Concrete Corporation [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Jul. 07, 2014
Business Acquisition, Name of Acquired Entity	Carr Concrete Corporation (Carr)
Payments to Acquire Businesses, Net of Cash Acquired	12,491
Accrued post-closing purchase price adjustment	200
Business Combination, Indemnification Assets, Amount as of Acquisition Date	1,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net	$ 12,491