Business Segments (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011 Customer 1 - 10% of Sales [Member] Rail Products And Construction Products [Member]
Segment Reporting Information [Line Items]
Entity-Wide Revenue, Major Customer, Percentage		10.00%
Entity-Wide Revenue, Major Customer, Amount		$ 58,715
Segment Reporting, Factors Used to Identify Entity's Reportable Segments	L.B. Foster Company is organized and evaluated by product group, which is the basis for identifying reportable segments.The Company is engaged in the manufacture, fabrication and distribution of rail, construction and tubular products.The Company's Rail segment provides a full line of new and used rail, trackwork and accessories to railroads, mines and industry. The Rail segment also designs and produces concrete railroad ties, insulated rail joints, power rail, track fasteners, coverboards and special accessories for mass transit and other rail systems. The Company also engineers, manufactures and assembles friction management products and railway wayside data collection and management systems. The Company's Construction segment sells and rents steel sheet piling, H-bearing pile, and other piling products for foundation and earth retention requirements. In addition, the Company's Fabricated Products division sells bridge decking, bridge railing, structural steel fabrications, expansion joints and other products for highway construction and repair. The Buildings division produces precast concrete buildings.The Company's Tubular segment supplies pipe coatings for natural gas pipelines and utilities. Additionally, this segment produces threaded pipe products for industrial water well and irrigation markets. The Company markets its products directly in all major industrial areas of the United States, Canada and the United Kingdom, primarily through an internal sales force
Segment Reporting, Measurement for Transactions Between Reportable Segments	The following table illustrates net sales, profits, assets, depreciation/amortization and expenditures for long-lived assets of the Company by segment from continuing operating activities. Segment profit is the earnings from continuing operating activities before income taxes and includes internal cost of capital charges for assets used in the segment at a rate of, generally 1% per month. The accounting policies of the reportable segments are the same as those described in the summary of significant accounting policies except that the Company accounts for inventory on a First-In, First-Out (FIFO) basis at the segment level compared to a Last-In, First-Out (LIFO) basis at the consolidated level