Business Segments (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Net	$ 156,458	$ 162,248	$ 149,936	$ 129,321	$ 140,724	$ 170,346	[1]	$ 163,180	[2]	$ 114,291	$ 597,963	$ 588,541	$ 575,337
Segment Reporting, Factors Used to Identify Entity's Reportable Segments											The Company is a leading manufacturer, fabricator, and distributor of products and services for rail, construction, energy and utility markets. The Company is organized and evaluated by product group, which is the basis for identifying reportable segments. Each segment represents a revenue-producing component of the Company for which separate financial information is produced internally and is subject to evaluation by the Company's chief operating decision maker in deciding how to allocate resources. Each segment is evaluated based upon their contribution to the Company's consolidated results based upon segment profit. 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.The Company's Rail Products 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. In addition, the Rail Products segment also engineers, manufactures and assembles friction management products and railway wayside data collection and management systems. The Company's Construction Products 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, bridge forms and other products for highway construction and repair. The Buildings division produces precast concrete buildings.The Company's Tubular Products segment supplies pipe coatings for natural gas pipelines and utilities. Additionally, this segment produces threaded pipe products for industrial water well and irrigation markets. L.B. Foster Ball Winch, Inc., which was acquired on November 7, 2013, will enhance our pipe coating capabilities and expand our business into the field service coating space.
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 operations. Segment profit is the earnings from continuing operations before income taxes and includes internal cost of capital charges for net assets used in the segment at a rate of generally 1% per month. The internal cost of capital charges are eliminated during the consolidation process. 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
Rail Products Segment [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Net											363,667	370,322	315,133
Construction Products Segment [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Net											191,751	169,253	227,734
Tubular Products Segments [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Net											42,545	48,966	32,470
Customer 1 - 10% of Sales [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage													10.00%
Customer 1 - 10% of Sales [Member] | Rail Products And Construction Products [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Goods, Net													$ 58,715

[1] Includes a pre-tax loss of approximately $315 from the Company’s sale of Precise.

[2] Includes a pre-tax gain of approximately $3,508 from the Company’s sale of SSD.