Retirement Plans (Other Post-Retirement Retirement Plan) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
General Discussion of Pension and Other Postretirement Benefits	The Company has seven retirement plans which cover its hourly and salaried employees in the United States: three defined benefit plans (one active / two frozen) and four defined contribution plans. Employees are eligible to participate in the appropriate plan based on employment classification. The Company's contributions to the defined benefit and defined contribution plans are governed by the Employee Retirement Income Security Act of 1974 ("ERISA"), policy and investment guidelines of the applicable plan. The Company's policy is to contribute at least the minimum in accordance with the funding standards of ERISA.The Company's subsidiary, L.B. Foster Rail Technologies ("Rail Technologies"), maintains two defined contribution plans for its employees in Canada, as well as a post-retirement benefit plan. In the United Kingdom, Rail Technologies maintains two defined contribution plans and a defined benefit plan. These plans are discussed in further detail below
Other Post-Retirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
General Discussion of Pension and Other Postretirement Benefits	Rail Technologies' operation near Montreal, Quebec, Canada, maintains a post-retirement benefit plan, which provides retiree life insurance, health care benefits, and, for a closed group of employees, dental care. Retiring employees with a minimum of 10 years of service are eligible for the plan benefits. The plan is not funded. Cost of benefits earned by employees is charged to expense as services are rendered. The expense related to this plan was not material for 2015 and 2014. Rail Technologies' accrued benefit obligation was $823 and $1,172 as of December 31, 2015 and 2014, respectively. This obligation is recognized within other long-term liabilities. Benefit payments anticipated for 2016 are not material.
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent	$ 823	$ 1,172
Projected benefit obligation: Discount rate	4.20%	4.00%
Weighted average health care trend rate	5.00%	6.20%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	4.40%
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent	$ 3,524	$ 3,720
UNITED KINGDOM
Defined Benefit Plan Disclosure [Line Items]
General Discussion of Pension and Other Postretirement Benefits	The Portec Rail Products (UK) Limited Pension Plan covers certain current employees, former employees, and retirees. The plan has been frozen to new entrants since April 1, 1997 and also covers the former employees of a merged plan after January 2002. Benefits under the plan were based on years of service and eligible compensation during defined periods of service. Our funding policy for the plan is to make minimum annual contributions required by applicable regulations
Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent	$ 1,201	$ 2,040
Projected benefit obligation: Discount rate	4.00%	3.60%	4.60%