Revenue - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue
Total net sales	$ 128,775	$ 150,469
Rail Products and Services
Disaggregation of Revenue
Total net sales	70,204	75,694
Rail Products and Services | Rail Products
Disaggregation of Revenue
Total net sales	43,562	46,206
Rail Products and Services | Rail Technologies
Disaggregation of Revenue
Total net sales	26,642	29,488
Construction Products
Disaggregation of Revenue
Total net sales	29,034	37,345
Construction Products | Piling and Fabricated Bridge
Disaggregation of Revenue
Total net sales	18,391	23,732
Construction Products | Precast Concrete Products
Disaggregation of Revenue
Total net sales	10,643	13,613
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	29,537	37,430
Tubular and Energy Services | Test, Inspection, and Threading Services
Disaggregation of Revenue
Total net sales	9,704	14,724
Tubular and Energy Services | Protective Coatings and Measurement Systems
Disaggregation of Revenue
Total net sales	$ 19,833	$ 22,706