Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue
Total net sales	$ 150,469	$ 122,454
Rail Products and Services
Disaggregation of Revenue
Total net sales	75,694	62,170
Rail Products and Services | Rail Products
Disaggregation of Revenue
Total net sales	46,206	36,034
Rail Products and Services | Rail Technologies
Disaggregation of Revenue
Total net sales	29,488	26,136
Construction Products
Disaggregation of Revenue
Total net sales	37,345	28,900
Construction Products | Piling and Fabricated Bridge
Disaggregation of Revenue
Total net sales	23,732	18,861
Construction Products | Precast Concrete Products
Disaggregation of Revenue
Total net sales	13,613	10,039
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	37,430	31,384
Tubular and Energy Services | Test, Inspection, and Threading Services
Disaggregation of Revenue
Total net sales	14,724	14,213
Tubular and Energy Services | Protective Coatings and Measurement Systems
Disaggregation of Revenue
Total net sales	$ 22,706	$ 17,171