Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue
Total net sales	$ 626,969	$ 536,377
Rail Products and Services
Disaggregation of Revenue
Total net sales	319,524	256,127
Rail Products and Services | Rail Products
Disaggregation of Revenue
Total net sales	188,590	155,870
Rail Products and Services | Rail Technologies
Disaggregation of Revenue
Total net sales	130,934	100,257
Construction Products
Disaggregation of Revenue
Total net sales	158,653	161,801
Construction Products | Piling and Fabricated Bridge
Disaggregation of Revenue
Total net sales	102,246	105,924
Construction Products | Precast Concrete Products
Disaggregation of Revenue
Total net sales	56,407	55,877
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	148,792	118,449
Tubular and Energy Services | Test Inspection and Threading
Disaggregation of Revenue
Total net sales	59,766	50,683
Tubular and Energy Services | Protective Coating and Measurements Systems
Disaggregation of Revenue
Total net sales	$ 89,026	$ 67,766