Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue
Total net sales	$ 122,454	$ 118,702
Rail Products and Services
Disaggregation of Revenue
Total net sales	62,170	56,480
Rail Products and Services | Rail Products
Disaggregation of Revenue
Total net sales	36,034	34,365
Rail Products and Services | Rail Technologies
Disaggregation of Revenue
Total net sales	26,136	22,115
Construction Products
Disaggregation of Revenue
Total net sales	28,900	37,322
Construction Products | Piling and Fabricated Bridge
Disaggregation of Revenue
Total net sales	18,861	29,223
Construction Products | Precast Concrete Products
Disaggregation of Revenue
Total net sales	10,039	8,099
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	31,384	24,900
Tubular and Energy Services | Test, Inspection, and Threading
Disaggregation of Revenue
Total net sales	14,213	10,882
Tubular and Energy Services | Protective Coatings and Measurement Solutions
Disaggregation of Revenue
Total net sales	$ 17,171	$ 14,018