Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue
Total net sales	$ 200,933	$ 172,890	$ 351,402	$ 295,344
Rail Products and Services
Disaggregation of Revenue
Total net sales	101,401	91,884	177,095	154,054
Rail Products and Services | Rail Products
Disaggregation of Revenue
Total net sales	67,990	54,332	114,196	90,366
Rail Products and Services | Rail Technologies
Disaggregation of Revenue
Total net sales	33,411	37,552	62,899	63,688
Construction Products
Disaggregation of Revenue
Total net sales	55,406	42,207	92,751	71,107
Construction Products | Piling and Fabricated Bridge
Disaggregation of Revenue
Total net sales	37,588	25,846	61,320	44,707
Construction Products | Precast Concrete Products
Disaggregation of Revenue
Total net sales	17,818	16,361	31,431	26,400
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	44,126	38,799	81,556	70,183
Tubular and Energy Services | Test, Inspection, and Threading Services
Disaggregation of Revenue
Total net sales	13,804	15,008	28,528	29,221
Tubular and Energy Services | Protective Coatings and Measurement Systems
Disaggregation of Revenue
Total net sales	$ 30,322	$ 23,791	$ 53,028	$ 40,962