Revenue - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue
Total net sales	$ 145,766	$ 200,933	$ 274,541	$ 351,402
Rail Products and Services
Disaggregation of Revenue
Total net sales	74,939	101,401	145,143	177,095
Rail Products and Services | Rail Products
Disaggregation of Revenue
Total net sales	52,206	67,990	95,768	114,196
Rail Products and Services | Rail Technologies
Disaggregation of Revenue
Total net sales	22,733	33,411	49,375	62,899
Construction Products
Disaggregation of Revenue
Total net sales	42,008	55,406	71,042	92,751
Construction Products | Piling and Fabricated Bridge
Disaggregation of Revenue
Total net sales	25,580	37,588	43,971	61,320
Construction Products | Precast Concrete Products
Disaggregation of Revenue
Total net sales	16,428	17,818	27,071	31,431
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	28,819	44,126	58,356	81,556
Tubular and Energy Services | Test, Inspection, and Threading Services
Disaggregation of Revenue
Total net sales	8,673	13,804	18,377	28,528
Tubular and Energy Services | Protective Coatings and Measurement Systems
Disaggregation of Revenue
Total net sales	$ 20,146	$ 30,322	$ 39,979	$ 53,028