Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue
Total net sales	$ 149,379	$ 154,276	$ 200,933	$ 150,469	$ 164,531	$ 167,094	$ 172,890	$ 122,454	$ 655,057	$ 626,969
Rail Products and Services
Disaggregation of Revenue
Total net sales									321,808	319,524
Rail Products and Services | Rail Products
Disaggregation of Revenue
Total net sales									194,464	188,590
Rail Products and Services | Rail Technologies
Disaggregation of Revenue
Total net sales									127,344	130,934
Construction Products
Disaggregation of Revenue
Total net sales									182,486	158,653
Construction Products | Piling and Fabricated Bridge
Disaggregation of Revenue
Total net sales									114,076	102,246
Construction Products | Precast Concrete Products
Disaggregation of Revenue
Total net sales									68,410	56,407
Tubular and Energy Services
Disaggregation of Revenue
Total net sales									150,763	148,792
Tubular and Energy Services | Test Inspection and Threading
Disaggregation of Revenue
Total net sales									51,003	59,766
Tubular and Energy Services | Protective Coating and Measurements Systems
Disaggregation of Revenue
Total net sales									$ 99,760	$ 89,026