Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue
Total net sales	$ 154,276	$ 167,094	$ 505,678	$ 462,438
Rail Products and Services
Disaggregation of Revenue
Total net sales	67,741	84,517	244,836	238,571
Rail Products and Services | Rail Products
Disaggregation of Revenue
Total net sales	39,224	49,234	153,420	139,600
Rail Products and Services | Rail Technologies
Disaggregation of Revenue
Total net sales	28,517	35,283	91,416	98,971
Construction Products
Disaggregation of Revenue
Total net sales	47,175	41,534	139,926	112,641
Construction Products | Piling and Fabricated Bridge
Disaggregation of Revenue
Total net sales	28,703	26,798	90,023	71,505
Construction Products | Precast Concrete Products
Disaggregation of Revenue
Total net sales	18,472	14,736	49,903	41,136
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	39,360	41,043	120,916	111,226
Tubular and Energy Services | Test, Inspection, and Threading Services
Disaggregation of Revenue
Total net sales	12,249	15,296	40,777	44,517
Tubular and Energy Services | Protective Coatings and Measurement Systems
Disaggregation of Revenue
Total net sales	$ 27,111	$ 25,747	$ 80,139	$ 66,709