Revenue - Timing of Transfer (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
Point in time
Disaggregation of Revenue
Total net sales									468,282	463,716
Over time
Disaggregation of Revenue
Total net sales									186,775	163,253
Rail Products and Services
Disaggregation of Revenue
Total net sales									321,808	319,524
Rail Products and Services | Point in time
Disaggregation of Revenue
Total net sales									240,047	232,814
Rail Products and Services | Over time
Disaggregation of Revenue
Total net sales									81,761	86,710
Construction Products
Disaggregation of Revenue
Total net sales									182,486	158,653
Construction Products | Point in time
Disaggregation of Revenue
Total net sales									115,590	106,168
Construction Products | Over time
Disaggregation of Revenue
Total net sales									66,896	52,485
Tubular and Energy Services
Disaggregation of Revenue
Total net sales									150,763	148,792
Tubular and Energy Services | Point in time
Disaggregation of Revenue
Total net sales									112,645	124,734
Tubular and Energy Services | Over time
Disaggregation of Revenue
Total net sales									$ 38,118	$ 24,058