Revenue (Timing of Transfer) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue
Total net sales	$ 626,969	$ 536,377
Point in time
Disaggregation of Revenue
Total net sales	463,716	403,039
Over time
Disaggregation of Revenue
Total net sales	163,253	133,338
Rail Products and Services
Disaggregation of Revenue
Total net sales	319,524	256,127
Rail Products and Services | Point in time
Disaggregation of Revenue
Total net sales	232,814	205,942
Rail Products and Services | Over time
Disaggregation of Revenue
Total net sales	86,710	50,185
Construction Products
Disaggregation of Revenue
Total net sales	158,653	161,801
Construction Products | Point in time
Disaggregation of Revenue
Total net sales	106,168	97,462
Construction Products | Over time
Disaggregation of Revenue
Total net sales	52,485	64,339
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	148,792	118,449
Tubular and Energy Services | Point in time
Disaggregation of Revenue
Total net sales	124,734	99,635
Tubular and Energy Services | Over time
Disaggregation of Revenue
Total net sales	$ 24,058	$ 18,814