Revenue - Timing of Transfer (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue
Total net sales	$ 118,365	$ 144,848	$ 381,835	$ 475,097
Point in time
Disaggregation of Revenue
Total net sales	80,249	93,329	275,396	333,235
Over time
Disaggregation of Revenue
Total net sales	38,116	51,519	106,439	141,862
Rail Products and Services
Disaggregation of Revenue
Total net sales	63,988	67,741	209,131	244,836
Rail Products and Services | Point in time
Disaggregation of Revenue
Total net sales	47,027	46,712	163,190	183,905
Rail Products and Services | Over time
Disaggregation of Revenue
Total net sales	16,961	21,029	45,941	60,931
Construction Products
Disaggregation of Revenue
Total net sales	37,883	47,175	108,925	139,926
Construction Products | Point in time
Disaggregation of Revenue
Total net sales	22,928	29,375	67,959	90,565
Construction Products | Over time
Disaggregation of Revenue
Total net sales	14,955	17,800	40,966	49,361
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	16,494	29,932	63,779	90,335
Tubular and Energy Services | Point in time
Disaggregation of Revenue
Total net sales	10,294	17,242	44,247	58,765
Tubular and Energy Services | Over time
Disaggregation of Revenue
Total net sales	$ 6,200	$ 12,690	$ 19,532	$ 31,570