Revenue - Timing of Transfer (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue
Total net sales	$ 145,766	$ 200,933	$ 274,541	$ 351,402
Point in time
Disaggregation of Revenue
Total net sales	110,220	152,338	206,218	261,059
Over time
Disaggregation of Revenue
Total net sales	35,546	48,595	68,323	90,343
Rail Products and Services
Disaggregation of Revenue
Total net sales	74,939	101,401	145,143	177,095
Rail Products and Services | Point in time
Disaggregation of Revenue
Total net sales	61,275	80,701	116,163	137,193
Rail Products and Services | Over time
Disaggregation of Revenue
Total net sales	13,664	20,700	28,980	39,902
Construction Products
Disaggregation of Revenue
Total net sales	42,008	55,406	71,042	92,751
Construction Products | Point in time
Disaggregation of Revenue
Total net sales	28,148	38,095	45,031	61,190
Construction Products | Over time
Disaggregation of Revenue
Total net sales	13,860	17,311	26,011	31,561
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	28,819	44,126	58,356	81,556
Tubular and Energy Services | Point in time
Disaggregation of Revenue
Total net sales	20,797	33,542	45,024	62,676
Tubular and Energy Services | Over time
Disaggregation of Revenue
Total net sales	$ 8,022	$ 10,584	$ 13,332	$ 18,880