Revenue (Timing of Transfer) (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
Point in time
Disaggregation of Revenue
Total net sales	102,757	122,359	363,816	346,005
Over time
Disaggregation of Revenue
Total net sales	51,519	44,735	141,862	116,433
Rail Products and Services
Disaggregation of Revenue
Total net sales	67,741	84,517	244,836	238,571
Rail Products and Services | Point in time
Disaggregation of Revenue
Total net sales	46,712	61,426	183,905	176,592
Rail Products and Services | Over time
Disaggregation of Revenue
Total net sales	21,029	23,091	60,931	61,979
Construction Products
Disaggregation of Revenue
Total net sales	47,175	41,534	139,926	112,641
Construction Products | Point in time
Disaggregation of Revenue
Total net sales	29,375	27,459	90,565	74,581
Construction Products | Over time
Disaggregation of Revenue
Total net sales	17,800	14,075	49,361	38,060
Tubular and Energy Services
Disaggregation of Revenue
Total net sales	39,360	41,043	120,916	111,226
Tubular and Energy Services | Point in time
Disaggregation of Revenue
Total net sales	26,670	33,474	89,346	94,832
Tubular and Energy Services | Over time
Disaggregation of Revenue
Total net sales	$ 12,690	$ 7,569	$ 31,570	$ 16,394