Revenue - Timing of Transfer (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue
Total net sales (Note 4)	$ 513,620	$ 497,411
Point in time
Disaggregation of Revenue
Total net sales (Note 4)	359,989	351,391
Over time
Disaggregation of Revenue
Total net sales (Note 4)	153,631	146,020
Rail, Technologies, and Services
Disaggregation of Revenue
Total net sales (Note 4)	299,749	276,447
Rail, Technologies, and Services | Point in time
Disaggregation of Revenue
Total net sales (Note 4)	232,880	212,212
Rail, Technologies, and Services | Over time
Disaggregation of Revenue
Total net sales (Note 4)	66,869	64,235
Precast Concrete Products
Disaggregation of Revenue
Total net sales (Note 4)	70,990	63,314
Precast Concrete Products | Point in time
Disaggregation of Revenue
Total net sales (Note 4)	21,351	20,443
Precast Concrete Products | Over time
Disaggregation of Revenue
Total net sales (Note 4)	49,639	42,871
Steel Products and Measurement
Disaggregation of Revenue
Total net sales (Note 4)	142,881	157,650
Steel Products and Measurement | Point in time
Disaggregation of Revenue
Total net sales (Note 4)	105,758	118,736
Steel Products and Measurement | Over time
Disaggregation of Revenue
Total net sales (Note 4)	$ 37,123	$ 38,914