Revenue - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue
Total net sales	$ 116,080	$ 121,907
Rail Technologies and Services
Disaggregation of Revenue
Total net sales	66,232	70,204
Rail Technologies and Services \| Rail Products
Disaggregation of Revenue
Total net sales	43,810	47,899
Rail Technologies and Services \| Rail Technologies
Disaggregation of Revenue
Total net sales	22,422	22,305
Infrastructure Solutions
Disaggregation of Revenue
Total net sales	49,848	51,703
Infrastructure Solutions \| Fabricated Steel Products
Disaggregation of Revenue
Total net sales	27,721	18,391
Infrastructure Solutions \| Precast Concrete Products
Disaggregation of Revenue
Total net sales	12,678	10,643
Infrastructure Solutions \| Coatings and Measurement
Disaggregation of Revenue
Total net sales	$ 9,449	$ 22,669

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 41
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
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-Section S99
-Paragraph 1
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+ Details