Business Segments - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information
Total net sales	$ 116,080	$ 121,907
Operating Segments
Segment Reporting Information
Total net sales	116,080	121,907
Segment Profit (Loss)	1,866	2,775
Rail Technologies and Services | Operating Segments
Segment Reporting Information
Total net sales	66,232	70,204
Segment Profit (Loss)	2,532	1,171
Infrastructure Solutions
Segment Reporting Information
Total net sales	49,848	51,703
Infrastructure Solutions | Operating Segments
Segment Reporting Information
Total net sales	49,848	51,703
Segment Profit (Loss)	$ (666)	$ 1,604