Business Segments - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information
Total net sales	$ 154,522	$ 141,563	$ 270,602	$ 263,470
Operating Segments
Segment Reporting Information
Total net sales	154,522	141,563	270,602	263,470
Segment Profit	8,310	10,672	10,176	13,448
Rail Technologies and Services | Operating Segments
Segment Reporting Information
Total net sales	88,782	74,939	155,014	145,143
Segment Profit	5,963	5,816	8,495	6,987
Infrastructure Solutions
Segment Reporting Information
Total net sales	65,740	66,624	115,588	118,327
Infrastructure Solutions | Operating Segments
Segment Reporting Information
Total net sales	65,740	66,624	115,588	118,327
Segment Profit	$ 2,347	$ 4,856	$ 1,681	$ 6,461