Business Segments - Reconciliation of Revenue from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information
Total net sales	$ 130,053	$ 118,365	$ 400,655	$ 381,835
Operating Segments
Segment Reporting Information
Total net sales	130,053	118,365	400,655	381,835
Segment Profit	7,039	6,117	17,215	19,565
Rail Technologies and Services | Operating Segments
Segment Reporting Information
Total net sales	73,942	63,988	228,956	209,131
Segment Profit	3,555	3,742	12,050	10,729
Infrastructure Solutions
Segment Reporting Information
Total net sales	56,111	54,377	171,699	172,704
Infrastructure Solutions | Operating Segments
Segment Reporting Information
Total net sales	56,111	54,377	171,699	172,704
Segment Profit	$ 3,484	$ 2,375	$ 5,165	$ 8,836