Business Segments (Reconciliation of Revenue from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information
Total net sales	$ 150,469	$ 122,454
Segment Profit	9,001	3,951
Rail Products and Services
Segment Reporting Information
Total net sales	75,694	62,170
Construction Products
Segment Reporting Information
Total net sales	37,345	28,900
Tubular and Energy Services
Segment Reporting Information
Total net sales	37,430	31,384
Operating Segments
Segment Reporting Information
Total net sales	150,469	122,454
Segment Profit	9,001	3,951
Operating Segments | Rail Products and Services
Segment Reporting Information
Total net sales	75,694	62,170
Segment Profit	3,479	2,048
Operating Segments | Construction Products
Segment Reporting Information
Total net sales	37,345	28,900
Segment Profit	834	18
Operating Segments | Tubular and Energy Services
Segment Reporting Information
Total net sales	37,430	31,384
Segment Profit	$ 4,688	$ 1,885