Business Segments (Reconciliation of Revenue from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information
Total net sales	$ 200,933	$ 172,890	$ 351,402	$ 295,344
Segment Profit	16,351	12,710	25,352	16,661
Rail Products and Services
Segment Reporting Information
Total net sales	101,401	91,884	177,095	154,054
Construction Products
Segment Reporting Information
Total net sales	55,406	42,207	92,751	71,107
Tubular and Energy Services
Segment Reporting Information
Total net sales	44,126	38,799	81,556	70,183
Operating Segments
Segment Reporting Information
Total net sales	200,933	172,890	351,402	295,344
Segment Profit	16,351	12,710	25,352	16,661
Operating Segments | Rail Products and Services
Segment Reporting Information
Total net sales	101,401	91,884	177,095	154,054
Segment Profit	7,919	5,308	11,398	7,356
Operating Segments | Construction Products
Segment Reporting Information
Total net sales	55,406	42,207	92,751	71,107
Segment Profit	3,413	2,857	4,247	2,875
Operating Segments | Tubular and Energy Services
Segment Reporting Information
Total net sales	44,126	38,799	81,556	70,183
Segment Profit	$ 5,019	$ 4,545	$ 9,707	$ 6,430