Business Segments (Reconciliation of Revenue from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information
Net Sales	$ 172,890	$ 144,860	$ 295,344	$ 263,562
Segment Profit	12,710	8,558	16,661	10,367
Rail Products and Services
Segment Reporting Information
Net Sales	91,884	69,347	154,054	125,827
Segment Profit	5,308	3,579	7,356	4,402
Construction Products
Segment Reporting Information
Net Sales	42,207	45,465	71,107	82,787
Segment Profit	2,857	5,105	2,875	6,771
Tubular and Energy Services
Segment Reporting Information
Net Sales	38,799	30,048	70,183	54,948
Segment Profit	$ 4,545	$ (126)	$ 6,430	$ (806)