Business Segments (Reconciliation of Revenue from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information
Net Sales	$ 167,094	$ 131,492	$ 462,438	$ 395,054
Segment Profit (Loss)	11,176	9,118	27,837	19,485
Rail Products and Services
Segment Reporting Information
Net Sales	84,517	62,095	238,571	187,922
Segment Profit (Loss)	5,299	3,179	12,655	7,581
Construction Products
Segment Reporting Information
Net Sales	41,534	39,118	112,641	121,905
Segment Profit (Loss)	1,603	3,846	4,478	10,617
Tubular and Energy Services
Segment Reporting Information
Net Sales	41,043	30,279	111,226	85,227
Segment Profit (Loss)	$ 4,274	$ 2,093	$ 10,704	$ 1,287