Business Segment - Sales by Major Product Line (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from External Customer
Net Sales	$ 115,576	$ 118,365	$ 141,563	$ 121,907	$ 141,331	$ 144,848	$ 190,701	$ 139,548	$ 497,411	$ 616,428	$ 581,064
Rail Technologies and Services
Revenue from External Customer
Net Sales									276,447	321,808	319,524
Infrastructure Solutions
Revenue from External Customer
Net Sales									220,964	294,620	261,540
Rail Products | Rail Technologies and Services
Revenue from External Customer
Net Sales									186,263	208,145	203,054
Rail Technologies | Rail Technologies and Services
Revenue from External Customer
Net Sales									90,184	113,663	116,470
Fabricated Steel Products | Infrastructure Solutions
Revenue from External Customer
Net Sales									85,399	114,076	102,246
Precast Concrete Products | Infrastructure Solutions
Revenue from External Customer
Net Sales									63,308	68,410	56,407
Coatings and Measurement | Infrastructure Solutions
Revenue from External Customer
Net Sales									$ 72,257	$ 112,134	$ 102,887