Business, Product and Geographical Area Information and Concentration of Risk - Narrative (Details)	12 Months Ended
	Dec. 31, 2018 productionfacilities customer	Dec. 31, 2017 customer	Dec. 31, 2016 customer
Segment Reporting Information
Percentage of Employees Covered by Collective Bargaining Agreements	62.00%
Percentage of Employees Covered by Collective Bargaining Agreements Expiring Within One Year	0.00%
United States
Segment Reporting Information
Number of production facilities	12
Canada
Segment Reporting Information
Number of production facilities	1
Customer Concentration Risk [Member] | Net sales | Largest Customer [Member] | Fabricated Products
Segment Reporting Information
Concentration risk, percentage	25.00%	27.00%	26.00%
Number of Customers | customer	1	1	1
Customer Concentration Risk [Member] | Net sales | Second Largest Customer [Member] | Fabricated Products
Segment Reporting Information
Concentration risk, percentage	15.00%	12.00%	10.00%
Customer Concentration Risk [Member] | Trade receivables | Largest Customer [Member]
Segment Reporting Information
Concentration risk, percentage	31.00%	22.00%
Customer Concentration Risk [Member] | Trade receivables | Second Largest Customer [Member]
Segment Reporting Information
Concentration risk, percentage	11.00%	14.00%