Segment and Geographical Area Information, Narrative (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017 productionfacilities	Sep. 30, 2016	Dec. 31, 2016 customer
Segment Reporting Information
Percentage of Employees Covered by Collective Bargaining Agreements	64.00%		64.00%
Percentage of Employees Covered by Collective Bargaining Agreements Expiring Within One Year	12.00%		12.00%
Domestic
Segment Reporting Information
Number of production facilities			11
Foreign
Segment Reporting Information
Number of production facilities			1
Customer Concentration Risk | Largest Customer | Sales Revenue, Net | Fabricated Products
Segment Reporting Information
Concentration Risk, Percentage	27.00%	25.00%	28.00%	26.00%
Customer Concentration Risk | Largest Customer | Accounts Receivable
Segment Reporting Information
Concentration Risk, Percentage			17.00%		18.00%
Customer Concentration Risk | Second Largest Customer | Sales Revenue, Net | Fabricated Products
Segment Reporting Information
Concentration Risk, Percentage	11.00%	11.00%	10.00%	10.00%
Customer Concentration Risk | Second Largest Customer | Accounts Receivable
Segment Reporting Information
Concentration Risk, Percentage			16.00%		12.00%
Customer Concentration Risk | Second Largest Customer | Accounts Receivable | Fabricated Products
Segment Reporting Information
Number of Customers | customer					2
Customer Concentration Risk | Second Largest Customer (number 2) | Accounts Receivable
Segment Reporting Information
Concentration Risk, Percentage					12.00%