Segment and Geographical Area Information, Narrative (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017 productionfacilities	Jun. 30, 2016	Dec. 31, 2016 customer
Segment Reporting Information
Percentage of Employees Covered by Collective Bargaining Agreements	63.00%		63.00%
Percentage of Employees Covered by Collective Bargaining Agreements Expiring Within One Year	16.00%		16.00%
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	28.00%	27.00%	29.00%	26.00%
Customer Concentration Risk | Largest Customer | Accounts Receivable
Segment Reporting Information
Concentration Risk, Percentage			18.00%		18.00%
Customer Concentration Risk | Second Largest Customer | Sales Revenue, Net | Fabricated Products
Segment Reporting Information
Concentration Risk, Percentage	12.00%	10.00%	11.00%	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%