Summary of Significant Accounting Policies - Risks and Uncertainties and Use of Estimates (Details)	12 Months Ended
	Dec. 31, 2015 employee customer	Dec. 31, 2014 customer	Dec. 31, 2013 customer
Segment Reporting Information [Line Items]
Number of employees	9,200
Percent of employees located outside of the U.S.	15.00%
Percent of employees covered by collective bargaining agreements	50.00%
Sales Revenue [Member]
Segment Reporting Information [Line Items]
Number of customers | customer	0	0	0
Workforce Subject to Collective Bargaining Arrangements [Member] | Flat Rolled Products and High Performance Materials & Components [Member]
Segment Reporting Information [Line Items]
Number of employees	2,000