Derivative Financial Instruments and Related Hedging Programs, Hedging Discussion (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013 mmlbs	Sep. 30, 2012 mmlbs	Dec. 31, 2012	Sep. 30, 2013 Remainder of 2013 mmlbs	Sep. 30, 2013 2014 mmlbs	Sep. 30, 2013 2015 mmlbs	Mar. 29, 2010 Convertible Notes
Derivative Financial Instruments and Related Hedging Programs (Textuals) [Abstract]
Aggregate fair value of derivative instruments that contain credit-risk-related contingency features that were in a net liability position	$ 4.6
Total fabricated products shipments containing fixed price terms	87.2	139.0
Firm price customer sales contracts containing price risk on anticipated purchases of primary aluminum				37.3	19.0	1.3
Principal amount of notes	$ 225.0		$ 225.0				$ 175.0