Derivative Financial Instruments and Related Hedging Programs (Details Textual) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2011 mmlbs	Jun. 30, 2010 mmlbs	Dec. 31, 2010	Mar. 31, 2010
Derivative Financial Instruments and Related Hedging Programs (Textuals) [Abstract]
Total fabricated products shipments containing fixed price terms	61.1	47.8
Aggregate principal amount of notes	$ 175.0		$ 175.0	$ 175.0
Remainder of current year [Member]
Derivative Financial Instruments and Related Hedging Programs (Textuals) [Abstract]
Firm price customer sales contracts containing price risk on anticipated purchases of primary aluminum	81.1
Percentage Of Natural Gas Purchases For Which The Companys Exposure To Fluctuations In Gas Prices Have Been Reduced	93.00%
Year Two And There After [Member]
Derivative Financial Instruments and Related Hedging Programs (Textuals) [Abstract]
Firm price customer sales contracts containing price risk on anticipated purchases of primary aluminum	0.4
Percentage Of Natural Gas Purchases For Which The Companys Exposure To Fluctuations In Gas Prices Have Been Reduced	32.00%
Year One [Member]
Derivative Financial Instruments and Related Hedging Programs (Textuals) [Abstract]
Firm price customer sales contracts containing price risk on anticipated purchases of primary aluminum	15.3
Percentage Of Natural Gas Purchases For Which The Companys Exposure To Fluctuations In Gas Prices Have Been Reduced	74.00%