Contingencies And Commitments (Litigation) (Narrative) (Details) In Millions, unless otherwise specified				0 Months Ended		1 Months Ended	12 Months Ended	0 Months Ended
	Mar. 31, 2012 USD ($)	Mar. 31, 2012 EUR (€)	Nov. 08, 2011 D	May 31, 2011 Negligence Award [Member] USD ($)	May 31, 2011 Breaches Of Warranty [Member] USD ($)	Nov. 30, 2006 Curtis v. Alcoa Inc. [Member] D employee	Dec. 31, 2011 St. Croix Renaissance Group, L.L.L.P. (SCRG), Brownfield Recovery Corp., And Energy Answers Corporation Of Puerto Rico [Member] USD ($)	Jan. 20, 2011 St. Croix Renaissance Group, L.L.L.P. (SCRG), Brownfield Recovery Corp., And Energy Answers Corporation Of Puerto Rico [Member] Breaches Of Warranty [Member] USD ($)	Jan. 20, 2011 St. Croix Renaissance Group, L.L.L.P. (SCRG), Brownfield Recovery Corp., And Energy Answers Corporation Of Puerto Rico [Member] Punitive Damages [Member] USD ($)	Jan. 20, 2011 St. Croix Renaissance Group, L.L.L.P. (SCRG), Brownfield Recovery Corp., And Energy Answers Corporation Of Puerto Rico [Member] Property Damages [Member] USD ($)	Feb. 27, 2008 Aluminium Bahrain B.S.C. (Alba) [Member] Y
Loss Contingencies [Line Items]
Period of alleged conspiracy, years											15
Number of days required to dismiss lawsuit			30
Retired former employees involved in class action						13,000
Trial length, number of days						8
Management estimate for maximum exposure from class action	$ 115	€ 85
Damages awarded to plaintiff								13	6	10
Post-trial litigation charge recorded							20
Damages awarded to plaintiff, pre-judgment interest					2
Court granted motion for judgment				$ 10