Contingencies And Commitments (Litigation) (Narrative) (Details) (USD $) In Millions, unless otherwise specified			1 Months Ended	12 Months Ended	0 Months Ended
	Nov. 08, 2011 days	May 31, 2011 Breaches Of Warranty [Member]	Nov. 30, 2006 Curtis V. Alcoa Inc. [Member] days	Dec. 31, 2011 SCRG, Brownfield Recovery Corp., Energy Answers Corporation Of Puerto Rico [Member]	Jan. 20, 2011 SCRG, Brownfield Recovery Corp., Energy Answers Corporation Of Puerto Rico [Member] Breaches Of Warranty [Member]	Jan. 20, 2011 SCRG, Brownfield Recovery Corp., Energy Answers Corporation Of Puerto Rico [Member] Punitive Damages [Member]	Jan. 20, 2011 SCRG, Brownfield Recovery Corp., Energy Answers Corporation Of Puerto Rico [Member] Property Damages [Member]	Feb. 27, 2008 Aluminium Bahrain B.S.C. V. Alcoa Inc. [Member] years
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
Damages awarded to plaintiff					$ 13	$ 6	$ 10
Post-trial litigation charge recorded				20
Damages awarded to plaintiff, pre-judgment interest		$ 2