Restructuring And Other Charges (Activity And Reserve Balances For Restructuring Charges) (Details) (USD $) In Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2011		Dec. 31, 2010		Dec. 31, 2009
Cash payments	$ (38)		$ (108)
Restructuring charges	32		96
Other	(13)	[1]	(98)	[1]
Restructuring reserve balance	97		116		226
Layoff Costs [Member]
Cash payments	(32)		(93)
Restructuring charges	31		43
Other	(13)	[1]	(57)	[1]
Restructuring reserve balance	39		53		160
Other Exit Costs [Member]
Cash payments	(6)		(15)
Restructuring charges	1		53
Other			(41)	[1]
Restructuring reserve balance	$ 58		$ 63		$ 66

[1] Other includes reversals of previously recorded restructuring charges and the effects of foreign currency translation. In 2010, Other for other exit costs also included a reclassification of the following restructuring charges: $30 in asset retirement and $14 in environmental obligations, as these liabilities are included in Alcoa's separate reserves for asset retirement obligations and environmental remediation, respectively.