Segment Information - Schedule of Segment Reporting Information to Consolidated Net Income Attributable to Alcoa (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Segment Reporting Information [Line Items]
Total segment ATOI	$ 235		$ 462		$ 806		$ 1,652
Interest expense	(124)		(125)		(370)		(399)
Noncontrolling interests	32		(53)		44		(166)
Discontinued operations							(5)
Consolidated net (loss) income attributable to Alcoa	(143)		172		(51)		802
Environmental remediation charges	116				129
Civil litigation matter	26				55
Unallocated Amounts (Net Of Tax) [Member]
Segment Reporting Information [Line Items]
Impact of LIFO	(7)		2		12		(49)
Interest expense	(81)		(81)		(241)		(259)
Noncontrolling interests	32		(53)		44		(166)
Corporate expense	(62)		(76)		(195)		(219)
Restructuring and other charges	(2)		(7)		(19)		(35)
Discontinued operations							(5)
Other*	$ (258)	[1]	$ (75)	[1]	$ (458)	[1]	$ (117)	[1]

[1] In the third quarter and nine-month period of 2012, Other includes after-tax charges related to environmental remediation ($116 and $129) and a civil litigation matter ($26 and $55), respectively, (see Note G).