Schedule Of Segment Reporting Information To Consolidated Net Income Attributable To Alcoa (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting Information [Line Items]
Total segment ATOI	$ 275	$ 635	$ 571	$ 1,190
Interest expense	(123)	(163)	(246)	(274)
Noncontrolling interests	17	(55)	12	(113)
Discontinued operations		(4)		(5)
Consolidated net (loss) income attributable to Alcoa	(2)	322	92	630
Unallocated Amounts (Net Of Tax)
Segment Reporting Information [Line Items]
Impact of LIFO	19	(27)	19	(51)
Interest expense	(80)	(106)	(160)	(178)
Noncontrolling interests	17	(55)	12	(113)
Corporate expense	(69)	(76)	(133)	(143)
Restructuring and other charges	(10)	(22)	(17)	(28)
Discontinued operations		(4)		(5)
Other	$ (154)	$ (23)	$ (200)	$ (42)

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