Segment Information (Schedule Of Segment Reporting Information To Consolidated Net Income Attributable To Alcoa) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Segment Reporting Information [Line Items]
Total segment ATOI	$ 296	$ 555
Interest expense	(123)	(111)
Noncontrolling interests	5	58
Discontinued operations		(1)
Consolidated net income attributable to Alcoa	94	308
Unallocated Amounts (Net Of Tax) [Member]
Segment Reporting Information [Line Items]
Impact of LIFO		(24)
Interest expense	(80)	(72)
Noncontrolling interests	(5)	(58)
Corporate expense	(64)	(67)
Restructuring and other charges	(7)	(6)
Discontinued operations		(1)
Other	$ (46)	$ (19)