Segment Information - Schedule of Segment ATOI to Consolidated Net Income Attributable to Alcoa (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Total segment ATOI	$ 304	$ 255	$ 655	$ 559
Interest expense	(118)	(123)	(233)	(246)
Noncontrolling interests	(29)	(17)	(8)	(12)
Consolidated net (loss) income attributable to Alcoa	(119)	(2)	30	92
Unallocated Amounts (Net of Tax) [Member]
Segment Reporting Information [Line Items]
Impact of LIFO	5	19	3	19
Interest expense	(76)	(80)	(151)	(160)
Noncontrolling interests	29	17	8	12
Corporate expense	(71)	(69)	(138)	(133)
Restructuring and other charges	(211)	(10)	(216)	(17)
Other	$ (99)	$ (134)	$ (131)	$ (188)