Segment Information - Schedule of Segment ATOI to Consolidated Net Income (Loss) Attributable to Alcoa (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Total segment ATOI	$ 338	$ 224	$ 993	$ 783
Interest expense	(108)	(124)	(341)	(370)
Noncontrolling interests	20	(32)	12	(44)
Consolidated net income (loss) attributable to Alcoa	24	(143)	54	(51)
Unallocated Amounts (Net of Tax) [Member]
Segment Reporting Information [Line Items]
Impact of LIFO	9	(7)	12	12
Interest expense	(70)	(81)	(221)	(241)
Noncontrolling interests	(20)	32	(12)	44
Corporate expense	(74)	(62)	(212)	(195)
Restructuring and other charges	(108)	(2)	(324)	(19)
Other	$ (51)	$ (247)	$ (182)	$ (435)