Segment Information - Schedule of Segment ATOI to Consolidated Net Income (Loss) Attributable to Alcoa (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Total segment ATOI	$ 418	$ 304	$ 743	$ 655
Interest expense	(105)	(118)	(225)	(233)
Noncontrolling interests	(9)	(29)	(28)	(8)
Consolidated net income (loss) attributable to Alcoa	138	(119)	(40)	30
Unallocated Amounts (Net of Tax) [Member]
Segment Reporting Information [Line Items]
Impact of LIFO	(8)	5	(15)	3
Interest expense	(69)	(76)	(147)	(151)
Noncontrolling interests	9	29	28	8
Corporate expense	(70)	(71)	(137)	(138)
Restructuring and other charges	(77)	(211)	(398)	(216)
Other	$ (65)	$ (99)	$ (114)	$ (131)