Segment Information - Schedule of Segment ATOI to Consolidated Net Income Attributable to Alcoa (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Total segment ATOI	$ 351	$ 304
Interest expense	(115)	(123)
Noncontrolling interests	(21)	(5)
Consolidated net income attributable to Alcoa	149	94
Unallocated amounts (net of tax) [Member]
Segment Reporting Information [Line Items]
Impact of LIFO	(2)
Interest expense	(75)	(80)
Noncontrolling interests	(21)	(5)
Corporate expense	(67)	(64)
Restructuring and other charges	(5)	(7)
Other	$ (32)	$ (54)