Earnings Per Share - Reconciliation of Information Used to Compute Basic and Diluted EPS (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
Earnings Per Share [Abstract]
Net income (loss) attributable to Alcoa common shareholders	$ (119)	$ (2)	$ 30	$ 92
Less: preferred stock dividends declared			1	1
Net (loss) income available to common equity	(119)	(2)	29	91
Less: dividends and undistributed earnings allocated to participating securities
Net (loss) income available to Alcoa common shareholders - basic	(119)	(2)	29	91
Add: interest expense related to convertible notes			1
Net (loss) income available to Alcoa common shareholders - diluted	$ (119)	$ (2)	$ 29	$ 91
Average shares outstanding - basic	1,069	1,067	1,069	1,066
Stock options			2	4
Stock and performance awards			8	5
Convertible notes
Average shares outstanding - diluted	1,069	1,067	1,079	1,075