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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Net income (loss) attributable to Alcoa common shareholders	$ 138	$ (119)	$ (40)	$ 30
Less: preferred stock dividends declared			1	1
Net income (loss) available to Alcoa common shareholders - basic	138	(119)	(41)	29
Add: interest expense related to convertible notes	0	0	0	0
Net income (loss) available to Alcoa common shareholders - diluted	$ 138	$ (119)	$ (41)	$ 29
Average shares outstanding - basic	1,173	1,069	1,137	1,069
Stock options	6			2
Stock and performance awards	10			8
Average shares outstanding - diluted	1,189	1,069	1,137	1,079