Earnings Per Share - Reconciliation of Information Used to Compute Basic and Diluted EPS (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share [Abstract]
Net (loss) income attributable to Alcoa common shareholders	$ (178)	$ 149
Less: preferred stock dividends declared	1	1
Net (loss) income available to Alcoa common shareholders - basic	(179)	148
Add: interest expense related to convertible notes		8
Net (loss) income available to Alcoa common shareholders - diluted	$ (179)	$ 156
Average shares outstanding - basic	1,101	1,069
Stock options		3
Stock and performance awards		8
Convertible notes		89
Average shares outstanding - diluted	1,101	1,169