Earnings Per Share (Reconciliation Of Information Used To Compute Basic And Diluted EPS) (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Earnings Per Share
Income (loss) from continuing operations attributable to Alcoa common shareholders	$ 326	$ 137	$ 635	$ (57)
Less: preferred stock dividends declared			1	1
Income (loss) from continuing operations available to common equity	326	137	634	(58)
Less: dividends and undistributed earnings allocated to participating securities	1	1	2
Income (loss) from continuing operations available to Alcoa common shareholders - basic	325	136	632	(58)
Add: interest expense related to convertible notes	8	8	15
Income (loss) from continuing operations available to Alcoa common shareholders - diluted	$ 333	$ 144	$ 647	$ (58)
Average shares outstanding - basic	1,064	1,021	1,058	1,014
Stock options	9	6	9
Stock and performance awards	3	1	3
Convertible notes	89	89	89
Average shares outstanding - diluted	1,165	1,117	1,159	1,014

Amount of dividends paid to participating securities (unvested awards) on a basis equivalent to holders of an entity's common stock plus an allocation of the undistributed earnings of an entity to the participating securities on the same basis as the paid dividends. This deduction in the EPS reconciliation is only applicable in periods when an entity generates income as the holders of the participating securities do not share in the losses of an entity unlike a common shareholder.

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This element represents the income or loss from continuing operations attributable to the parent which may also be defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests, if any.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

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Nonvested equity-based payment awards that contain forfeitable rights to dividends or dividend equivalents (whether paid or unpaid) that result in incremental common shares.

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