Income Taxes	9 Months Ended
Sep. 30, 2013
Income Tax Disclosure [Abstract]
Income Taxes	J. Income Taxes – The effective tax rate for the third quarter of 2013 and 2012 was 41.3% (provision on income) and 15.9% (benefit on a loss), respectively. The rate for the 2013 third quarter differs from the U.S. federal statutory rate of 35% primarily due to a $6 unfavorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (impact is expected to reverse by the end of 2013), partially offset by foreign income taxed in lower rate jurisdictions. The rate for the 2012 third quarter differs from the U.S. federal statutory rate of 35% primarily due to foreign income taxed in lower rate jurisdictions and a $35 unfavorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (impact reversed by the end of 2012), somewhat offset by a $12 benefit as a result of including the anticipated gain from the sale of the Tapoco Hydroelectric Project in the calculation of the estimated annual effective tax rate. The effective tax rate for the 2013 and 2012 nine-month periods was 63.7% (provision on income) and 25.1% (provision on a loss), respectively. The rate for the 2013 nine-month period differs from the U.S. federal statutory rate of 35% primarily due to a $103 nondeductible charge for a legal matter (see the Government Investigations section under Litigation in Note F), restructuring charges related to operations in Canada (benefit at a lower tax rate) and Italy (no tax benefit) (see Note C), and a $10 discrete income tax charge related to prior year taxes in Spain and Australia, somewhat offset by a $19 discrete income tax benefit related to new U.S. tax legislation. On January 2, 2013, the American Taxpayer Relief Act of 2012 was signed into law and reinstated various expired or expiring temporary business tax provisions through 2013. Two specific temporary business tax provisions that expired in 2011 and impacted Alcoa are the look-through rule for payments between related controlled foreign corporations and the research and experimentation credit. The expiration of these two provisions resulted in Alcoa recognizing a higher income tax provision of $19 in 2012. As tax law changes are accounted for in the period of enactment, Alcoa recognized the previously mentioned discrete income tax benefit in the 2013 first quarter related to the 2012 tax year to reflect the extension of these provisions. The rate for the 2012 nine-month period differs by (60.1)% points from the U.S. federal statutory rate of 35% primarily due to foreign income taxed in lower rate jurisdictions, a $39 unfavorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (impact reversed by the end of 2012), and an $8 discrete income tax charge related to prior year U.S. taxes on certain depletable assets, slightly offset by the previously mentioned $12 benefit.

J. Income Taxes – The effective tax rate for the third quarter of 2013 and 2012 was 41.3% (provision on income) and 15.9% (benefit on a loss), respectively.

The rate for the 2013 third quarter differs from the U.S. federal statutory rate of 35% primarily due to a $6 unfavorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (impact is expected to reverse by the end of 2013), partially offset by foreign income taxed in lower rate jurisdictions.

The rate for the 2012 third quarter differs from the U.S. federal statutory rate of 35% primarily due to foreign income taxed in lower rate jurisdictions and a $35 unfavorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (impact reversed by the end of 2012), somewhat offset by a $12 benefit as a result of including the anticipated gain from the sale of the Tapoco Hydroelectric Project in the calculation of the estimated annual effective tax rate.

The effective tax rate for the 2013 and 2012 nine-month periods was 63.7% (provision on income) and 25.1% (provision on a loss), respectively.

The rate for the 2013 nine-month period differs from the U.S. federal statutory rate of 35% primarily due to a $103 nondeductible charge for a legal matter (see the Government Investigations section under Litigation in Note F), restructuring charges related to operations in Canada (benefit at a lower tax rate) and Italy (no tax benefit) (see Note C), and a $10 discrete income tax charge related to prior year taxes in Spain and Australia, somewhat offset by a $19 discrete income tax benefit related to new U.S. tax legislation.

On January 2, 2013, the American Taxpayer Relief Act of 2012 was signed into law and reinstated various expired or expiring temporary business tax provisions through 2013. Two specific temporary business tax provisions that expired in 2011 and impacted Alcoa are the look-through rule for payments between related controlled foreign corporations and the research and experimentation credit. The expiration of these two provisions resulted in Alcoa recognizing a higher income tax provision of $19 in 2012. As tax law changes are accounted for in the period of enactment, Alcoa recognized the previously mentioned discrete income tax benefit in the 2013 first quarter related to the 2012 tax year to reflect the extension of these provisions.

The rate for the 2012 nine-month period differs by (60.1)% points from the U.S. federal statutory rate of 35% primarily due to foreign income taxed in lower rate jurisdictions, a $39 unfavorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (impact reversed by the end of 2012), and an $8 discrete income tax charge related to prior year U.S. taxes on certain depletable assets, slightly offset by the previously mentioned $12 benefit.