Income Taxes	6 Months Ended
Jun. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	K. Income Taxes – The effective tax rate for the second quarter of 2015 and 2014 was 26.6% (provision on income) and 37.7% (provision on income), respectively. The rate for the 2015 second quarter differs from the U.S. federal statutory rate of 35% primarily due to a $21 favorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (partial reversal of the 2015 first quarter impact). The rate for the 2014 second quarter differs from the U.S. federal statutory rate of 35% primarily due to the U.S. tax impact of deemed distributions from otherwise lower tax rate foreign jurisdictions and operational income of certain foreign subsidiaries taxed in lower rate jurisdictions, mostly offset by a $20 favorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (partial reversal of the 2014 first quarter impact). The effective tax rate for the 2015 and 2014 six-month periods was 39.4% (provision on income) and 1.5% (provision on a loss), respectively. The rate for the 2015 six-month period differs from the U.S. federal statutory rate of 35% primarily due to a $34 net discrete income tax charge as described below, a loss on the sale of a rolling mill in Russia (see Note E) for which no tax benefit was recognized, and a $14 unfavorable impact related to the interim period treatment of losses in certain foreign jurisdictions for which no tax benefit was recognized (impact is expected to reverse by the end of 2015), somewhat offset by foreign income taxed in lower rate jurisdictions. In the first quarter of 2015, AWAC, a joint venture owned 60% by Alcoa and 40% by Alumina Limited (Alcoa consolidates AWAC for financial reporting purposes), recognized an $83 discrete income tax charge (increased to $85 in the 2015 second quarter) for a valuation allowance on certain deferred tax assets, which were related mostly to employee benefits and tax loss carryforwards. Alcoa also had a $50 deferred tax liability (increased to $51 in the 2015 second quarter) related to its 60%-share of these deferred tax assets that was written off as a result of the valuation allowance recognized by AWAC. The rate for the 2014 six-month period differs (by (36.5) percentage points) from the U.S. federal statutory rate of 35% primarily due to a $36 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 2014).

K. Income Taxes – The effective tax rate for the second quarter of 2015 and 2014 was 26.6% (provision on income) and 37.7% (provision on income), respectively.

The rate for the 2015 second quarter differs from the U.S. federal statutory rate of 35% primarily due to a $21 favorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (partial reversal of the 2015 first quarter impact).

The rate for the 2014 second quarter differs from the U.S. federal statutory rate of 35% primarily due to the U.S. tax impact of deemed distributions from otherwise lower tax rate foreign jurisdictions and operational income of certain foreign subsidiaries taxed in lower rate jurisdictions, mostly offset by a $20 favorable impact related to the interim period treatment of operational losses in certain foreign jurisdictions for which no tax benefit was recognized (partial reversal of the 2014 first quarter impact).

The effective tax rate for the 2015 and 2014 six-month periods was 39.4% (provision on income) and 1.5% (provision on a loss), respectively.

The rate for the 2015 six-month period differs from the U.S. federal statutory rate of 35% primarily due to a $34 net discrete income tax charge as described below, a loss on the sale of a rolling mill in Russia (see Note E) for which no tax benefit was recognized, and a $14 unfavorable impact related to the interim period treatment of losses in certain foreign jurisdictions for which no tax benefit was recognized (impact is expected to reverse by the end of 2015), somewhat offset by foreign income taxed in lower rate jurisdictions.

In the first quarter of 2015, AWAC, a joint venture owned 60% by Alcoa and 40% by Alumina Limited (Alcoa consolidates AWAC for financial reporting purposes), recognized an $83 discrete income tax charge (increased to $85 in the 2015 second quarter) for a valuation allowance on certain deferred tax assets, which were related mostly to employee benefits and tax loss carryforwards. Alcoa also had a $50 deferred tax liability (increased to $51 in the 2015 second quarter) related to its 60%-share of these deferred tax assets that was written off as a result of the valuation allowance recognized by AWAC.

The rate for the 2014 six-month period differs (by (36.5) percentage points) from the U.S. federal statutory rate of 35% primarily due to a $36 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 2014).