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Contingencies and Commitments - Additional Information - 2 (Detail) | 3 Months Ended |  |  |  |  |  |  | 0 Months Ended | 1 Months Ended | 0 Months Ended |  | 0 Months Ended | 3 Months Ended | 1 Months Ended | 0 Months Ended | 36 Months Ended |  | 3 Months Ended | 12 Months Ended | 31 Months Ended | 12 Months Ended | 3 Months Ended |  |  | 3 Months Ended |  |  | 12 Months Ended | 3 Months Ended | 12 Months Ended | 1 Months Ended | 3 Months Ended
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Mar. 31, 2014 USD ($) Agency Entity | Mar. 31, 2014 EUR (€) | Dec. 31, 2013 USD ($) | Jun. 30, 2012 USD ($) | Jun. 30, 2012 EUR (€) | Mar. 31, 2014 Other Noncurrent Liabilities and Deferred Credits [Member] USD ($) | Dec. 31, 2013 Other Noncurrent Liabilities and Deferred Credits [Member] USD ($) | Mar. 31, 2014 State and Local Jurisdiction [Member] USD ($) | Mar. 31, 2014 State and Local Jurisdiction [Member] BRL | Apr. 08, 2013 Alcoa World Alumina Brasil [Member] BRL | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] USD ($) | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] BRL | May 31, 2012 Alcoa World Alumina Brasil [Member] USD ($) | May 31, 2012 Alcoa World Alumina Brasil [Member] BRL | Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Minimum [Member] USD ($) | Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Maximum [Member] USD ($) | Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] BRL | Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] Minimum [Member] USD ($) | Apr. 08, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] Maximum [Member] USD ($) | Feb. 27, 2014 Ligestra [Member] USD ($) | Feb. 27, 2014 Ligestra [Member] EUR (€) | Mar. 31, 2014 Ligestra [Member] | Jan. 31, 2014 Ligestra [Member] Minimum [Member] | Jan. 31, 2014 Ligestra [Member] Maximum [Member] | Feb. 27, 2014 Italian Ministry of Environment and Protection of Land and Sea[Member] USD ($) | Feb. 27, 2014 Italian Ministry of Environment and Protection of Land and Sea[Member] EUR (€) | Dec. 31, 2002 Alcoa Aluminio [Member] t | Mar. 31, 2014 Alcoa [Member] USD ($) | Mar. 31, 2014 Estreito Project [Member] USD ($) MWh | Mar. 31, 2014 Estreito Project [Member] BRL | Dec. 31, 2013 Estreito Project [Member] USD ($) | Dec. 31, 2013 Estreito Project [Member] BRL | Mar. 31, 2013 Estreito Project [Member] USD ($) MWh | Dec. 31, 2009 Fusina [Member] USD ($) | Dec. 31, 2012 Baie Comeau [Member] USD ($) | Dec. 31, 2012 Mosjoen [Member] USD ($) | Mar. 31, 2014 Ma'aden Joint Venture [Member] Entity | Mar. 31, 2014 Smelting and Rolling Mill Companies [Member] USD ($) | Mar. 31, 2014 Smelting and Rolling Mill Companies [Member] Other Noncurrent Liabilities and Deferred Credits [Member] USD ($) | Dec. 31, 2013 Smelting and Rolling Mill Companies [Member] Other Noncurrent Liabilities and Deferred Credits [Member] USD ($) | Mar. 31, 2014 Alcoa Joint Venture [Member] USD ($) | Mar. 31, 2014 Alcoa Joint Venture [Member] SAR | Dec. 31, 2013 Alcoa Joint Venture [Member] USD ($) | Dec. 31, 2009 Portovesme [Member] USD ($) | Mar. 31, 2014 Refining and Mining Company [Member] USD ($) | Mar. 31, 2014 Alumina Limited [Member] | Dec. 31, 2004 Dampier to Bunbury Natural Gas Pipeline [Member] USD ($) | Dec. 31, 2004 Dampier to Bunbury Natural Gas Pipeline [Member] AUD | Mar. 31, 2014 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] USD ($) | Mar. 31, 2014 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] AUD | Mar. 31, 2014 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] USD ($) | Mar. 31, 2014 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] AUD
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Remediation reserve increase (decrease) | $ 38,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 12,000,000 | $ 25,000,000 | $ 20,000,000 |  |  |  |  |  |  |  | $ 3,000,000 |  |  |  |  |  |  |  |
Percentage of payments and remediation costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% | 80.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Soil remediation project, estimated cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 33,000,000 | 24,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payment for emergency action and natural resource damages |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 25,000,000 | 18,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Costs and payments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 17,000,000 | 12,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Costs and payments related to damages |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9 | 6 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payment period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Disallowed tax credits |  |  |  |  |  |  |  |  |  |  | 110,000,000 | 220,000,000 |  |  |  |  | 175,000,000 | 0 | 80,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of penalty of the gross disallowed amount |  |  |  |  |  |  |  |  |  |  | 50.00% | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value added tax receivable |  |  |  |  |  |  |  |  |  |  |  |  | 41,000,000 | 82,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated range of reasonably possible loss, minimum |  |  |  |  |  |  |  |  |  | 155,000,000 |  |  |  |  | 0 | 70,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Administrative appeal, assessment period |  |  |  |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total combined assessments | 333,000,000 | 242,000,000 |  |  |  |  |  | 55,000,000 | 125,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Metal sold per month |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 25.49% | 25.49% |  |  | 25.49% |  |  |  |  |  |  |  |  |  |  |  |  |  | 20.00% | 20.00% |  |  |  |
Assured power from installed capacity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150 | 150 |  |  | 150 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated project costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,290,000,000 | 5,170,000,000 |  | 5,170,000,000 | 2,290,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aluminio's share of project |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 580,000,000 | 1,320,000,000 |  | 1,320,000,000 | 580,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commitment expended on the project |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 560,000,000 | 1,270,000,000 | 560,000,000 | 1,270,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest issued as guarantee for smelting and rolling mill companies |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 74.90% | 25.10% |  |  | 25.10% |  |  |  |  |  |  |  |  |  |  |
Number of joint venture entities | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capital investment | 1,949,000,000 |  | 1,907,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,515,000,000 |  |  | 10,800,000,000 | 40,500,000,000 |  |  | 1,992,000,000 |  |  |  |  |  |  |
Amount invested by Alcoa and Aluminum Financing Limited |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,100,000,000 |  |  |  |  |  |  |  |  |  |  |
Capital investment commitment paid-to-date |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 886,000,000 |  |  |  |  |  |  |  |  |  |  |
Capital investment commitment paid in period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 54,000,000 |  |  |  |  |  |  |  |  |  |  |
Equity method investment, carrying value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 967,000,000 |  | 951,000,000 |  |  |  |  |  |  |  |  |
Guarantee issued on behalf of smelting and rolling mill companies |  |  |  |  |  | 3,000,000 | 4,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,133,000,000 |  |  |  |  |  |  |  |  |  |  | 8,000,000 | 10,000,000 |  |  |  |  | 500,000,000 |  |  |  |  |  |  |
Debt service requirements, principal | 60,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 121,000,000 |  |  |  |  |  |  | 67,000,000 |  |  |  |  |  |  |
Debt service requirements, interest maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 60,000,000 |  |  |  |  |  |  | 30,000,000 |  |  |  |  |  |  |
Project financing | 240,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership interest in joint venture at fair market value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40.00% |  |  |  |  |  |
Number of agencies | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum percentage of equity investment | 67.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum percentage of equity Investment | 67.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Initial cash investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 17,000,000 | 24,000,000 |  |  |  |
Additional contributions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 141,000,000 | 176,000,000 | 31,000,000 | 31,000,000 | 2,000,000 | 2,000,000
Required plan contributions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40,000,000 | 40,000,000
Prepayments made under the agreement for future gas transmission services |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 327,000,000 | 355,000,000 | 327,000,000 | 355,000,000
Alcoa's maximum exposure to loss in projects |  |  |  | $ 417,000,000 | € 303,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 460,000,000 | 500,000,000 | $ 460,000,000 | 500,000,000

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