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Contingencies and Commitments - Additional Information - 2 (Detail) In Millions, unless otherwise specified | 12 Months Ended |  |  | 12 Months Ended |  | 12 Months Ended |  | 1 Months Ended |  | 1 Months Ended |  | 12 Months Ended |  | 36 Months Ended | 12 Months Ended |  | 12 Months Ended | 9 Months Ended | 12 Months Ended |  | 12 Months Ended | 1 Months Ended | 12 Months Ended
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Dec. 31, 2013 USD ($) MW t | Dec. 31, 2012 USD ($) | Dec. 31, 2011 USD ($) | Dec. 31, 2013 EUR (€) | Jun. 12, 2012 USD ($) | Jun. 12, 2012 EUR (€) | Dec. 31, 2013 Minimum [Member] | Dec. 31, 2013 Maximum [Member] | Dec. 31, 2013 Energy, Raw Materials, and Other Goods and Services [Member] USD ($) | Dec. 31, 2013 Outstanding bank guarantees [Member] Minimum [Member] | Dec. 31, 2013 Outstanding bank guarantees [Member] Maximum [Member] | Dec. 31, 2013 State and Local Jurisdiction [Member] USD ($) | Dec. 31, 2013 State and Local Jurisdiction [Member] BRL | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] BRL | May 31, 2012 Alcoa World Alumina Brasil [Member] USD ($) | May 31, 2012 Alcoa World Alumina Brasil [Member] BRL | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] USD ($) | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] Minimum [Member] USD ($) | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] Maximum [Member] USD ($) | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] BRL | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] Minimum [Member] USD ($) | Mar. 31, 2013 Alcoa World Alumina Brasil [Member] Fixed Assets [Member] Maximum [Member] USD ($) | Dec. 31, 2013 Estreito Project [Member] USD ($) MWh | Dec. 31, 2013 Estreito Project [Member] BRL | Dec. 31, 2013 Barra Grande [Member] USD ($) MWh | Dec. 31, 2013 Barra Grande [Member] BRL MWh | Dec. 31, 2012 Barra Grande [Member] USD ($) | Dec. 31, 2012 Barra Grande [Member] BRL | Dec. 31, 2002 Alcoa Alumino [Member] t | Dec. 31, 2012 East St. Louis, IL Site [Member] USD ($) | Dec. 31, 2005 East St. Louis, IL Site [Member] USD ($) | Dec. 31, 2013 East St. Louis, IL Site [Member] USD ($) | Dec. 31, 2009 Fusina [Member] USD ($) | Dec. 31, 2009 Portovesme [Member] USD ($) | Dec. 31, 2013 Machadinho and Barra Grande [Member] | Dec. 31, 2013 Serrado Facao and Estreito Projects [Member] | Dec. 31, 2013 Machadinho [Member] MWh | Dec. 31, 2013 Serra Do Facao Project [Member] USD ($) | Dec. 31, 2013 Serra Do Facao Project [Member] BRL | Dec. 31, 2013 Serra Do Facao Project [Member] USD ($) MWh | Dec. 31, 2013 Serra Do Facao Project [Member] BRL MWh | Dec. 31, 2012 Serra Do Facao Project [Member] USD ($) | Dec. 31, 2012 Serra Do Facao Project [Member] BRL | Dec. 31, 2012 Baie Comeau [Member] USD ($) | Dec. 31, 2012 Mosjoen [Member] USD ($) | Dec. 31, 2004 Dampier to Bunbury Natural Gas Pipeline [Member] USD ($) | Dec. 31, 2004 Dampier to Bunbury Natural Gas Pipeline [Member] AUD | Dec. 31, 2013 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] USD ($) | Dec. 31, 2013 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] AUD | Dec. 31, 2013 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] USD ($) | Dec. 31, 2013 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] AUD | Dec. 31, 2012 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] USD ($) | Dec. 31, 2012 Dampier to Bunbury Natural Gas Pipeline [Member] Three-Year Equity Call Plan [Member] AUD
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Remediation reserve increase (decrease) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 14 | $ 15 |  | $ 12 | $ 3 |  |  |  |  |  |  |  |  |  | $ 25 | $ 20 |  |  |  |  |  |  |  |
Reserve balance | 509 | 532 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 26 |  | 24 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Disallowed tax credits |  |  |  |  |  |  |  |  |  |  |  |  |  | 220 |  |  | 110 |  |  | 175 | 0 | 75 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of penalty of the gross disallowed amount |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Value added tax receivable |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 41 | 82 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated range of reasonably possible loss, minimum |  |  |  |  |  |  |  |  |  |  |  |  |  | 155 |  |  |  | 0 | 65 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Administrative appeal, assessment period |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total combined assessments | 334 |  |  | 242 |  |  |  |  |  |  |  | 53 | 125 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Metal sold per month |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commitment to taking share of output in associated projects at cost, in years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30 years | 26 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investment percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 25.49% | 25.49% | 42.18% | 42.18% |  |  |  |  |  |  |  |  |  |  | 30.99% |  |  | 34.97% | 34.97% |  |  |  |  | 20.00% | 20.00% |  |  |  |  |  |
Assured power from installed capacity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150 | 150 | 160 | 160 |  |  |  |  |  |  |  |  |  |  | 120 |  |  | 65 | 65 |  |  |  |  |  |  |  |  |  |  |  |
Total investment in project |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 143 | 336 | 159 | 326 |  |  |  |  |  |  |  |  |  | 82 | 192 | 82 | 192 | 98 | 200 |  |  |  |  |  |  |  |  |  |
Estimated project costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,200 | 5,170 |  |  |  |  |  |  |  |  |  |  |  |  |  | 430 | 1,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aluminio's share of project |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 560 | 1,320 |  |  |  |  |  |  |  |  |  |  |  |  |  | 150 | 350 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional contributions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150 | 350 |  |  |  |  |  |  | 141 | 176 | 29 | 29 | 12 | 12 | 12 | 11
Increase in estimated costs to complete project |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 130 | 270 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commitment expended on the project |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 540 | 1,270 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of power self-sufficiency upon completion of project with full operating capacity | 70.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total energy demand | 690 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Temporarily declined in energy demand | 260 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Partial capacity curtailments of combined smelters | 128,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Initial cash investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 17 | 24 |  |  |  |  |  |
Required plan contributions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40 | 40 |  |
Prepayments made under the agreement for future gas transmission services |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 315 | 354 | 315 | 354 |  |
Alcoa's maximum exposure to loss in projects |  |  |  |  | 418 | 303 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 440 | 500 | 440 | 500 |  |
Purchase obligations due in 2014 | 159 |  |  |  |  |  |  |  | 3,319 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase obligations due in 2015 | 157 |  |  |  |  |  |  |  | 1,802 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase obligations due in 2016 | 145 |  |  |  |  |  |  |  | 1,628 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase obligations due in 2017 | 150 |  |  |  |  |  |  |  | 1,552 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase obligations due in 2018 | 149 |  |  |  |  |  |  |  | 1,838 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase obligations due thereafter | 2,091 |  |  |  |  |  |  |  | 9,856 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase obligations expenditures | 163 | 161 | 227 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expiration date of unconditional purchase obligations for energy |  |  |  |  |  |  | 2015 | 2036 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating leases, expense | 232 | 244 | 255 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term operating leases, minimum annual rentals due in 2014 | 198 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term operating leases, minimum annual rentals due in 2015 | 165 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term operating leases, minimum annual rentals due in 2016 | 135 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term operating leases, minimum annual rentals due in 2017 | 103 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term operating leases, minimum annual rentals due in 2018 | 80 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term operating leases, minimum annual rentals due thereafter | 244 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Guarantees of third party related to project financing | 542 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Guarantees, expiration date | 2019 |  |  |  |  |  |  |  |  | 2014 | 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Guarantees, total amount committed | 370 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letters of credit, total amount committed | 333 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letters of credit, expiration date | 2014 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total amount committed under outstanding surety bonds | $ 170 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Surety bonds, expiration date | 2014 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition Partial capacity curtailments of combined smelters. + References No definition available. + Details
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