XML 64 R41.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Contingencies and Commitments - Additional Information - 1 (Detail) In Millions, unless otherwise specified | 1 Months Ended | 3 Months Ended | 6 Months Ended |  | 6 Months Ended | 1 Months Ended |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended |  | 3 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jan. 31, 2007 | Jun. 30, 2013 USD ($) | Jun. 30, 2013 USD ($) | Dec. 31, 2012 USD ($) | Dec. 31, 2012 EUR (€) | Jun. 30, 2013 Recurring Costs of Managing Hazardous Substances and Environmental Programs [Member] | Jan. 31, 2007 Spanish Government [Member] | Jan. 31, 2007 Tariffs Granted by Spain [Member] USD ($) | Jan. 31, 2007 Tariffs Granted by Spain [Member] EUR (€) | Jun. 30, 2003 Massena West, NY [Member] | Nov. 30, 2008 Grasse River [Member] USD ($) | Jun. 30, 2013 Grasse River [Member] USD ($) | Sep. 30, 2012 Grasse River [Member] USD ($) | Jun. 30, 2012 Grasse River [Member] USD ($) | Jun. 30, 2013 Grasse River [Member] USD ($) | Dec. 31, 2011 Grasse River [Member] USD ($) | Dec. 31, 2010 Grasse River [Member] USD ($) | Mar. 24, 2010 Grasse River [Member] USD ($) | Jun. 30, 2012 Smelter Sites [Member] USD ($) | Jun. 30, 2013 Massena West NY and Baie Comeau Quebec Canada [Member] USD ($)
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of years operating under a power supply structure |  |  |  |  |  |  | 9 years |  |  |  |  |  |  |  |  |  |  |  |  |
Days provided to submit observations and comments to the EC | 30 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss contingency, range of possible loss, maximum |  |  |  | $ 395 | € 303 |  |  | $ 90 | € 70 |  |  |  |  |  |  |  |  |  |  |
Number of cleanup locations |  |  | More than 100 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Remediation reserve balance |  | 535 | 535 | 532 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Remediation reserve balance, classified as a current liability |  | 69 | 69 | 74 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Remediation reserve increase |  |  |  |  |  |  |  |  |  |  | 40 | 17 | 128 | 37 | 16 | 1 | 2 |  | (30) |
Remediation reserve adjustment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 17 |  | 12
Increase and decrease in reserves due to effects of foreign currency translation |  | 6 | 11 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments related to remediation expenses applied against the reserve |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of cost of goods sold |  |  |  |  |  | 2.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of time between potential phenomenon occurrences, years |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |
Remediation alternative estimated cost |  |  | $ 243 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition Days provided to submit observations and comments. + References No definition available. + Details
Name: | aa_DaysProvidedToSubmitObservationsAndComments
Namespace Prefix: | aa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Environmental loss contingencies adjustment. + References No definition available. + Details
Name: | aa_EnvironmentalLossContingenciesAdjustment
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of cleanup locations. + References No definition available. + Details
Name: | aa_NumberOfCleanupLocations
Namespace Prefix: | aa_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Year operating under a power supply structured. + References No definition available. + Details
Name: | aa_NumberOfYearsOperatingUnderPowerSupplyStructured
Namespace Prefix: | aa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of cost of goods sold. + References No definition available. + Details
Name: | aa_PercentageOfCostOfGoodsSold
Namespace Prefix: | aa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period of time between potential phenomenon occurrences. + References No definition available. + Details
Name: | aa_PeriodOfTimeBetweenPotentialPhenomenonOccurrences
Namespace Prefix: | aa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingencies
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The aggregate amount disbursed during the reporting period to settle environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.Y.Q2) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingenciesPayments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Increase (decrease) in the accrual for environmental loss contingencies during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.Y.Q2) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingenciesPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable in twelve months or in the next operating cycle if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6911-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 10 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859 + Details
Name: | us-gaap_AccruedEnvironmentalLossContingenciesCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13296-110859 + Details
Name: | us-gaap_EnvironmentalRemediationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_LossContingenciesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The estimated maximum amount of possible loss from the contingency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyRangeOfPossibleLossMaximum
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Current period translation adjustment resulting from translating foreign currency financial statements into the reporting currency. Adjustment is not included in determining net income, but is reported in other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32022-110900 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32211-110900 + Details
Name: | us-gaap_TranslationAdjustmentFunctionalToReportingCurrencyIncreaseDecreaseGrossOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration