XML 1039 R78.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Inventories - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Inventory Disclosure [Abstract] |  |  |
Percentage inventories valued on a last in, first out (LIFO) basis | 34.00% | 35.00% |
Total inventories valued on an average-cost basis | $ 691 | $ 770 |
Recognition of income caused by partial liquidations of the lower cost LIFO inventory base, gross | 26 | 1 | 2
Recognition of income caused by partial liquidations of the lower cost LIFO inventory base, after tax | $ 17 | $ 1 | $ 1

X
- Definition Recognition of income caused by partial liquidations of the lower cost LIFO inventory base gross. + References No definition available. + Details
Name: | aa_RecognitionOfIncomeCausedByPartialLiquidationsOfLowerCostLifoInventoryBaseGross
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Recognition of income caused by partial liquidations of lower cost LIFO inventory base net. + References No definition available. + Details
Name: | aa_RecognitionOfIncomeCausedByPartialLiquidationsOfLowerCostLifoInventoryBaseNet
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition The percentage of LIFO (last in first out) inventory to total inventory as of the balance sheet date if other than 100 percent. + References No definition available. + Details
Name: | us-gaap_PercentageOfLIFOInventory
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount of weighted average cost inventory present at the reporting date when inventory is valued using different valuation methods. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766 + Details
Name: | us-gaap_WeightedAverageCostInventoryAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant