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Segment And Geographic Area Information (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Minimum revenue percentage from aluminum and alumina | 80.00% |  |
Total export sales | $ 1,988 | $ 1,543 | $ 1,530
Aluminum [Member] |  |  |
Revenues from External Customers and Long-Lived Assets [Line Items] |  |  |
Sales percentage, maximum | 90.00% |  |

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- Definition Revenues from external customers attributed to all foreign countries in total from which the entity derives revenues. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 131 -Paragraph 38 -Subparagraph a(2) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599 + Details
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