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Segment Information (Schedule Of Operating Results And Assets Of Alcoa's Reportable Segments) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2012 | Mar. 31, 2011
Segment Reporting Information [Line Items] |  |  |  |
Third-party sales | $ 5,954 |  | $ 5,929 |
Intersegment sales | 1,422 |  | 1,541 |
Total sales | 7,376 |  | 7,470 |
Equity income (loss) | (2) |  | 5 |
Depreciation, depletion, and amortization | 346 |  | 340 |
Income taxes | 107 |  | 192 |
After-tax operating income (ATOI) | 296 |  | 555 |
Segment Information [Member] | Alumina [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Third-party sales | 775 |  | 810 |
Intersegment sales | 617 |  | 633 |
Total sales | 1,392 |  | 1,443 |
Equity income (loss) | 1 |  | 3 |
Depreciation, depletion, and amortization | 114 |  | 103 |
Income taxes | (1) |  | 44 |
After-tax operating income (ATOI) | 35 |  | 142 |
Segment Information [Member] | Primary Metals [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Third-party sales | 1,944 |  | 1,980 |
Intersegment sales | 761 |  | 839 |
Total sales | 2,705 |  | 2,819 |
Equity income (loss) | (2) |  | 1 |
Depreciation, depletion, and amortization | 135 |  | 141 |
Income taxes | (13) |  | 53 |
After-tax operating income (ATOI) | 10 |  | 202 |
Segment Information [Member] | Engineered Products And Solutions [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Third-party sales | 1,390 |  | 1,247 |
Intersegment sales |  |  |  |
Total sales | 1,390 |  | 1,247 |
Equity income (loss) |  |  | 1 |
Depreciation, depletion, and amortization | 40 |  | 38 |
Income taxes | 72 |  | 62 |
After-tax operating income (ATOI) | 155 |  | 130 |
Segment Information [Member] | Global Rolled Products [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Third-party sales | 1,845 | [1] | 1,892 | [1]
Intersegment sales | 44 | [1] | 69 | [1]
Total sales | 1,889 | [1] | 1,961 | [1]
Equity income (loss) | (1) | [1] |  | [1]
Depreciation, depletion, and amortization | 57 | [1] | 58 | [1]
Income taxes | 49 | [1] | 33 | [1]
After-tax operating income (ATOI) | $ 96 | [1] | $ 81 | [1]
[1] | In the first quarter of 2012, Alcoa changed the name of the Flat-Rolled Products segment to the Global Rolled Products segment

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