XML 70 R27.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Pension And Other Postretirement Benefits (Tables) | 3 Months Ended
--- | ---
Mar. 31, 2012
Pension And Other Postretirement Benefits [Abstract] |
Schedule Of Components Of Net Periodic Benefit Cost |
|  | Pension benefits |  |  | Other postretirement benefits |
First quarter ended March 31, |  | 2012 |  |  | 2011 |  |  | 2012 |  |  | 2011 |
Service cost |  | $ | 47 |  |  | $ | 41 |  |  | $ | 4 |  |  | $ | 4 |
Interest cost |  |  | 160 |  |  |  | 169 |  |  |  | 33 |  |  |  | 40 |
Expected return on plan assets |  |  | (202 | ) |  |  | (201 | ) |  |  | — |  |  |  | (1 | )
Amortization of prior service cost (benefit) |  |  | 5 |  |  |  | 5 |  |  |  | (4 | ) |  |  | (4 | )
Recognized net actuarial loss |  |  | 96 |  |  |  | 62 |  |  |  | 6 |  |  |  | 7 |
Net periodic benefit cost |  | $ | 106 |  |  | $ | 76 |  |  | $ | 39 |  |  | $ | 46 |

X
- Definition Schedule Of Components of Net Periodic Benefit Cost [Text Block] + References No definition available. + Details
Name: | aa_ScheduleOfComponentsOfNetPeriodicBenefitCostTextBlock
Namespace Prefix: | aa_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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