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Curtailment of operations Ravenswood and Hawesville (Details) (USD $) In Thousands, unless otherwise specified | 1 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2009 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Curtailment of operations - Ravenswood and Hawesville [Abstract] |  |  |  |
Number of potlines curtailed | 1 |  |  |
Number of potlines at Hawesville | 5 |  |  |
Curtailment of potlines reduced aluminum production by approximately (in metric tons) | 49,000 |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total curtailment expense (benefit) |  | $ (3,806) | $ (37,386) | $ 41,710
Total cash curtailment cost |  | 22,966 | 17,429 | 46,700
Severance - Employee Related Cost [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total curtailment expense (benefit) |  | 1,038 | 455 | 22,049
Alumina Contract [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total curtailment expense (benefit) |  | 0 | 0 | 7,448
Power And Other Contract Termination Costs [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total curtailment expense (benefit) |  | 0 | 0 | 6,332
Ongoing Site Costs [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total curtailment expense (benefit) |  | 12,313 | 14,332 | 18,233
Pension Plan Curtailment Adjustment [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total curtailment expense (benefit) |  | 1,147 | 4,555 | 2,478
OPEB Plan Curtailment Adjustment [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total curtailment expense (benefit) |  | (18,304) | (56,728) | (14,830)
Curtailment At Ravenswood and Hawesville [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total cash curtailment cost |  | 13,502 | 10,078 | 22,300
Ravenswood Ongoing Idling Costs [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total cash curtailment cost |  | 9,464 | 7,351 | 9,300
Contract Termination and Amendment Costs [Member] |  |  |  |
Restructuring Costs [Abstract] |  |  |  |
Total cash curtailment cost |  | $ 0 | $ 0 | $ 15,100

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- Definition Reduction of electrolytic cells (potlines) reduced the production aluminum. + References No definition available. + Details
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- Definition The amount of cash paid during the reporting period for charges associated with the consolidation and relocation of operations, disposition or abandonment of operations or productive assets (that is, for reorganizing and restructuring charges and other related expenses). These charges may be incurred in connection with a business combination, change in strategic plan, a managerial response to declines in demand, increasing costs or other environmental factors. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -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 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 + Details
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- Definition Amount of costs incurred to date for the specified type of restructuring cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=6394695&loc=d3e140904-122747 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 146 -Paragraph 20 -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 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 95-3 -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 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section P -Subsection 3, 4 + Details
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