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Business Segments (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 12 Months Ended
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Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2010 | Sep. 30, 2010 | Jun. 30, 2010 | Mar. 31, 2010 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Business Segments [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of reportable business segment | 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |
Reconciliation of consolidated assets to total primary aluminum segment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment assets | $ 1,811,094 | [1] |  |  |  |  |  |  | $ 1,923,056 | [1] |  |  |  |  |  | $ 1,811,094 | [1] | $ 1,923,056 | [1] | $ 1,861,750 | [1]
Geographic information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net sales | 318,164 | [2] | 345,646 | [3] | 366,277 | [4] | 326,337 | [5] | 316,851 | [6] | 279,178 | [7] | 287,853 | [8] | 285,389 | 1,356,424 |  | 1,169,271 |  | 899,253 |
Number of major customers whose sales revenue exceeded ten percent of net sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  | 3 |  | 3 |
Percentage of sales to a single customer that will constitutes a major customer (in hundredths) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  | 10.00% |  | 10.00% |
Glencore [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Major customer information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales revenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 564,431 |  | 413,408 |  | 230,909 |
Southwire [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Major customer information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales revenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 373,505 |  | 323,873 |  | 234,535 |
BHP Billiton [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Major customer information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales revenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 239,157 |  | 214,571 |  | 166,546 |
United States [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Geographic information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 835,796 |  | 714,409 |  | 565,999 |
Long-lived assets | 401,173 | [9] |  |  |  |  |  |  | 412,266 | [9] |  |  |  |  |  | 401,173 | [9] | 412,266 | [9] | 436,798 | [9]
Iceland [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Geographic information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 520,628 |  | 453,021 |  | 332,927 |
Long-lived assets | 884,682 | [9] |  |  |  |  |  |  | 894,297 | [9] |  |  |  |  |  | 884,682 | [9] | 894,297 | [9] | 899,855 | [9]
Others [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Geographic information [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  | 1,841 |  | 327 |
Long-lived assets | 36,919 | [9] |  |  |  |  |  |  | 39,415 | [9] |  |  |  |  |  | 36,919 | [9] | 39,415 | [9] | 35,629 | [9]
Primary [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reconciliation of consolidated assets to total primary aluminum segment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment assets | 1,767,305 | [1] |  |  |  |  |  |  | 1,895,430 | [1] |  |  |  |  |  | 1,767,305 | [1] | 1,895,430 | [1] | 1,815,589 | [1]
Corporate Unallocated [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reconciliation of consolidated assets to total primary aluminum segment [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Segment assets | $ 43,789 | [1] |  |  |  |  |  |  | $ 27,626 | [1] |  |  |  |  |  | $ 43,789 | [1] | $ 27,626 | [1] | $ 46,161 | [1]
[1] | Segment assets include cash and cash equivalents, accounts receivable, due from affiliates, prepaid and other current assets, inventory, intangible assets and property, plant and equipment-net; the remaining assets are unallocated corporate assets.
[2] | The fourth quarter of 2011 net loss includes benefit of $3,067 for mark-to-market gains primarily related to primary aluminum price protection options and a $6,303 charge for lower of cost or market inventory adjustments.
[3] | The third quarter of 2011 net loss includes a benefit of $4,163 for mark-to-market gains primarily related to primary aluminum price protection options and a $13,479 charge for lower of cost or market inventory adjustments.
[4] | The second quarter of 2011 net income includes a benefit of $8,953 for changes to the Century of West Virginia retiree medical benefits program, a $7,707 charge related to the contractual impact of recent changes in the composition of our Board of Directors and executive management team and a $2,889 charge related to an insurance claim receivable.
[5] | The first quarter of 2011 net income includes a charge of $4,809 for mark-to-market losses primarily related to primary aluminum price protection options, a benefit of $9,418 for changes to the Century of West Virginia retiree medical benefits program and a $6,462 charge for the restart of the curtailed potline at Hawesville.
[6] | The fourth quarter of 2010 net income includes a benefit of $56,728 for changes to the Century of West Virginia retiree medical benefits program, a charge of $5,681 for mark-to-market losses for primary aluminum price protection options and a charge for contractual termination pension benefits of $4,555 due to the continued curtailment of the Ravenswood facility.
[7] | The third quarter of 2010 net loss includes a charge of $12,136 for mark-to-market losses primarily related to primary aluminum price protection options and a $7,300 benefit for lower of cost or market inventory adjustments.
[8] | The second quarter of 2010 net income includes a charge of $9,294 for mark-to-market losses primarily related to primary aluminum price protection options and a $7,056 charge for lower of cost or market inventory adjustments.
[9] | Includes long-lived assets other than financial instruments

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