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Fair value measurements (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 31, 2012 Derivative Liabilities - Net [Member] | Mar. 31, 2011 Derivative Liabilities - Net [Member] | Mar. 31, 2012 Fair Value, Measurements, Recurring [Member] | Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] | Mar. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member] | Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member] | Mar. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member] | Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member] | Mar. 31, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member] | Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]
ASSETS: |  |  |  |  |  |  |  |  |  |
Cash equivalents |  |  | $ 175,321 | $ 176,284 | $ 175,321 | $ 176,284 | $ 0 | $ 0 | $ 0 | $ 0
Trust assets |  |  | 15,572 | 15,889 | 15,572 | 15,889 | 0 | 0 | 0 | 0
Surety bond – workers comp insurance |  |  | 2,391 | 2,391 | 2,391 | 2,391 | 0 | 0 | 0 | 0
Primary aluminum put option contracts |  |  | 2,981 | 9,331 | 0 | 0 | 2,981 | 9,331 | 0 | 0
Power contract |  |  | 53 | 106 | 0 | 0 | 0 | 0 | 53 | 106
TOTAL |  |  | 196,318 | 204,001 | 193,284 | 194,564 | 2,981 | 9,331 | 53 | 106
LIABILITIES: |  |  |  |  |  |  |  |  |  |
Natural gas forward financial purchase contracts |  |  | 236 | 281 | 0 | 0 | 236 | 281 | 0 | 0
E.ON contingent obligation – net |  |  | 14,310 | 13,958 | 0 | 0 | 0 | 0 | 14,310 | 13,958
Primary aluminum sales contract – premium collar |  |  | 1,169 | 908 | 0 | 0 | 0 | 0 | 1,169 | 908
TOTAL |  |  | 15,715 | 15,147 | 0 | 0 | 236 | 281 | 15,479 | 14,866
Level 3 fair value measurements [Roll Forward] |  |  |  |  |  |  |  |  |  |
Beginning balance | (14,760) | (13,802) |  |  |  |  |  |  |  |
Total loss (realized/unrealized) included in earnings | (613) | (473) |  |  |  |  |  |  |  |
Settlements | (53) | (36) |  |  |  |  |  |  |  |
Ending balance | (15,426) | (14,311) |  |  |  |  |  |  |  |
Amount of total loss included in earnings attributable to the change in unrealized losses (gains) relating to assets and liabilities held | $ 613 | $ 473 |  |  |  |  |  |  |  |

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- Definition Fair values as of the balance sheet date of all aluminum put option contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements. + References No definition available. + Details
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- Definition Fair values as of the balance sheet date of all primary aluminum sales contracts that meet the criteria of being accounted for as liability derivative instruments that do not qualify for normal purchases/normal sales exclusion. + References No definition available. + Details
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- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 8, 9, 10 -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 Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 -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 FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8 -Footnote 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. + Details
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