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Fair value measurements (Tables) | 6 Months Ended
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Jun. 30, 2013
Fair Value Disclosures [Abstract] |
Schedule of valuation methodology used to measure assets and liabilities at fair value | The following section describes the valuation methodology used to measure our financial assets and liabilities that were accounted for at fair value and are categorized based on the fair value hierarchy described in Accounting Standards Codification Manual ("ASC") 820 "Fair Value Measurements."
Overview of Century’s valuation methodology
| Level | Significant inputs
Cash equivalents/money market funds | 1 | Quoted market prices
Trust assets (1) | 1 | Quoted market prices
Surety bonds | 1 | Quoted market prices
E.ON U.S. (“E.ON”) contingent obligation | 3 | Quoted LME forward market, management’s estimates of the LME forward market prices for periods beyond the quoted periods and management’s estimate of future level of operations at Century Aluminum of Kentucky, our wholly owned subsidiary (“CAKY”).
Primary aluminum sales premium contracts | 3 | Management’s estimates of future U.S. Midwest premium and risk-adjusted discount rates
(1) | Trust assets are currently invested in money market funds. These trust assets are held to fund the non-qualified supplemental executive pension benefit obligations for certain of our officers. The trust has sole authority to invest the funds in secure interest producing investments consisting of short-term securities issued or guaranteed by the United States government or cash and cash equivalents.
Financial assets and liabilities at fair value on a recurring basis |
Recurring Fair Value Measurements | As of June 30, 2013
| Level 1 | Level 2 | Level 3 | Total
ASSETS: |  |  |  |
Cash equivalents | $ | 105,104 |  | $ | — |  | $ | — |  | $ | 105,104 |
Trust assets (1) | 12,276 |  | — |  | — |  | 12,276 |
Surety bond – workers comp insurance | 1,574 |  | — |  | — |  | 1,574 |
TOTAL | $ | 118,954 |  | $ | — |  | $ | — |  | $ | 118,954 |
LIABILITIES: |  |  |  |
E.ON contingent obligation - net (2) | $ | — |  | $ | — |  | $ | — |  | $ | — |
Primary aluminum sales contract – premium collar | — |  | — |  | 773 |  | 773 |
TOTAL | $ | — |  | $ | — |  | $ | 773 |  | $ | 773 |
(1) | Trust assets are currently invested in money market funds and excludes the cash surrender value of the life insurance policies in the trust.
(2) | Based on the LME forward market prices for primary aluminum at June 30, 2013 and management's estimate of the LME forward market for periods beyond the quoted periods, we believe that we will not have any payment obligations for the E.ON contingent obligation through the term of the agreement which expires in 2028. See Note 10 Debt for additional information about the E.ON contingent obligation fair value.
Recurring Fair Value Measurements | As of December 31, 2012
| Level 1 | Level 2 | Level 3 | Total
ASSETS: |  |  |  |
Cash equivalents | $ | 168,309 |  | $ | — |  | $ | — |  | $ | 168,309 |
Trust assets (1) | 14,254 |  | — |  | — |  | 14,254 |
Surety bonds – workers comp insurance | 2,123 |  | — |  | — |  | 2,123 |
TOTAL | $ | 184,686 |  | $ | — |  | $ | — |  | $ | 184,686 |
LIABILITIES: |  |  |  |
E.ON contingent obligation- net | $ | — |  | $ | — |  | $ | 15,369 |  | $ | 15,369 |
Primary aluminum sales contract – premium collar | — |  | — |  | 1,170 |  | 1,170 |
TOTAL | $ | — |  | $ | — |  | $ | 16,539 |  | $ | 16,539 |
(1) | Trust assets are currently invested in money market funds and excludes the cash surrender value of the life insurance policies in the trust.
Change in level 3 fair value measurements |
Change in Level 3 Fair Value Measurements during the three months ended June 30,
| Derivative liabilities - net
| 2013 | 2012
Beginning balance, April 1, | $ | (1,030 | ) | $ | (15,426 | )
Total gain (loss) (realized/unrealized) included in earnings | 257 |  | (545 | )
Settlements | — |  | (53 | )
Ending balance, June 30, | $ | (773 | ) | $ | (16,024 | )
Amount of gain (loss) included in earnings attributable to the change in unrealized losses relating to assets and liabilities held at June 30, | $ | 257 |  | $ | (545 | )
Change in Level 3 Fair Value Measurements during the six months ended June 30,
| Derivative liabilities - net
| 2013 | 2012
Beginning balance, January 1, | $ | (16,539 | ) | $ | (14,760 | )
Total gain (loss) (realized/unrealized) included in earnings | 15,766 |  | (1,158 | )
Settlements | — |  | (106 | )
Ending balance, June 30, | $ | (773 | ) | $ | (16,024 | )
Amount of gain (loss) included in earnings attributable to the change in unrealized losses relating to assets and liabilities held at June 30, | $ | 15,766 |  | $ | (1,158 | )

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- Definition Schedule of Valuation Methodology for Assets and Liabilities at Fair Value [Table Text Block] + References No definition available. + Details
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- Definition Tabular disclosure of liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, by class that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). Where the quoted price in an active market for the identical liability is not available, the Level 1 input is the quoted price of an identical liability when traded as an asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 32 -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 820 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19190-110258 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 6 -Footnote 4 -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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- Definition Tabular disclosure of assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19190-110258 + Details
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