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Debt E.ON contingent obligation (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Debt Instrument [Line Items] |  |  |  |
Unrealized gain (loss) on E.ON obligation | $ 15,722 cenx_UnrealizedGainLossOnEOnObligation | $ 1,412 cenx_UnrealizedGainLossOnEOnObligation | $ 16,781 cenx_UnrealizedGainLossOnEOnObligation | $ 0 cenx_UnrealizedGainLossOnEOnObligation
E.ON Contingent Obligation |  | 0 cenx_EOnContingentObligation | 0 cenx_EOnContingentObligation |
Long-term Debt [Member] | Contingent obligation [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Payment terms |  | 72 monthly payments |  |
Unrealized gain (loss) on E.ON obligation |  | 1,412 cenx_UnrealizedGainLossOnEOnObligation / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember / us-gaap_LongtermDebtTypeAxis = us-gaap_LongTermDebtMember | 16,781 cenx_UnrealizedGainLossOnEOnObligation / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember / us-gaap_LongtermDebtTypeAxis = us-gaap_LongTermDebtMember |
Debt Instrument, Interest Rate, Stated Percentage |  | 10.94%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember / us-gaap_LongtermDebtTypeAxis = us-gaap_LongTermDebtMember |  |
Other Liabilities [Member] | Contingent obligation [Member] |  |  |  |
Debt Instrument [Line Items] |  |  |  |
E.ON contingent obligation – principal |  | (12,902)cenx_E.ONContingentObligationPrincipal / us-gaap_BalanceSheetLocationAxis = us-gaap_OtherLiabilitiesMember / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember | (12,902)cenx_E.ONContingentObligationPrincipal / us-gaap_BalanceSheetLocationAxis = us-gaap_OtherLiabilitiesMember / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember |
E.ON contingent obligation – accrued interest |  | (5,291)cenx_E.ONContingentObligationAccruedInterest / us-gaap_BalanceSheetLocationAxis = us-gaap_OtherLiabilitiesMember / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember | (3,879)cenx_E.ONContingentObligationAccruedInterest / us-gaap_BalanceSheetLocationAxis = us-gaap_OtherLiabilitiesMember / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember |
E.ON contingent obligation – derivative asset |  | 18,193 cenx_E.ONContingentObligationDerivativeAsset / us-gaap_BalanceSheetLocationAxis = us-gaap_OtherLiabilitiesMember / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember | 16,781 cenx_E.ONContingentObligationDerivativeAsset / us-gaap_BalanceSheetLocationAxis = us-gaap_OtherLiabilitiesMember / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember |
E.ON Contingent Obligation |  | $ 0 cenx_EOnContingentObligation / us-gaap_BalanceSheetLocationAxis = us-gaap_OtherLiabilitiesMember / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember | $ 0 cenx_EOnContingentObligation / us-gaap_BalanceSheetLocationAxis = us-gaap_OtherLiabilitiesMember / us-gaap_DebtInstrumentAxis = cenx_ContingentObligationMember |

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- Definition This amount represents the accrued interest on the E.ON contingent obligation, which is defined as the sum of the carrying values as of the balance sheet date of the E.ON Contingent Obligation which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer. The E.ON contingent obligation consists of the aggregate E.ON payments. Obligation to make repayments is contingent upon certain operating criteria. When the conditions for repayment are met, and for so long so those conditions continue to be met, there is obligation to make principal and interest payments. + References No definition available. + Details
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- Definition This amount represents the derivative asset recorded for the E.ON contingent obligation, which is defined as the sum of the carrying values as of the balance sheet date of the E.ON Contingent Obligation which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer. The E.ON contingent obligation consists of the aggregate E.ON payments. Obligation to make repayments is contingent upon certain operating criteria. When the conditions for repayment are met, and for so long so those conditions continue to be met, there is obligation to make principal and interest payments. + References No definition available. + Details
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- Definition This amount represents the principal amount of the E.ON contingent obligation, which is defined as the sum of the carrying values as of the balance sheet date of the E.ON Contingent Obligation which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer. The E.ON contingent obligation consists of the aggregate E.ON payments. Obligation to make repayments is contingent upon certain operating criteria. When the conditions for repayment are met, and for so long so those conditions continue to be met, there is obligation to make principal and interest payments. + References No definition available. + Details
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- Definition Sum of the carrying values as of the balance sheet date of the E.ON Contingent Obligation which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer. The E.ON contingent obligation consists of the aggregate E.ON payments. Obligation to make repayments is contingent upon certain operating criteria. When the conditions for repayment are met, and for so long so those conditions continue to be met, there is obligation to make principal and interest payments. + References No definition available. + Details
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- Definition The net change in the difference between the fair value and the carrying value on the contingent obligation held at each balance sheet date, that was included in earnings for the period. + References No definition available. + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Description of the payment terms of the debt instrument (for example, whether periodic payments include principal and frequency of payments) and discussion about any contingencies associated with the payment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(3)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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