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Business acquisitions Acquisition of Sebree aluminum smelter (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified | 3 Months Ended | 12 Months Ended | 3 Months Ended | 19 Months Ended |
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Dec. 31, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Jun. 30, 2014 | Dec. 31, 2014 | Jun. 01, 2013 t
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Purchase price cash paid |  |  |  |  |  | $ 1,042 us-gaap_PaymentsToAcquireBusinessesGross | $ 48,058 us-gaap_PaymentsToAcquireBusinessesGross |  | $ 0 us-gaap_PaymentsToAcquireBusinessesGross |  |  |
Gain on fair value of contingent consideration | 7,943 us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsRevenuesAndGainsRecognized |  |  |  |  | 7,943 us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsRevenuesAndGainsRecognized | 0 us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsRevenuesAndGainsRecognized |  | 0 us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsRevenuesAndGainsRecognized |  |  |
Gain on bargain purchase |  |  |  |  | 5,253 us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount | 0 us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount | 5,253 us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount |  | 0 us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount |  |  |
Sebree power contract amortization |  | 5,534 cenx_AmortizationofAssumedPowerContract | 16,570 cenx_AmortizationofAssumedPowerContract | 11,720 cenx_AmortizationofAssumedPowerContract | 2,741 cenx_AmortizationofAssumedPowerContract | 5,534 cenx_AmortizationofAssumedPowerContract | 31,031 cenx_AmortizationofAssumedPowerContract |  | 0 cenx_AmortizationofAssumedPowerContract |  |  |
Sebree Smelter [Member] |  |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Primary aluminum capacity (in tonnes) |  |  |  |  |  |  |  |  |  |  |  | 205,000 cenx_Primaryaluminumcapacity / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember
Purchase price |  |  |  |  |  |  |  |  |  |  |  | 61,000 cenx_BusinessAcquisitionPurchasePrice / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember
Purchase price cash paid |  |  |  |  |  |  |  |  |  |  | 49,035 us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Gain on fair value of contingent consideration |  |  |  |  |  |  |  |  |  | 965 us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsRevenuesAndGainsRecognized / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |
Gain on bargain purchase |  |  |  |  |  |  |  |  |  |  | 5,253 us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Cash |  |  |  |  |  |  |  |  |  |  | 48,083 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Deferred purchase price |  |  |  |  |  |  |  |  |  |  | 1,910 cenx_BusinessCombinationDeferredPurchasePrice / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Inventories | 59,018 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 59,018 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 59,018 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Prepaid and other current assets | 2,273 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 2,273 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 2,273 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Property, plant and equipment – net | 55,520 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 55,520 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 55,520 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Total assets acquired | 116,811 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 116,811 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 116,811 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Accrued and other current liabilities | 43,316 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 43,316 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 43,316 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Accrued pension benefit costs | 996 cenx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPensionBenefitCosts / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 996 cenx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPensionBenefitCosts / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 996 cenx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPensionBenefitCosts / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Accrued postretirement benefit costs | 6,544 cenx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPostRetirementBenefits / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 6,544 cenx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPostRetirementBenefits / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 6,544 cenx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedPostRetirementBenefits / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Other liabilities | 7,476 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 7,476 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 7,476 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Deferred taxes | 3,233 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilitiesNoncurrent / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 3,233 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilitiesNoncurrent / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 3,233 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilitiesNoncurrent / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Total liabilities assumed | 61,565 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 61,565 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  | 61,565 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |
Sebree revenue |  |  |  |  |  |  | 247,178 us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  |
Sebree income from continuing operations (1) |  |  |  |  |  |  | 8,705 us-gaap_BusinessCombinationProFormaInformationEarningsOrLossOfAcquireeSinceAcquisitionDateActual / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember | [1] |  |  |  |
Sebree power contract amortization |  |  |  |  |  | 5,534 cenx_AmortizationofAssumedPowerContract / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember | 31,031 cenx_AmortizationofAssumedPowerContract / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |  |  |
Pro forma revenues |  |  |  |  |  |  | 1,662,707 us-gaap_BusinessAcquisitionsProFormaRevenue / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  | 1,755,196 us-gaap_BusinessAcquisitionsProFormaRevenue / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |
Pro forma loss from continuing operations |  |  |  |  |  |  | $ (83,035)us-gaap_BusinessAcquisitionsProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTax / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  | $ (260,505)us-gaap_BusinessAcquisitionsProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTax / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |
Pro forma loss per common share, basic |  |  |  |  |  |  | $ (0.94)us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareBasic / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  | $ (2.94)us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareBasic / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |
Pro forma loss per common share, diluted |  |  |  |  |  |  | $ (0.94)us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareDiluted / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  | $ (2.94)us-gaap_BusinessAcquisitionProFormaIncomeLossFromContinuingOperationsBeforeChangesInAccountingAndExtraordinaryItemsNetOfTaxPerShareDiluted / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember |  |  |
[1] | Our net income for the years ended December 31, 2014 and 2013, includes a non-recurring credit for the amortization of the deferred power contract liability of $5,534 and $31,031, respectively, related to the amortization of an unfavorable power contract assumed as part of the Sebree acquisition resulting in a credit to our depreciation and amortization expense within cost of goods sold on the consolidated statement of operations for the first quarter of 2014. The power contract terminated on January 31, 2014.

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- Definition The aggregate benefit recognized in earnings to allocate the assumed power contract liability in a systematic and rational manner over the contract period. As a noncash benefit, this element is subtracted from net income when calculating cash provided by or used in operations using the indirect method. + References No definition available. + Details
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- Definition The amount of property, plant, and equipment recognized as of the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 55 -Paragraph 37 -URI http://asc.fasb.org/extlink&oid=35744172&loc=d3e2207-128464 + Details
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- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 + Details
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