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Debt Industrial Revenue Bonds (Details) (Short-term Debt [Member], Industrial revenue bonds due 2028 [Member]) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013
Short-term Debt [Member] | Industrial revenue bonds due 2028 [Member] |  |
Short-term Debt [Line Items] |  |
Variable interest rates, maximum (as a percent) | 12.00%us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMaximum / us-gaap_DebtInstrumentAxis = cenx_IndustrialRevenueBondsDue2028Member / us-gaap_ShortTermDebtTypeAxis = us-gaap_ShortTermDebtMember | 12.00%us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMaximum / us-gaap_DebtInstrumentAxis = cenx_IndustrialRevenueBondsDue2028Member / us-gaap_ShortTermDebtTypeAxis = us-gaap_ShortTermDebtMember

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- Definition When presenting a range of interest rates, the highest effective rate for funds borrowed under the debt agreement as of the balance sheet date. + 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
Name: | us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMaximum
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_ShortTermDebtLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration