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Summary of significant accounting policies Schedule of Equity Method Investment, Equity method investee (Details) | Dec. 31, 2014
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Mt. Holly Partnership Aluminum Reduction Facility [Member] |
Schedule of Equity Method Investments [Line Items] |
Equity Method Investment, Ownership Percentage | 49.70%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cenx_PartnershipAluminumReductionFacilityMember
Mt. Holly Property, Plant and Equipment Owned By Partnership [Member] |
Schedule of Equity Method Investments [Line Items] |
Equity Method Investment, Ownership Percentage | 49.70%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cenx_PropertyPlantAndEquipmentOwnedByPartnershipMember
Baise Haohi Carbon Co Ltd [Member] |
Schedule of Equity Method Investments [Line Items] |
Equity Method Investment, Ownership Percentage | 40.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = cenx_BaiseHaohiCarbonCoLtdMember

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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
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- Details
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