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Derivative and hedging instruments Part 2 (Details) (Not Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
E.ON Contingent Obligation [Member] | Net Gain (Loss) on Forward and Derivative Contracts [Member]
Derivatives not designated as hedging instruments [Abstract]
Gain (loss) recognized in income from derivatives	$ 1,412us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_EOnContingentObligationMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = cenx_NetGainLossOnForwardContractsMember	$ 16,781us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_EOnContingentObligationMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = cenx_NetGainLossOnForwardContractsMember
E.ON Contingent Obligation [Member] | Interest Expense [Member]
Derivatives not designated as hedging instruments [Abstract]
Gain (loss) recognized in income from derivatives	(1,412)us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_EOnContingentObligationMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember	(1,412)us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_EOnContingentObligationMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = us-gaap_InterestExpenseMember
Midwest Premium Contracts [Member] | Net Gain (Loss) on Forward and Derivative Contracts [Member]
Derivatives not designated as hedging instruments [Abstract]
Gain (loss) recognized in income from derivatives	(1,080)us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_MidwestPremiumContractsMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = cenx_NetGainLossOnForwardContractsMember	140us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_MidwestPremiumContractsMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = cenx_NetGainLossOnForwardContractsMember
Primary Aluminum Sales Contracts [Member] | Net Gain (Loss) on Forward and Derivative Contracts [Member]
Derivatives not designated as hedging instruments [Abstract]
Gain (loss) recognized in income from derivatives	(153)us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_PrimaryAluminumSalesContractsMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = cenx_NetGainLossOnForwardContractsMember	(323)us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_PrimaryAluminumSalesContractsMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = cenx_NetGainLossOnForwardContractsMember
Primary Aluminum Sales Contracts [Member] | Related Party Sales [Member]
Derivatives not designated as hedging instruments [Abstract]
Gain (loss) recognized in income from derivatives	$ 292us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_PrimaryAluminumSalesContractsMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = cenx_RelatedPartySalesMember	$ 1,353us-gaap_DerivativeGainLossOnDerivativeNet / us-gaap_DerivativeInstrumentRiskAxis = cenx_PrimaryAluminumSalesContractsMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember / us-gaap_IncomeStatementLocationAxis = cenx_RelatedPartySalesMember

X

- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (a),(c),(d),(e)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNetAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration