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Derivative and hedging instruments (Details) (Not Designated as Hedging Instrument [Member], USD $)
In Thousands, unless otherwise specified

Dec. 31, 2014

Dec. 31, 2013

Fair value of derivative assets and liabilities by balance sheet location [Abstract]

DERIVATIVE ASSETS

$ 0us-gaap_DerivativeAssets

$ 140us-gaap_DerivativeAssets

DERIVATIVE LIABILITIES

0us-gaap_DerivativeLiabilities

0us-gaap_DerivativeLiabilities

Midwest Premium Contracts [Member]

Outstanding forward contracts not designated as hedging instruments [Abstract]

Midwest premium contracts (tonnes)

0invest_DerivativeNonmonetaryNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_MidwestPremiumContractsMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

6,000invest_DerivativeNonmonetaryNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_MidwestPremiumContractsMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

Midwest Premium Contracts [Member] | Prepaid and Other Current Assets [Member]

Fair value of derivative assets and liabilities by balance sheet location [Abstract]

DERIVATIVE ASSETS

0us-gaap_DerivativeAssets
/ us-gaap_BalanceSheetLocationAxis
= cenx_PrepaidAndOtherCurrentAssetsMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_MidwestPremiumContractsMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

140us-gaap_DerivativeAssets
/ us-gaap_BalanceSheetLocationAxis
= cenx_PrepaidAndOtherCurrentAssetsMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_MidwestPremiumContractsMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

E.ON Contingent Obligation [Member] | Other Liabilities [Member]

Fair value of derivative assets and liabilities by balance sheet location [Abstract]

DERIVATIVE LIABILITIES

0us-gaap_DerivativeLiabilities
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_EOnContingentObligationMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

^[1]

0us-gaap_DerivativeLiabilities
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_EOnContingentObligationMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

^[1]

Primary Aluminum Sales Contracts [Member] | Accrued and Other Current Liabilities [Member]

Fair value of derivative assets and liabilities by balance sheet location [Abstract]

DERIVATIVE LIABILITIES

$ 0us-gaap_DerivativeLiabilities
/ us-gaap_BalanceSheetLocationAxis
= cenx_AccruedAndOtherLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_PrimaryAluminumSalesContractsMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

$ 140us-gaap_DerivativeLiabilities
/ us-gaap_BalanceSheetLocationAxis
= cenx_AccruedAndOtherLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_PrimaryAluminumSalesContractsMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

Primary Aluminum Sales Contract Premium [Member]

Outstanding forward contracts not designated as hedging instruments [Abstract]

Primary aluminum sales contract premium (tonnes) (1)

0cenx_AluminumForwardContractsOutstanding
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_PrimaryAluminumSalesContractPremiumMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

^[2]

1,782cenx_AluminumForwardContractsOutstanding
/ us-gaap_DerivativeInstrumentRiskAxis
= cenx_PrimaryAluminumSalesContractPremiumMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_NondesignatedMember

^[2]

[1]	See Note 6 Debt for additional information about the E.ON contingent obligation.
[2]	Represents the remaining physical deliveries under the Glencore Metal Agreement.

X

- Definition

The metric tons of aluminum covered by forward contracts outstanding for sales, put options and call options at the end of the period.

+ References

No definition available.

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X

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X

- Definition

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

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X

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13495-108611



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312



Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958



Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226008-175313

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- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13495-108611



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=34720828&loc=SL20225862-175312



Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958



Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=36459792&loc=SL20226008-175313

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- Details

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X

- Details

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