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Commitments and contingencies (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014 LaborUnions MW
OR Power Purchase Agreement Abstract]
Power currently available under the power purchase agreement (in megawatts)	47.5cenx_PowerAvailable
Power prepayments	$ 2,062us-gaap_PrepaidExpenseNoncurrent
Labor Commitments [Abstract]
Percentage of Company's work force represented by a union (in hundredths)	59.00%cenx_PercentageofWorkForceinUnion
Percentage of Grundartangi work force represented by the labor unions (in hundredths)	81.00%cenx_PercentageOfForeignWorkForceCoveredUnderNewLaborAgreement
Number of Labor Unions Under New Labor Agreement (in number of unions)	5cenx_NumberOfLaborUnionsUnderNewLaborAgreement
Percentage of Vlissingen work force represented by the labor union (in hundredths)	80.00%cenx_PercentageofforeignNetherlandsworkforcerepresentedbythelaborunioninhundredths
Percentage of U.S. based work force represented by a union (in hundredths)	54.00%cenx_PercentageOfDomesticWorkForceInUnion

X

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- Details

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Namespace Prefix:	cenx_
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X

- Definition

The number of labor unions representing a group of employees.

+ References

No definition available.

+ Details

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Namespace Prefix:	cenx_
Data Type:	xbrli:integerItemType
Balance Type:	na
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X

- Definition

The percentage of a Company's work force, based in the country of domicile, that are subject to collective bargaining agreements.

+ References

No definition available.

+ Details

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Namespace Prefix:	cenx_
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Balance Type:	na
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X

- Definition

The percentage of a Company's Netherlands work force that are subject to collective bargaining agreements

+ References

No definition available.

+ Details

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Namespace Prefix:	cenx_
Data Type:	num:percentItemType
Balance Type:	na
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X

- Definition

The percentage of a Company's Icelandic work force that are subject to collective bargaining agreements.

+ References

No definition available.

+ Details

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Namespace Prefix:	cenx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The percentage of a Company's work force that are subject to collective bargaining agreements.

+ References

No definition available.

+ Details

Name:	cenx_PercentageofWorkForceinUnion
Namespace Prefix:	cenx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The power currently available under the power purchase agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	cenx_
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Balance Type:	na
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X

- Definition

Sum of the carrying amounts as of the balance sheet date of amounts paid in advance for expenses which will be charged against earnings in periods after one year or beyond the operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682



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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

+ Details

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