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Business acquisitions Sebree employees (Details) (Sebree Smelter [Member])	Jun. 01, 2013
Sebree Smelter [Member]
Business Acquisition [Line Items]
Employees	500dei_EntityNumberOfEmployees / us-gaap_BusinessAcquisitionAxis = cenx_SebreeSmelterMember

X

- Definition

Number of persons employed by the Entity

+ References

No definition available.

+ Details

Name:	dei_EntityNumberOfEmployees
Namespace Prefix:	dei_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

X

- Details

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