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Business acquisitions Sebree employees (Details) (Sebree Smelter [Member]) | Jun. 01, 2013
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Sebree Smelter [Member] |
Business Acquisition [Line Items] |
Employees | 500 dei_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