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Summary of significant accounting policies Schedule of Property, Plant and Equipment (Details)	12 Months Ended
	Dec. 31, 2014
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life minimum (in years)	10cenx_EstimatedUsefulLifeMinimumInYears / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_BuildingAndBuildingImprovementsMember
Estimated useful life maximum (in years)	45cenx_EstimatedUsefulLifeMaximumInYears / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_BuildingAndBuildingImprovementsMember
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life minimum (in years)	5cenx_EstimatedUsefulLifeMinimumInYears / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_MachineryAndEquipmentMember
Estimated useful life maximum (in years)	35cenx_EstimatedUsefulLifeMaximumInYears / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_MachineryAndEquipmentMember

X

- Definition

The maximum useful life of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References

No definition available.

+ Details

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X

- Definition

The minimum useful life of long lived, physical assets used in the normal conduct of business and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References

No definition available.

+ Details

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X

- Details

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X

- Details

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X

- Details

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