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Business acquisitions Acquisition of Mt. Holly smellter narrative other units (Details) (Mt. Holly Smelter [Member])	Dec. 01, 2014 t
Mt. Holly Smelter [Member]
Business Acquisition [Line Items]
Remaining percentage acquired in step acquisition	50.30%us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeIncludingSubsequentAcquisitionPercentage / us-gaap_BusinessAcquisitionAxis = cenx_Mt.HollySmelterMember
Percentage of ownership after step acquisition	100.00%cenx_BusinessAcquisitionPercentageofOwnershipAfterAcquisition / us-gaap_BusinessAcquisitionAxis = cenx_Mt.HollySmelterMember
Employees	600dei_EntityNumberOfEmployees / us-gaap_BusinessAcquisitionAxis = cenx_Mt.HollySmelterMember
Mt Holly primary aluminum capacity (tonnes)	231,000cenx_Primaryaluminumcapacity / us-gaap_BusinessAcquisitionAxis = cenx_Mt.HollySmelterMember
Equity interest percentage, pre step acquisition	49.70%us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage / us-gaap_BusinessAcquisitionAxis = cenx_Mt.HollySmelterMember

X

- Definition

Percentage of ownership at the acquisition date as a result of the business combination.

+ References

No definition available.

+ Details

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X

- Definition

Annual production capacity of primary aluminum (in tonnes).

+ References

No definition available.

+ Details

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Namespace Prefix:	cenx_
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X

- Definition

Number of persons employed by the Entity

+ References

No definition available.

+ Details

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Namespace Prefix:	dei_
Data Type:	xbrli:decimalItemType
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X

- Details

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X

- Definition

Percentage of voting equity interests acquired in a business combination achieved in stages, including equity interests in the acquiree held by the acquirer immediately before the acquisition date and acquired at the acquisition date.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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X

- Definition

Percentage of equity in the acquiree held by the acquirer immediately before the acquisition date in a business combination.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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