Name:	cenx_LaborCommitmentsAbstract
Namespace Prefix:	cenx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Legal Contingencies [Abstract]

No definition available.

Name:	cenx_LegalContingenciesAbstract
Namespace Prefix:	cenx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Litigation Settlement, Amount Awarded to Other Party, Annual Payments

No definition available.

Name:	cenx_LitigationSettlementAmountAwardedtoOtherPartyAnnualPayments
Namespace Prefix:	cenx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Litigation Settlement Payment Period

No definition available.

Name:	cenx_LitigationSettlementPeriod
Namespace Prefix:	cenx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The number of labor unions representing a group of employees.

No definition available.

Name:	cenx_NumberOfLaborUnionsUnderNewLaborAgreement
Namespace Prefix:	cenx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

PBGC Settlement [Abstract]

No definition available.

Name:	cenx_PBGCSettlementAbstract
Namespace Prefix:	cenx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Pursuant to the terms of the settlement agreement with the Pension Benefit Guaranty Corporation, we will make additional contributions (above any minimum required contributions) to our defined benefit pension plans.

No definition available.

Name:	cenx_PensionContributionsAboveRequiredMinimumTotal
Namespace Prefix:	cenx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Pension Contributions, Amended Term, Annual Contribution

No definition available.

Name:	cenx_PensionContributionsAmendedTermAnnualContribution
Namespace Prefix:	cenx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Pension Contributions, Amended Term, Total Contribution

No definition available.

Name:	cenx_PensionContributionsAmendedTermTotalContribution
Namespace Prefix:	cenx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Pension Contributions, Term

No definition available.

Name:	cenx_PensionContributionsTerm
Namespace Prefix:	cenx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

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

No definition available.

Name:	cenx_PercentageOfDomesticWorkForceInUnion
Namespace Prefix:	cenx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Percentage Of Foreign Netherlands Work Force Represented By The Labor Union

No definition available.

Name:	cenx_PercentageOfForeignNetherlandsWorkForceRepresentedByTheLaborUnion
Namespace Prefix:	cenx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

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

No definition available.

Name:	cenx_PercentageOfForeignWorkForceCoveredUnderNewLaborAgreement
Namespace Prefix:	cenx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

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

No definition available.

Name:	cenx_PercentageofWorkForceinUnion
Namespace Prefix:	cenx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Power Supply Agreement, Increase Production At Full Capacity, Percentage

No definition available.

Name:	cenx_PowerSupplyAgreementIncreaseProductionAtFullCapacityPercentage
Namespace Prefix:	cenx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Ravenswood litigation [Abstract]

No definition available.

Name:	cenx_RavenswoodlitigationAbstract
Namespace Prefix:	cenx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Short-term Power Agreement, Supply Percentage

No definition available.

Name:	cenx_ShortTermPowerAgreementSupplyPercentage
Namespace Prefix:	cenx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The power currently available under the power purchase agreement.

No definition available.

Name:	cenx_UnderlyingDerivativePowerAvailable
Namespace Prefix:	cenx_
Data Type:	dtr-types:powerItemType
Balance Type:	na
Period Type:	instant

Underlying, Derivative Power, Available, Extension

No definition available.

Name:	cenx_UnderlyingDerivativePowerAvailableExtension
Namespace Prefix:	cenx_
Data Type:	dtr-types:powerItemType
Balance Type:	na
Period Type:	instant

Underlying, Derivative Power, Available, Requested

No definition available.

Name:	cenx_UnderlyingDerivativePowerAvailableRequested
Namespace Prefix:	cenx_
Data Type:	dtr-types:powerItemType
Balance Type:	na
Period Type:	instant

Underlying, Derivative Power, Rate

No definition available.

Name:	cenx_UnderlyingDerivativePowerRate
Namespace Prefix:	cenx_
Data Type:	dtr-types:powerItemType
Balance Type:	na
Period Type:	instant

Amount of gain (loss) recognized in settlement of litigation and insurance claims. Excludes claims within an insurance entity's normal claims settlement process.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349

Name:	us-gaap_GainLossRelatedToLitigationSettlement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount awarded to other party in judgment or settlement of litigation.

No definition available.

Name:	us-gaap_LitigationSettlementAmountAwardedToOtherParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of loss contingency liability.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=121557415&loc=d3e14615-108349

Name:	us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of loss contingency liability expected to be resolved within one year or the normal operating cycle, if longer.

Name:	us-gaap_LossContingencyAccrualCarryingValueCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of loss contingency liability expected to be resolved after one year or beyond the normal operating cycle, if longer.

Name:	us-gaap_LossContingencyAccrualCarryingValueNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of cash paid for the settlement of litigation or for other legal issues during the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3536-108585

Name:	us-gaap_PaymentsForLegalSettlements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of cash outflow for pension benefit. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree. Excludes other postretirement benefit.

Name:	us-gaap_PensionContributions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Name:	srt_CounterpartyNameAxis=cenx_PensionBenefitGuaranteeCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CounterpartyNameAxis=cenx_SanteeCooperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CounterpartyNameAxis=cenx_GrundartangiHSLandsvirkjunandORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CounterpartyNameAxis=cenx_GrundartangiLandsvirkjunMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_StatementGeographicalAxis=country_NL
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: