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Forward delivery contracts and financial instruments (Details)	3 Months Ended
	Mar. 31, 2015 t		Dec. 31, 2014 t
Primary Aluminum Sales Contracts [Member] | Glencore Nordural Metal Agreement [Member]
Supply Commitment [Line Items]
Customer	Glencore	[1]
Volume	All primary aluminum produced at Grundartangi, net of tolling and other sales commitments	[1]
Volume (in tpy)	205,000cenx_AnnualPrimaryAluminumPhysicalDeliveryContract_Maximum / cenx_NameOfContractAxis = cenx_GlencoreNorduralMetalAgreementMember / us-gaap_SupplyCommitmentAxis = cenx_PrimaryAluminumSalesContractsMember
Term	January 1, 2014 through December 31, 2017	[1]
Pricing	Variable, based on LME and European Duty Paid premium	[1]
Primary Aluminum Sales Contracts [Member] | Glencore U.S. Aluminum Sales Agreement [Member]
Supply Commitment [Line Items]
Customer	Glencore
Volume	All primary aluminum produced in North America
Term	January 1, 2015 through December 31, 2016
Pricing	Variable, based on LME and Midwest premium and product premiums, as applicable
Long-Term Tolling Conctracts [Member] | Glencore Toll Agreement 1 [Member]
Supply Commitment [Line Items]
Customer	Glencore
Volume	90,000 tonnes per year ("tpy")
Volume (in tpy)	90,000cenx_AnnualPrimaryAluminumPhysicalDeliveryContract_Maximum / cenx_NameOfContractAxis = cenx_GlencoreTollAgreement1Member / us-gaap_SupplyCommitmentAxis = cenx_LongTermTollingContractsMember
Term	Through July 2016
Pricing	Variable, based on LME and European Duty Paid premium
Other Forward Delivery Contracts [Member]
Supply Commitment [Line Items]
Other forward delivery contracts to sell primary aluminum (in tonnes)	221cenx_OtherPrimaryAluminumDeliveryCommitmentsAndContractsVolume / us-gaap_SupplyCommitmentAxis = us-gaap_ForwardContractsMember		6,108cenx_OtherPrimaryAluminumDeliveryCommitmentsAndContractsVolume / us-gaap_SupplyCommitmentAxis = us-gaap_ForwardContractsMember
Glencore [Member] | Other Forward Delivery Contracts [Member]
Supply Commitment [Line Items]
Other forward delivery contracts to sell primary aluminum (in tonnes)	0cenx_OtherPrimaryAluminumDeliveryCommitmentsAndContractsVolume / us-gaap_MajorCustomersAxis = cenx_GlencoreMember / us-gaap_SupplyCommitmentAxis = us-gaap_ForwardContractsMember		4,058cenx_OtherPrimaryAluminumDeliveryCommitmentsAndContractsVolume / us-gaap_MajorCustomersAxis = cenx_GlencoreMember / us-gaap_SupplyCommitmentAxis = us-gaap_ForwardContractsMember
[1] The Glencore Grundartangi Metal Agreement is for all metal produced at Grundartangi from 2014 through 2017 less commitments under existing tolling and other sales contracts. Grundartangi currently estimates that it will sell Glencore approximately 205,000 tonnes of aluminum under this agreement in 2015.

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- Definition

Annual Primary Aluminum Physical Delivery Contract (Maximum)

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No definition available.

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- Definition

Long Term Contract For Purchase Of Primary Aluminum, Contract Expiration Date

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No definition available.

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- Definition

The description of the pricing terms for long term sales contracts.

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No definition available.

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- Definition

The name of a particular customer for a company.

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- Definition

Total amount of primary aluminum committed to be supplied under existing contracts or agreements outside of major long-term supply commitments.

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No definition available.

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- Definition

Description of the particular sales volume for a particular customer.

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No definition available.

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