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Quarterly Information (Unaudited) 2013 Financial Results Overview (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended							12 Months Ended
	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Abstract]
Sebree power contract amortization			$ 5,534cenx_AmortizationofAssumedPowerContract	$ 16,570cenx_AmortizationofAssumedPowerContract	$ 11,720cenx_AmortizationofAssumedPowerContract	$ 2,741cenx_AmortizationofAssumedPowerContract		$ 5,534cenx_AmortizationofAssumedPowerContract	$ 31,031cenx_AmortizationofAssumedPowerContract	$ 0cenx_AmortizationofAssumedPowerContract
Lower of cost or market inventory adjustments				9,040us-gaap_InventoryAdjustments	5,762us-gaap_InventoryAdjustments	10,211us-gaap_InventoryAdjustments	5,838us-gaap_InventoryAdjustments		9,040us-gaap_InventoryAdjustments
Litigation settlement expense	2,616us-gaap_LitigationSettlementExpense	500us-gaap_LitigationSettlementExpense		8,400us-gaap_LitigationSettlementExpense
Loss on early extinguishment of debt						3,272us-gaap_GainsLossesOnExtinguishmentOfDebt		0us-gaap_GainsLossesOnExtinguishmentOfDebt	(3,272)us-gaap_GainsLossesOnExtinguishmentOfDebt	0us-gaap_GainsLossesOnExtinguishmentOfDebt
Relocation expense						1,750cenx_Relocationexpense	2,213cenx_Relocationexpense
Increase (Decrease) in litigation reserve			3,100us-gaap_IncreaseDecreaseInLossAndLossAdjustmentExpenseReserve				2,225us-gaap_IncreaseDecreaseInLossAndLossAdjustmentExpenseReserve
Unrealized gain (loss) on E.ON obligation							15,722cenx_UnrealizedGainLossOnEOnObligation	1,412cenx_UnrealizedGainLossOnEOnObligation	16,781cenx_UnrealizedGainLossOnEOnObligation	0cenx_UnrealizedGainLossOnEOnObligation
Gain on bargain purchase						$ 5,253us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount		$ 0us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount	$ 5,253us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount	$ 0us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount

X

- Definition

The aggregate benefit recognized in earnings to allocate the assumed power contract liability in a systematic and rational manner over the contract period. As a noncash benefit, this element is subtracted from net income when calculating cash provided by or used in operations using the indirect method.

+ References

No definition available.

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X

- Definition

Severance and other expenses of related to the relocation of corporate headquarters

+ References

No definition available.

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X

- Definition

The net change in the difference between the fair value and the carrying value on the contingent obligation held at each balance sheet date, that was included in earnings for the period.

+ References

No definition available.

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- Definition

In a business combination in which the amount of net identifiable assets acquired and liabilities assumed exceeds the aggregate consideration transferred or to be transferred (as defined), this element represents the amount of gain recognized by the entity.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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The increase (decrease) during the reporting period in the reserve account established to account for expected but unspecified losses.

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Certain changes made in the current period to the value and amount of inventory reported.

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Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

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