Debt E.ON Contingent Obligation (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Other Liabilities [Member] E.ON contingent obligation [Member]	Dec. 31, 2013 Other Liabilities [Member] E.ON contingent obligation [Member]
Debt Instrument [Line Items]
Unrealized gain on E.ON obligation	$ 1,059	$ 16,428
E.ON contingent obligation – principal			(12,902)	(12,902)
E.ON contingent obligation – accrued interest			(4,938)	(3,879)
E.ON contingent obligation – derivative asset			17,840	16,781
E.ON contingent obligation			$ 0	$ 0

This amount represents the derivative asset recorded for the E.ON contingent obligation, which is defined as the sum of the carrying values as of the balance sheet date of the E.ON Contingent Obligation which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer. The E.ON contingent obligation consists of the aggregate E.ON payments. Obligation to make repayments is contingent upon certain operating criteria. When the conditions for repayment are met, and for so long so those conditions continue to be met, there is obligation to make principal and interest payments.

No definition available.

Name:	cenx_E.ONContingentObligationDerivativeAsset
Namespace Prefix:	cenx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant