Commitments and Contingencies - Contingent obligation (Details) $ in Millions	12 Months Ended
Dec. 31, 2022 USD ($) paymentInstallment	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Contingent obligation	$ 0.0	$ 0.0
E.ON Contingent Obligation \| Other Liabilities
Debt Instrument [Line Items]
Contingent obligation – principal	(12.9)	(12.9)
Contingent obligation – accrued interest	(16.6)	(15.2)
Contingent obligation – derivative asset	$ 29.5	$ 28.1
Long-term Debt \| E.ON Contingent Obligation
Debt Instrument [Line Items]
Number of monthly installments \| paymentInstallment	72
Stated interest rate	10.94%
Realized gain (loss) on contingent obligation	$ 1.4

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