Debt Instrument, Principal Payment

No definition available.

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

- Definition

Carrying value as of the balance sheet date of the long-term debt associated with industrial revenue bonds. For classified balance sheets, these bonds are considered current assets because they are remarketed weekly and the bonds could be required to be repaid upon demand if there is a failed remarketing.

+ References

No definition available.

+ Details

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

- Definition

Interest Payable Outstanding

+ References

No definition available.

+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

+ Details

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

- Definition

Amount of interest payable on debt, including, but not limited to, trade payables.

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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount for notes payable (written promise to pay), due to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Balance Type:	credit
Period Type:	instant

- Definition

The amount for notes payable (written promise to pay), payable to related parties, which are due after one year (or one business cycle).

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Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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+ Details

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

- Definition

Carrying value as of the balance sheet date of the portion of long-term, collateralized debt obligations due within one year or the operating cycle, if longer. Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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+ Details

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

- Definition

Carrying amount of collateralized debt obligations with maturities initially due after one year or beyond the operating cycle, if longer, excluding the current portion. Obligations include, but not limited to, mortgage loans, chattel loans, and other borrowings secured by assets.

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cenx_SeniorsecurednotesdueJune012021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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- Details

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Debt (Details) - USD ($)	3 Months Ended
Debt (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019	Jun. 04, 2013
Debt Instrument [Line Items]
Hawesville term loan - current portion	$ 20,000,000.0	$ 20,000,000.0
Hancock County industrial revenue bonds (IRBs) due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%))	7,800,000	7,800,000
Hawesville term loan - less current portion, interest payable monthly	15,000,000.0	20,000,000.0
Total debt	382,100,000	301,000,000.0
Hawesville [Member]
Debt Instrument [Line Items]
Hawesville term loan - current portion	20,000,000.0	20,000,000.0
Hawesville term loan - less current portion, interest payable monthly	15,000,000.0	20,000,000.0
Long-term Debt [Member] \| Senior secured notes due June 01, 2021 [Member]
Debt Instrument [Line Items]
7.5% senior secured notes due June 2021, net of debt discount of $0.7 million and $0.8 million, respectively, interest payable semiannually	$ 249,300,000	249,200,000
Maturity date	Jun. 01, 2021
Stated interest rate, percentage	7.50%		7.50%
Debt discount	$ 700,000	800,000
Short-term Debt [Member] \| Industrial revenue bonds due April 1, 2028 [Member]
Debt Instrument [Line Items]
Hancock County industrial revenue bonds (IRBs) due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%))	$ 7,800,000	7,800,000
Maturity date	Apr. 01, 2028
Stated interest rate, percentage	5.63%
Short-term Debt [Member] \| Industrial revenue bonds due April 1, 2028 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Effective interest rate, maximum	12.00%
Short-term Debt [Member] \| Revolving credit facility [Member]
Debt Instrument [Line Items]
Stated interest rate, percentage	5.375%
Interest payable outstanding	$ 0
Principal payment	5,000,000.0
Interest payable	$ 700,000
Short-term Debt [Member] \| Revolving credit facility [Member] \| Revolving Credit Facility, Portion Subject To LIBOR Rate [Member]
Debt Instrument [Line Items]
Stated interest rate, percentage	1.68%
U.S. revolving credit facility [Member] \| Short-term Debt [Member] \| Revolving credit facility [Member]
Debt Instrument [Line Items]
Revolving credit facility	$ 45,000,000.0	4,000,000.0
Stated interest rate, percentage	3.50%
Iceland revolving line of credit [Member] \| Short-term Debt [Member] \| Revolving credit facility [Member]
Debt Instrument [Line Items]
Revolving credit facility	$ 45,000,000.0
Revolving credit facility	$ 45,000,000.0	$ 0
Stated interest rate, percentage	3.80%