Debt Instrument, Payment Terms, Number of Monthly Payments

No definition available.

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Data Type:	xbrli:integerItemType
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Period Type:	duration

- Definition

The amount of additional borrowings provided in credit facility under a letter of credit sub-facility.

+ References

No definition available.

+ Details

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

- Definition

Line of Credit Facility, Remaining Borrowing Capacity, Net of Letters of Credit

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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

- Definition

Carrying amount as of the balance sheet date of obligations due all related parties.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
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-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.15(3),(4))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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

Name:	us-gaap_LineOfCreditFacilityLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Details

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- Details

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Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_DomesticLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_ForeignLineOfCreditMember
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- Details

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Debt - Credit Facility (Details)	Apr. 29, 2019 USD ($) installment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Hawesville [Member]
Line of Credit Facility [Line Items]
Due to Related Parties	$ 40,000,000.0
Number of monthly payments \| installment	24
Hawesville [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	5.375%
U.S revolving credit facility [Member]
Line of Credit Facility [Line Items]
Credit facility maximum amount		$ 175,000,000.0
Borrowing availability		157,000,000.0
Outstanding letters of credit issued		41,400,000
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Letter of credit sub-facility amount		111,600,000
Long-term Debt [Member] \| U.S revolving credit facility [Member]
Line of Credit Facility [Line Items]
Credit facility face amount		175,000,000.0
Long-term Debt [Member] \| Letter of Credit [Member]
Line of Credit Facility [Line Items]
Letter of credit sub-facility amount		110,000,000.0
Long-term Debt [Member] \| U.S revolving credit facility, accordion [Member]
Line of Credit Facility [Line Items]
Credit facility face amount		50,000,000.0
Long-term Debt [Member] \| Iceland revolving credit facility [Member]
Line of Credit Facility [Line Items]
Credit facility maximum amount		50,000,000.0
Borrowing availability		50,000,000.0
Outstanding letters of credit issued		0
Borrowing availability, net of outstanding letters of credit and borrowings		50,000,000.0
Short-term Debt [Member] \| Letter of Credit [Member]
Line of Credit Facility [Line Items]
Outstanding borrowings		4,000,000.0	$ 23,300,000
Short-term Debt [Member] \| Iceland revolving credit facility [Member]
Line of Credit Facility [Line Items]
Outstanding borrowings		$ 0