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Debt Industrial Revenue Bonds (Details) (Short-term Debt [Member], Industrial revenue bonds due 2028 [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Short-term Debt [Member] | Industrial revenue bonds due 2028 [Member]
Short-term Debt [Line Items]
Variable interest rates, maximum (as a percent)	12.00%us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMaximum / us-gaap_DebtInstrumentAxis = cenx_IndustrialRevenueBondsDue2028Member / us-gaap_ShortTermDebtTypeAxis = us-gaap_ShortTermDebtMember	12.00%us-gaap_DebtInstrumentInterestRateEffectivePercentageRateRangeMaximum / us-gaap_DebtInstrumentAxis = cenx_IndustrialRevenueBondsDue2028Member / us-gaap_ShortTermDebtTypeAxis = us-gaap_ShortTermDebtMember

X

- Definition

When presenting a range of interest rates, the highest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_ShortTermDebtLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration