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Pension and Other Postretirement Benefits Weighted Average assumptions used in calculating benefit obligations (Details)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.89%		4.00%
Rate of compensation increase, first five years	3.00%	[1]	3.00%	[1]
Rate of compensation increase, year six and thereafter	4.00%	[1]	4.00%	[1]
Measurement date	12/31/2013		12/31/2012
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.99%		3.98%
Rate of compensation increase, first five years	3.00%	[1]	3.00%	[1]
Rate of compensation increase, year six and thereafter	4.00%	[1]	4.00%	[1]
Measurement date	12/31/2013		12/31/2012
[1] Rate of compensation increase assumption is 3% per year for first five years and then 4% per year for year six and thereafter.

X

- Definition

The mid expected rate of compensation increases (for pay-related plans).

+ References

No definition available.

+ Details

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Namespace Prefix:	cenx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The interest rate used to adjust for the time value of money for the plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Expected rate of compensation increases (for pay-related plans).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(2)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The date(s) used to measure (at least the majority of) plan assets and benefit obligations for defined benefit pension and other postretirement benefit plans. Disclosure required by FAS 132R paragraph 5k prior to being amended by FAS 158.

+ References

No definition available.

+ Details

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

X

- Details

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