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Fair value measurements Level 3 Transfers (Policies)	9 Months Ended
	Sep. 30, 2013
Fair Value Level 3 Transfer Disclosure [Abstract]
Fair Value Transfer, Policy [Policy Text Block]	It is our policy to recognize transfers into and transfers out of Level 3 as of the actual date of the event or change in circumstances that caused the transfer.

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- Details

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Namespace Prefix:	cenx_
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- Definition

Disclosure of accounting policy for determining when transfers between levels are recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(3)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

+ Details

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