XML 72 R26.htm IDEA: XBRL DOCUMENT v2.4.1.9

Fair value measurements Level 3 Transfers (Policies)	3 Months Ended
	Mar. 31, 2015
Fair Value Level 3 Transfer Disclosure [Abstract]
Fair Value Level 3 Transfer Policy	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.

X

- Details

Name:	cenx_FairValueLevel3TransferDisclosureAbstract
Namespace Prefix:	cenx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- 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=36462937&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=36462937&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueTransferPolicyPolicyTextBlock
Namespace Prefix:	us-gaap_
Data Type:	nonnum:textBlockItemType
Balance Type:	na
Period Type:	duration