XML 13 R39.htm IDEA: XBRL DOCUMENT v3.3.0.814

Related party transactions - Narrative (Details)	Sep. 30, 2015
Glencore [Member]
Related Party Transaction [Line Items]
Ownership percentage by majority shareholder	47.60%
BHH [Member]
Related Party Transaction [Line Items]
Ownership percentage	40.00%

X

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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



-Publisher FASB



-Name Accounting Standards Codification



-Topic 323



-SubTopic 10



-Section 50



-Paragraph 3



-Subparagraph (a)(1)



-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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

X

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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

X

- 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

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

X

- Details

Name:	dei_LegalEntityAxis=cenx_GlencoreMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=cenx_BhhMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: