XML 48 R36.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Business acquisitions - Acquisition of Mt. Holly smelter narrative other units (Details) t in Thousands | Dec. 01, 2014 employee t | Nov. 30, 2014
--- | --- | ---
Mt. Holly Smelter [Member] |  |
Business Acquisition [Line Items] |  |
Remaining percentage acquired in step acquisition |  | 50.30%
Percentage of ownership after step acquisition | 100.00% |
Employees | employee | 600 |
Mt Holly primary aluminum capacity (tonnes) | t | 231 |
Mt. Holly [Member] | Berkeley Aluminum Inc. [Member] |  |
Business Acquisition [Line Items] |  |
Ownership percentage |  | 49.70%

X
- Definition Percentage of ownership at the acquisition date as a result of the business combination. + References No definition available. + Details
Name: | cenx_BusinessAcquisitionPercentageofOwnershipAfterAcquisition
Namespace Prefix: | cenx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Annual production capacity of primary aluminum (in tonnes). + References No definition available. + Details
Name: | cenx_Primaryaluminumcapacity
Namespace Prefix: | cenx_
Data Type: | num:massItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of persons employed by the Entity + References No definition available. + Details
Name: | dei_EntityNumberOfEmployees
Namespace Prefix: | dei_
Data Type: | xbrli:decimalItemType
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
Name: | us-gaap_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of voting equity interests acquired in a business combination achieved in stages, including equity interests in the acquiree held by the acquirer immediately before the acquisition date and acquired at the acquisition date. + References No definition available. + Details
Name: | us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeIncludingSubsequentAcquisitionPercentage
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
Name: | us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=cenx_Mt.HollySmelterMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=cenx_Mt.HollyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=us-gaap_SubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |