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v2.4.1.9

Subsequent events Subsequent events (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended | 41 Months Ended | 2 Months Ended |
--- | --- | --- | --- | ---
Dec. 31, 2012 | Dec. 31, 2014 | Feb. 27, 2015 | Feb. 26, 2015
Subsequent Event [Line Items] |  |  |  |
Treasury stock acquired, Aggregate purchase price | $ 4,033 us-gaap_TreasuryStockValueAcquiredCostMethod | $ 49,924 us-gaap_TreasuryStockValueAcquiredCostMethod |  |
Stock repurchase program, Remaining authorized repurchase amount |  | 10,076 us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1 |  |
Share repurchase program expansion [Member] |  |  |  |
Subsequent Event [Line Items] |  |  |  |
Stock Repurchase Program, Additional authorized amount |  |  |  | 20,000 cenx_StockRepurchaseProgramAdditionalAuthorizedAmount / us-gaap_SubsequentEventTypeAxis = cenx_SharerepurchaseprogramexpansionMember
Treasury stock acquired, Aggregate purchase price |  |  | 5,840 us-gaap_TreasuryStockValueAcquiredCostMethod / us-gaap_SubsequentEventTypeAxis = cenx_SharerepurchaseprogramexpansionMember |
Stock repurchase program, Remaining authorized repurchase amount |  |  |  | $ 24,276 us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1 / us-gaap_SubsequentEventTypeAxis = cenx_SharerepurchaseprogramexpansionMember

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- Definition Amount of additional stock repurchase plan authorization. + References No definition available. + Details
Name: | cenx_StockRepurchaseProgramAdditionalAuthorizedAmount
Namespace Prefix: | cenx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount remaining of a stock repurchase plan authorized. + References No definition available. + Details
Name: | us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
Name: | us-gaap_TreasuryStockValueAcquiredCostMethod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |