XML 58 R47.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Derivatives (Details) $ in Thousands | 3 Months Ended
--- | ---
Mar. 31, 2017 USD ($) MWh t | Mar. 31, 2016 USD ($)
Derivative [Line Items] |  |
Derivative asset | $ | $ 1,610 |
Derivative liability | $ | 14,915 |
Recognized loss on derivative instruments | $ | $ 16,137 | $ (353)
LME Swap [Member] |  |
Derivative [Line Items] |  |
Other forward delivery contracts to sell primary aluminum (in tonnes) | 52,590 |
Other forward delivery contracts to sell primary aluminum, settled monthly (in tonnes) | 49,500 |
Price Swap [Member] |  |
Derivative [Line Items] |  |
Open position to offset fixed prices | 7,931 |
Affiliated Entity [Member] | LME Swap [Member] |  |
Derivative [Line Items] |  |
Other forward delivery contracts to sell primary aluminum (in tonnes) | 48,540 |
Grundartangi [Member] | Power Price Swap [Member] |  |
Derivative [Line Items] |  |
Percentage of power purchases included in forward price contract (percent) | 4.00% |
Power available | MWh | 256,200 |

X
- Definition Derivative, Financial Contract, Percentage + References No definition available. + Details
Name: | cenx_DerivativeFinancialContractPercentage
Namespace Prefix: | cenx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Total amount of primary aluminum committed to be supplied under existing contracts or agreements outside of major long-term supply commitments. + References No definition available. + Details
Name: | cenx_OtherPrimaryAluminumDeliveryCommitmentsAndContractsVolume
Namespace Prefix: | cenx_
Data Type: | num:massItemType
Balance Type: | na
Period Type: | instant

X
- Definition Other Primary Aluminum Delivery Commitments And Contracts Volume, Monthly Settlement Amount + References No definition available. + Details
Name: | cenx_OtherPrimaryAluminumDeliveryCommitmentsAndContractsVolumeMonthlySettlementAmount
Namespace Prefix: | cenx_
Data Type: | num:massItemType
Balance Type: | na
Period Type: | instant

X
- Definition The power currently available under the power purchase agreement. + References No definition available. + Details
Name: | cenx_PowerAvailable
Namespace Prefix: | cenx_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13495-108611 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313 + Details
Name: | us-gaap_DerivativeAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13495-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 + Details
Name: | us-gaap_DerivativeLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Nominal mass used to calculate payments on a derivative instrument. + References No definition available. + Details
Name: | us-gaap_DerivativeNonmonetaryNotionalAmountMass
Namespace Prefix: | us-gaap_
Data Type: | num:massItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959 + Details
Name: | us-gaap_GainLossOnDerivativeInstrumentsNetPretax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=cenx_FixedtoVariableLondonMetalsExchangeSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=cenx_FixedtoFloatingSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_AffiliatedEntityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=cenx_GrundartangiMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=cenx_PowerPriceSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |