XML 58 R43.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Summary of significant accounting policies (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Glencore beneficial ownership |  | 42.90% |  |  |
Glencore economic ownership |  | 47.50% |  |  |
Allowance for doubtful accounts receivable | $ 1,000 | $ 1,000 | $ 1,000 |  |
BHH impairment |  | $ 0 | 11,584 | $ 0 |
Minimum [Member] | Building and Improvements [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Useful life |  | 10 years |  |  |
Minimum [Member] | Machinery and Equipment [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Useful life |  | 5 years |  |  |
Minimum [Member] | Technology and Software [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Useful life |  | 3 years |  |  |
Maximum [Member] | Building and Improvements [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Useful life |  | 45 years |  |  |
Maximum [Member] | Machinery and Equipment [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Useful life |  | 35 years |  |  |
Maximum [Member] | Technology and Software [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Useful life |  | 7 years |  |  |
Baise Haohi Carbon Co Ltd [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership percentage, equity method |  | 40.00% |  |  |
BHH [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership percentage, equity method |  | 40.00% |  |  |
BHH impairment | $ 11,584 |  |  |  |
Retained Earnings [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Adjustment to beginning retained earnings as of December 31, 2013 |  |  |  |  | $ 9,059
Deferred Tax Liability [Member] |  |  |  |  |
Property, Plant and Equipment [Line Items] |  |  |  |  |
Adjustment to beginning retained earnings as of December 31, 2013 |  |  | $ 9,059 |  |

X
- Definition The percentage of common stock and preferred stock of the company owned by a related party. + References No definition available. + Details
Name: | cenx_EconomicOwnershipPercentageByRelatedParty
Namespace Prefix: | cenx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5074-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.4) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_AllowanceForDoubtfulAccountsReceivable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 35 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=64825282&loc=d3e32787-111569 + Details
Name: | us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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=66011266&loc=d3e33918-111571 + Details
Name: | us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
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
Name: | us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of each individual error being corrected in the correcting adjustment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 1.N) -URI http://asc.fasb.org/extlink&oid=26874127&loc=d3e30840-122693 + Details
Name: | us-gaap_QuantifyingMisstatementInCurrentYearFinancialStatementsAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingAndBuildingImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_MachineryAndEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=cenx_TechnologyandSoftwareMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=cenx_BaiseHaohiCarbonCoLtdMember
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: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=cenx_DeferredTaxLiabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |