XML 112 R83.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Pension and Other Postretirement Benefits - Pension Plan Asset Allocation (Details) | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocation percentage of assets | 100.00% |
Actual plan asset allocations | 100.00% | 100.00%
Global equity |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocation percentage of assets | 50.00% |
Actual plan asset allocations | 44.00% | 46.00%
Diversified credit |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocation percentage of assets | 15.00% |
Actual plan asset allocations | 15.00% | 19.00%
Real assets |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocation percentage of assets | 10.00% |
Actual plan asset allocations | 10.00% | 14.00%
Liability hedging assets |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocation percentage of assets | 25.00% |
Actual plan asset allocations | 28.00% | 21.00%
Cash |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocation percentage of assets | 0.00% |
Actual plan asset allocations | 3.00% | 0.00%

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

X
- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=cenx_GlobalEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=cenx_DiversifiedCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=cenx_RealAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=cenx_LiabilityHedgingAssetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |