XML 236 R85.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Pension and Other Postretirement Benefits - Assumed health care trend rates (Details) | Dec. 31, 2024
--- | ---
United States |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |
Medical cost inflation, years 13 and thereafter | 4.50%
Pre 65 | United States |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |
Medical cost inflation rate | 8.50%
Pre 65 | Jamaica |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |
Medical cost inflation rate | 8.00%
Post 65 | United States |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |
Medical cost inflation rate | 7.50%
Post 65 | Jamaica |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |
Medical cost inflation rate | 8.00%

X
- Definition Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (l) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Ultimate trend rate for health care cost for defined benefit postretirement plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (l) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanUltimateHealthCareCostTrendRate1
Namespace Prefix: | us-gaap_
Data Type: | dtr-types: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_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanSponsorLocationAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=cenx_PlanMembersPreAge65Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanSponsorLocationAxis=country_JM
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=cenx_PlanMembersPostAge65Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |