XML 90 R74.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Pension and Other Postretirement Benefits - Weighted average assumptions used to determine net periodic benefit cost (Details) | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |
Rate of compensation increase, year one | 3.00% | 3.00% | 3.00%
Rate of compensation increase, year one and thereafter | 3.50% | 3.50% | 3.50%
Pension |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |
Measurement date | 12/31/2020 | 12/31/2019 | 12/31/2018
Fiscal year end | 12/31/2021 | 12/31/2020 | 12/31/2019
Discount rate | 2.77% | 3.22% | 4.38%
Rate of compensation increase, group 1 | 3.00% | 3.00% | 3.00%
Rate of compensation increase, group 2 | 3.50% | 3.50% | 3.50%
Expected return on plan assets | 7.25% | 7.25% | 7.25%
OPEB |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |  |
Measurement date | 12/31/2020 | 12/31/2019 | 12/31/2018
Fiscal year end | 12/31/2021 | 12/31/2020 | 12/31/2019
Discount rate | 1.89% | 2.79% | 4.29%
Rate of compensation increase, group 1 | 3.00% | 3.00% | 3.00%
Rate of compensation increase, group 2 | 3.50% | 3.50% | 3.50%
Expected return on plan assets | 0.00% | 0.00% | 0.00%

X
- Definition The maximum expected rate of compensation increases (for pay-related plans). + References No definition available. + Details
Name: | cenx_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncreaseMax
Namespace Prefix: | cenx_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase, Year One + References No definition available. + Details
Name: | cenx_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateofCompensationIncreaseYearOne
Namespace Prefix: | cenx_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase, Year One And Thereafter + References No definition available. + Details
Name: | cenx_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateofCompensationIncreaseYearOneAndThereafter
Namespace Prefix: | cenx_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Year end for fiscal year + References No definition available. + Details
Name: | cenx_FiscalYearEnd
Namespace Prefix: | cenx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The date(s) used to measure (at least the majority of) plan assets and benefit obligations for defined benefit pension and other postretirement benefit plans. + References No definition available. + Details
Name: | cenx_MeasurementDateNetPeriodicBenefitCost
Namespace Prefix: | cenx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2919-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(2) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
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_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

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