XML 94 R83.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Pension and other postretirement benefits - Company matching contribution to defined contribution 401(K) plans (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract] |  |  |
Age requirement for future accruals | 50 years |  |
Company matching contribution to defined contribution (401(k)) plans | $ 3,945 | $ 5,446 | $ 1,547

X
- Definition Defined Contribution Plan, Age Requirement for Future Accruals + References No definition available. + Details
Name: | cenx_DefinedContributionPlanAgeRequirementforFutureAccruals
Namespace Prefix: | cenx_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_CompensationAndRetirementDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration