XML 41 R31.htm IDEA: XBRL DOCUMENT
v3.10.0.1

General (Details) | 6 Months Ended
--- | ---
Jun. 30, 2018 pot_line
Hawesville [Member] |
Segment Reporting Information [Line Items] |
Number of pot lines | 5

X
- Definition Number of Pot Lines + References No definition available. + Details
Name: | cenx_NumberofPotLines
Namespace Prefix: | cenx_
Data Type: | xbrli:integerItemType
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_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_CounterpartyNameAxis=cenx_HawesvilleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |