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: