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Commitments and contingencies Ravenswood Retiree Medical Benefits changes (Details) (PBGC Agreement [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended	45 Months Ended
	Dec. 31, 2013	Dec. 31, 2016
PBGC Agreement [Member]
Loss Contingencies [Line Items]
Pension Contributions Above Required Minimum, Total		$ 17,400
Pension Contributions	$ 6,700

X

- Definition

Pursuant to the terms of the settlement agreement with the Pension Benefit Guaranty Corporation, we will make additional contributions (above any minimum required contributions) to our defined benefit pension plans.

+ References

No definition available.

+ Details

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Namespace Prefix:	cenx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The amount of cash or cash equivalents contributed by the entity to fund its pension plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 25

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585

+ Details

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