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Pension and Other Postretirement Benefits Discount Rate Change in Estimate (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Basis point change to discount rate (in basis points)	25
Pension Obligation due to change in discount rate	$ 10,000

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- Definition

Basis point change to pension plan assumption discount rate used in calculating the net periodic cost.

+ References

No definition available.

+ Details

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X

- Definition

Pension Obligation due to change in discount rate in pension plan assumption used in calculating the net periodic cost

+ References

No definition available.

+ Details

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

X

- Details

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