Subsequent events	3 Months Ended
Mar. 31, 2013
Subsequent Events [Abstract]
Subsequent events	Subsequent events We have evaluated all subsequent events through the date the financial statements were issued. Agreement to purchase Sebree smelter On April 29, 2013, we announced that our wholly owned subsidiary, Century Aluminum Sebree LLC ("Century Sebree"), had entered into a definitive agreement to acquire substantially all of the assets of the Sebree aluminum smelter from a subsidiary of Rio Tinto Alcan, Inc ("RTA"). Sebree, located in Kentucky, USA has an annual hot metal production capacity of 205,000 metric tons of primary aluminum and employs over 500 men and women. Century Sebree will acquire the smelter for approximately $61,000 in cash, after taking into account a $4,000 purchase price reduction relating to certain assumed retiree medical obligations, and will receive $71,000 in working capital, subject to customary adjustments. As part of the transaction, RTA will retain all historical environmental liabilities of the Sebree smelter and has agreed to fully fund the pension plan being assumed by Century at closing. The transaction is subject to certain closing conditions, including the consent of Kenergy Corp. to the assignment of the smelter's existing power contract, which will terminate on January 31, 2014. Tentative agreement on framework for market priced power for Hawesville On April 29, 2013, CAKY announced that it had reached a tentative agreement on the framework for providing market priced power to the Hawesville smelter. Under the arrangement, the power companies would purchase power on the open market and pass it through Hawesville at the market price plus additional costs incurred by them. The framework is subject to the negotiation of definitive agreements and approvals from various third parties, including the boards of directors of all parties, the Kentucky Public Service Commission ("KPSC"), the Rural Utilities Service and others. The parties intend to move as expeditiously as possible to finalize the agreement in advance of the expiration of the current power contract on August 20, 2013. Conditional WARN Notice and notice to terminate Southwire Metal Agreement at Hawesville On April 16, 2013, CAKY issued a conditional notice to the employees at the Hawesville smelter of its intent to curtail all plant operations effective August 20, 2013 if Hawesville cannot secure a competitively priced definitive power contract. The announcement was made pursuant to the federal Worker Adjustment and Retraining Notification Act ("WARN"). CAKY also gave notice to terminate its supply contract with its largest customer, the Southwire Company. The WARN notice specifies that the plant will be curtailed unless Hawesville can gain access to competitively priced electric power. Ingram settlement In February 2010, our subsidiary, CAWV, was named as a defendant in a lawsuit filed by Ingram alleging that CAWV breached two barging contracts with Ingram. In May 2013, the parties entered into a settlement agreement pursuant to which CAWV agreed to pay Ingram $1,575 and made certain commitments to Ingram with respect to future contracts. PBGC settlement agreement In April 2013, CAWV entered into a settlement agreement with the PBGC regarding an alleged “cessation of operations” at its Ravenswood facility as a result of the curtailment of operations at the facility. While CAWV does not believe that a “cessation of operations” has occurred, CAWV has reached an agreement with the PBGC to resolve the matter. Pursuant to the terms of the agreement, CAWV will make additional contributions (above any minimum required contributions) to its defined benefit pension plans totaling approximately $17,400 over the term of the agreement, which runs through 2016. In April 2013, CAWV made the first scheduled contribution pursuant to this agreement of $5,900. We expect to make additional annual contributions through 2016 totaling approximately $11,500. Under certain conditions, the contributions schedule could be accelerated by one year, so that the remaining contributions would be made through 2015.

Subsequent events

We have evaluated all subsequent events through the date the financial statements were issued.

Agreement to purchase Sebree smelter

On April 29, 2013, we announced that our wholly owned subsidiary, Century Aluminum Sebree LLC ("Century Sebree"), had entered into a definitive agreement to acquire substantially all of the assets of the Sebree aluminum smelter from a subsidiary of Rio Tinto Alcan, Inc ("RTA"). Sebree, located in Kentucky, USA has an annual hot metal production capacity of 205,000 metric tons of primary aluminum and employs over 500 men and women.

Century Sebree will acquire the smelter for approximately $61,000 in cash, after taking into account a $4,000 purchase price reduction relating to certain assumed retiree medical obligations, and will receive $71,000 in working capital, subject to customary adjustments. As part of the transaction, RTA will retain all historical environmental liabilities of the Sebree smelter and has agreed to fully fund the pension plan being assumed by Century at closing. The transaction is subject to certain closing conditions, including the consent of Kenergy Corp. to the assignment of the smelter's existing power contract, which will terminate on January 31, 2014.

Tentative agreement on framework for market priced power for Hawesville

On April 29, 2013, CAKY announced that it had reached a tentative agreement on the framework for providing market priced power to the Hawesville smelter. Under the arrangement, the power companies would purchase power on the open market and pass it through Hawesville at the market price plus additional costs incurred by them. The framework is subject to the negotiation of definitive agreements and approvals from various third parties, including the boards of directors of all parties, the Kentucky Public Service Commission ("KPSC"), the Rural Utilities Service and others. The parties intend to move as expeditiously as possible to finalize the agreement in advance of the expiration of the current power contract on August 20, 2013.

Conditional WARN Notice and notice to terminate Southwire Metal Agreement at Hawesville

On April 16, 2013, CAKY issued a conditional notice to the employees at the Hawesville smelter of its intent to curtail all plant operations effective August 20, 2013 if Hawesville cannot secure a competitively priced definitive power contract. The announcement was made pursuant to the federal Worker Adjustment and Retraining Notification Act ("WARN"). CAKY also gave notice to terminate its supply contract with its largest customer, the Southwire Company. The WARN notice specifies that the plant will be curtailed unless Hawesville can gain access to competitively priced electric power.

Ingram settlement

In February 2010, our subsidiary, CAWV, was named as a defendant in a lawsuit filed by Ingram alleging that CAWV breached two barging contracts with Ingram. In May 2013, the parties entered into a settlement agreement pursuant to which CAWV agreed to pay Ingram $1,575 and made certain commitments to Ingram with respect to future contracts.

PBGC settlement agreement

In April 2013, CAWV entered into a settlement agreement with the PBGC regarding an alleged “cessation of operations” at its Ravenswood facility as a result of the curtailment of operations at the facility. While CAWV does not believe that a “cessation of operations” has occurred, CAWV has reached an agreement with the PBGC to resolve the matter. Pursuant to the terms of the agreement, CAWV will make additional contributions (above any minimum required contributions) to its defined benefit pension plans totaling approximately $17,400 over the term of the agreement, which runs through 2016. In April 2013, CAWV made the first scheduled contribution pursuant to this agreement of $5,900. We expect to make additional annual contributions through 2016 totaling approximately $11,500. Under certain conditions, the contributions schedule could be accelerated by one year, so that the remaining contributions would be made through 2015.