Commitments and contingencies	6 Months Ended
Jun. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	Commitments and contingencies Environmental Contingencies Based upon all available information, we believe our current environmental liabilities do not have, and are not likely to have, a material adverse effect on our financial condition, results of operations or liquidity. However, because of the inherent uncertainties in estimating environmental liabilities primarily due to unknown facts and circumstances and changing governmental regulations and legal standards regarding liability, there can be no assurance that future capital expenditures and costs for environmental compliance at currently or formerly owned or operated properties will not result in liabilities that may have a material adverse effect on our financial condition, results of operations or liquidity. It is our policy to accrue for costs associated with environmental assessments and remedial efforts when it becomes probable that a liability has been incurred and the costs can be reasonably estimated. The aggregate environmental-related accrued liabilities were $1,383 and $1,112 at June 30, 2016 and December 31, 2015, respectively. All accrued amounts have been recorded without giving effect to any possible future recoveries. Costs for ongoing environmental compliance, including maintenance and monitoring are expensed as incurred. In July 2006, we were named as a defendant, together with certain affiliates of Alcan Inc., in a lawsuit brought by Alcoa Inc. seeking to determine responsibility for certain environmental indemnity obligations related to the sale of a cast aluminum plate manufacturing facility located in Vernon, California, which we purchased from Alcoa Inc. in December 1998, and sold to Alcan Rolled Products-Ravenswood LLC in July 1999. The complaint also seeks costs and attorney fees. The matter was stayed by the court in 2008 to allow for the remediation of environmental areas at the site. On June 30, 2016 the court ordered the stay lifted and reopened the case. The matter is in a preliminary stage in the U.S. District Court for the District of Delaware, and we cannot predict the ultimate outcome of this action or estimate a range of possible losses related to this matter at this time. Matters relating to the St. Croix Alumina Refining Facility We are a party to a United States Environmental Protection Agency Administrative Order on Consent (the "Order") pursuant to which certain past and present owners of an alumina refining facility at St. Croix, Virgin Islands (the "St. Croix Alumina Refinery") have agreed to carry out a Hydrocarbon Recovery Plan to remove and manage hydrocarbons floating on groundwater underlying the facility. Pursuant to the Hydrocarbon Recovery Plan, recovered hydrocarbons and groundwater are delivered to the adjacent petroleum refinery where they are received and managed. In connection with the sale of the facility by Lockheed Martin Corporation ("Lockheed") to one of our affiliates, Virgin Islands Alumina Corporation ("Vialco"), in 1989, Lockheed, Vialco and Century entered into the Lockheed-Vialco Asset Purchase Agreement. The indemnity provisions contained in the Lockheed-Vialco Asset Purchase Agreement allocate responsibility for certain environmental matters. Lockheed has tendered indemnity to Vialco. We have likewise tendered indemnity to Lockheed. Through June 30, 2016, we have expended approximately $1,085 on the Hydrocarbon Recovery Plan. At this time, we are not able to estimate the amount of any future potential payments under this indemnification to comply with the Order, but we do not anticipate that any such amounts will have a material adverse effect on our financial condition, results of operations or liquidity, regardless of the final outcome. Vialco sold the St. Croix Alumina Refinery to St. Croix Alumina, LLC, a subsidiary of Alcoa, in 1995. In December 2010, Century was among several defendants named in a lawsuit filed by plaintiffs who either worked, resided or owned property in the area downwind from the St. Croix Alumina Refinery. In March 2011, Century was also named a defendant in a nearly identical suit brought by certain additional plaintiffs. The plaintiffs in both suits allege damages caused by the presence of red mud and other particulates coming from the alumina facility and are seeking unspecified monetary damages, costs and attorney fees as well as certain injunctive relief. We tendered indemnity and defense to St. Croix Alumina LLC and Alcoa Alumina & Chemical LLC under the terms of an acquisition agreement relating to the facility and have filed motions to dismiss plaintiffs’ claims. In August 2015, the Superior Court of the Virgin Islands, Division of St. Croix denied the motions to dismiss but ordered all plaintiffs to refile individual complaints. At this time, it is not possible to predict the ultimate outcome of or to estimate a range of possible losses for any of the foregoing actions relating to the St. Croix Alumina Refinery. Legal Contingencies In addition to the foregoing matters, we have pending against us or may be subject to various lawsuits, claims and proceedings related primarily to employment, commercial, stockholder, safety and health matters. While the results of such litigation matters and claims cannot be predicted with certainty, we believe that the final outcome of such matters will not have a material adverse impact on our financial condition, results of operations or liquidity. However, because of the nature and inherent uncertainties of litigation, should the outcome of these actions be unfavorable, our business, financial condition, results of operations and liquidity could be materially and adversely affected. In evaluating whether to accrue for losses associated with legal contingencies, it is our policy to take into consideration factors such as the facts and circumstances asserted, our historical experience with contingencies of a similar nature, the likelihood of our prevailing and the severity of any potential loss. For some matters, no accrual is established because we have assessed our risk of loss to be remote. Where the risk of loss is probable and the amount of the loss can be reasonably estimated, we record an accrual, either on an individual basis or with respect to a group of matters involving similar claims, based on the factors set forth above. When we have assessed that a loss associated with legal contingencies is reasonably possible, we determine if estimates of possible losses or ranges of possible losses are in excess of related accrued liabilities, if any. Based on current knowledge, management has ascertained estimates for losses that are reasonably possible and management does not believe that any reasonably possible outcomes in excess of our accruals, if any, either individually or in aggregate, would be material to our financial condition, results of operations or liquidity. We reevaluate and update our assessments and accruals as matters progress over time. Ravenswood Retiree Medical Benefits changes In November 2009, Century Aluminum of West Virginia ("CAWV") filed a class action complaint for declaratory judgment against the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union ("USW"), the USW’s local and certain CAWV retirees, individually and as class representatives, seeking a declaration of CAWV’s rights to modify/terminate retiree medical benefits. Later in November 2009, the USW and representatives of a retiree class filed a separate suit against CAWV, Century Aluminum Company, Century Aluminum Master Welfare Benefit Plan, and various John Does with respect to the foregoing. These actions, entitled Dewhurst, et al. v. Century Aluminum Co., et al., and Century Aluminum of West Virginia, Inc. v. United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union, AFL-CIO/CLC, et al., have been consolidated and venue has been set in the District Court for the Southern District of West Virginia. In September 2015, the trial court granted CAWV's motion for summary judgment of these actions. The trial court decision is currently being appealed by the USW to the Court of Appeals for the 4th Circuit. PBGC Settlement In April 2013, we entered into a settlement agreement with the Pension Benefit Guarantee Corporation ("PBGC") regarding an alleged "cessation of operations" at our Ravenswood facility as a result of the curtailment of operations at the facility and, pursuant to the agreement, we agreed to make additional contributions (above any minimum required contributions) to our defined benefit pension plans totaling approximately $17.4 million. The agreement permits us to defer payments during periods of lower primary aluminum prices relative to our cost of operations. We remeasure aluminum prices against our cost of operations on an annual basis based on our fourth quarter results. To the extent that we elect to defer one or more of these payments, we are required to provide the PBGC with acceptable security for any such deferred payments. We made contributions pursuant to this agreement of $1.1 million in March 2015 and $6.7 million in 2013. We did not make any contributions during 2014 and have not made any contributions in 2016 through June 30. The remaining contributions under this agreement are approximately $9.6 million. Power Commitments and Contingencies Hawesville Hawesville has a power supply arrangement with Kenergy and EDF Trading North America, LLC (“EDF") which provides market-based power to the Hawesville smelter. Under this arrangement, the power companies purchase power on the open market and pass it through to Hawesville at Midcontinent Independent System Operator ("MISO") pricing plus transmission and other costs. The power supply arrangement with Kenergy has an effective term through December 2023. The arrangement with EDF to act as our market participant with MISO has an effective term through May 2017, extending year to year thereafter unless a one year notice is given. Sebree Sebree has a power supply arrangement with Kenergy and EDF which provides market-based power to the Sebree smelter. Similar to the arrangement at Hawesville, the power companies purchase power on the open market and pass it through to Sebree at MISO pricing plus transmission and other costs. The power supply arrangement with Kenergy has an effective term through December 2023. The arrangement with EDF to act as our market participant with MISO has an effective term through May 2017, extending year to year thereafter unless a one year notice is given. Mt. Holly Mt. Holly has a power supply arrangement pursuant to which 25% of the Mt. Holly load is served from the South Carolina Public Service Authority’s ("Santee Cooper") generation at a standard cost-based industrial rate and 75% of the Mt. Holly load is sourced from a third party supplier from generation that is outside Santee Cooper’s service territory at market prices that are tied to natural gas prices. The agreement with Santee Cooper has a term through December 31, 2018 but can be terminated by CASC on 60 days' notice. Grundartangi Grundartangi has power purchase agreements with HS Orka hf ("HS"), Landsvirkjun and Orkuveita Reykjavikur ("OR") to provide power to its Grundartangi smelter. These power purchase agreements, which will expire on various dates from 2019 through 2036 (subject to extension), provide power at LME-based variable rates. Each power purchase agreement contains take-or-pay obligations with respect to a significant percentage of the total committed and available power under such agreement. Helguvik Nordural Helguvik ehf ("Helguvik") has power purchase agreements with HS and OR to provide power to the Helguvik project. These power purchase agreements provide power at LME-based variable rates and contain take-or-pay obligations with respect to a significant percentage of the total committed and available power under such agreements. The power purchase agreements contain certain conditions to HS’s and OR’s obligations. HS (with respect to all phases) and OR (with respect to all phases other than the first phase) have alleged that certain of these conditions have not been satisfied. The first stage of power under the OR power purchase agreement (approximately 47.5 MW) became available in the fourth quarter of 2011 and is currently being utilized at Grundartangi. In July 2014, HS commenced arbitration proceedings against Helguvik seeking, among other things, an order declaring, (i) that the conditions to the power contract have not been fulfilled and, (ii) that the power contract is therefore no longer valid. Arbitration hearings were held in April 2016 but the arbitral tribunal has yet to issue its decision. Other Commitments and Contingencies Labor Commitments The bargaining unit employees at our Grundartangi, Vlissingen, Hawesville, Sebree and Ravenswood facilities are represented by labor unions, representing 63% of our total workforce. Approximately 83% of Grundartangi’s work force is represented by five labor unions, governed by a labor agreement which is effective through December 31, 2019 that establishes wages and work rules for covered employees. 100% of Vlissingen's work force is represented by the Federation for the Metal and Electrical Industry ("FME") which negotiates working conditions with trade unions on behalf of its members. In March 2016, a new labor agreement was reached with the FME which is effective retroactively from May 1, 2015 to June 1, 2018. Approximately 53% of our U.S. based work force is represented by the USW. In June 2015, CAKY entered into a new collective bargaining agreement with the USW for its employees at the Hawesville smelter. The agreement is effective through April 1, 2020. Century Sebree, LLC has a collective bargaining agreement with the USW for its employees at the Sebree smelter that is effective through October 28, 2019. Our employees at Mt. Holly are not represented by a labor union.

Commitments and contingencies

Environmental Contingencies

Based upon all available information, we believe our current environmental liabilities do not have, and are not likely to have, a material adverse effect on our financial condition, results of operations or liquidity. However, because of the inherent uncertainties in estimating environmental liabilities primarily due to unknown facts and circumstances and changing governmental regulations and legal standards regarding liability, there can be no assurance that future capital expenditures and costs for environmental compliance at currently or formerly owned or operated properties will not result in liabilities that may have a material adverse effect on our financial condition, results of operations or liquidity.

It is our policy to accrue for costs associated with environmental assessments and remedial efforts when it becomes probable that a liability has been incurred and the costs can be reasonably estimated. The aggregate environmental-related accrued liabilities were $1,383 and $1,112 at June 30, 2016 and December 31, 2015, respectively. All accrued amounts have been recorded without giving effect to any possible future recoveries. Costs for ongoing environmental compliance, including maintenance and monitoring are expensed as incurred.

In July 2006, we were named as a defendant, together with certain affiliates of Alcan Inc., in a lawsuit brought by Alcoa Inc. seeking to determine responsibility for certain environmental indemnity obligations related to the sale of a cast aluminum plate manufacturing facility located in Vernon, California, which we purchased from Alcoa Inc. in December 1998, and sold to Alcan Rolled Products-Ravenswood LLC in July 1999. The complaint also seeks costs and attorney fees. The matter was stayed by the court in 2008 to allow for the remediation of environmental areas at the site. On June 30, 2016 the court ordered the stay lifted and reopened the case. The matter is in a preliminary stage in the U.S. District Court for the District of Delaware, and we cannot predict the ultimate outcome of this action or estimate a range of possible losses related to this matter at this time.

Matters relating to the St. Croix Alumina Refining Facility

We are a party to a United States Environmental Protection Agency Administrative Order on Consent (the "Order") pursuant to which certain past and present owners of an alumina refining facility at St. Croix, Virgin Islands (the "St. Croix Alumina Refinery") have agreed to carry out a Hydrocarbon Recovery Plan to remove and manage hydrocarbons floating on groundwater underlying the facility. Pursuant to the Hydrocarbon Recovery Plan, recovered hydrocarbons and groundwater are delivered to the adjacent petroleum refinery where they are received and managed. In connection with the sale of the facility by Lockheed Martin Corporation ("Lockheed") to one of our affiliates, Virgin Islands Alumina Corporation ("Vialco"), in 1989, Lockheed, Vialco and Century entered into the Lockheed-Vialco Asset Purchase Agreement. The indemnity provisions contained in the Lockheed-Vialco Asset Purchase Agreement allocate responsibility for certain environmental matters. Lockheed has tendered indemnity to Vialco. We have likewise tendered indemnity to Lockheed. Through June 30, 2016, we have expended approximately $1,085 on the Hydrocarbon Recovery Plan. At this time, we are not able to estimate the amount of any future potential payments under this indemnification to comply with the Order, but we do not anticipate that any such amounts will have a material adverse effect on our financial condition, results of operations or liquidity, regardless of the final outcome. Vialco sold the St. Croix Alumina Refinery to St. Croix Alumina, LLC, a subsidiary of Alcoa, in 1995.

In December 2010, Century was among several defendants named in a lawsuit filed by plaintiffs who either worked, resided or owned property in the area downwind from the St. Croix Alumina Refinery. In March 2011, Century was also named a defendant in a nearly identical suit brought by certain additional plaintiffs. The plaintiffs in both suits allege damages caused by the presence of red mud and other particulates coming from the alumina facility and are seeking unspecified monetary damages, costs and attorney fees as well as certain injunctive relief. We tendered indemnity and defense to St. Croix Alumina LLC and Alcoa Alumina & Chemical LLC under the terms of an acquisition agreement relating to the facility and have filed motions to dismiss plaintiffs’ claims. In August 2015, the Superior Court of the Virgin Islands, Division of St. Croix denied the motions to dismiss but ordered all plaintiffs to refile individual complaints. At this time, it is not possible to predict the ultimate outcome of or to estimate a range of possible losses for any of the foregoing actions relating to the St. Croix Alumina Refinery.

Legal Contingencies

In addition to the foregoing matters, we have pending against us or may be subject to various lawsuits, claims and proceedings related primarily to employment, commercial, stockholder, safety and health matters. While the results of such litigation matters and claims cannot be predicted with certainty, we believe that the final outcome of such matters will not have a material adverse impact on our financial condition, results of operations or liquidity. However, because of the nature and inherent uncertainties of litigation, should the outcome of these actions be unfavorable, our business, financial condition, results of operations and liquidity could be materially and adversely affected.

In evaluating whether to accrue for losses associated with legal contingencies, it is our policy to take into consideration factors such as the facts and circumstances asserted, our historical experience with contingencies of a similar nature, the likelihood of our prevailing and the severity of any potential loss. For some matters, no accrual is established because we have assessed our risk of loss to be remote. Where the risk of loss is probable and the amount of the loss can be reasonably estimated, we record an accrual, either on an individual basis or with respect to a group of matters involving similar claims, based on the factors set forth above.

When we have assessed that a loss associated with legal contingencies is reasonably possible, we determine if estimates of possible losses or ranges of possible losses are in excess of related accrued liabilities, if any. Based on current knowledge, management has ascertained estimates for losses that are reasonably possible and management does not believe that any reasonably possible outcomes in excess of our accruals, if any, either individually or in aggregate, would be material to our financial condition, results of operations or liquidity. We reevaluate and update our assessments and accruals as matters progress over time.

Ravenswood Retiree Medical Benefits changes

In November 2009, Century Aluminum of West Virginia ("CAWV") filed a class action complaint for declaratory judgment against the United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union ("USW"), the USW’s local and certain CAWV retirees, individually and as class representatives, seeking a declaration of CAWV’s rights to modify/terminate retiree medical benefits. Later in November 2009, the USW and representatives of a retiree class filed a separate suit against CAWV, Century Aluminum Company, Century Aluminum Master Welfare Benefit Plan, and various John Does with respect to the foregoing. These actions, entitled Dewhurst, et al. v. Century Aluminum Co., et al., and Century Aluminum of West Virginia, Inc. v. United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union, AFL-CIO/CLC, et al., have been consolidated and venue has been set in the District Court for the Southern District of West Virginia.

In September 2015, the trial court granted CAWV's motion for summary judgment of these actions. The trial court decision is currently being appealed by the USW to the Court of Appeals for the 4th Circuit.

PBGC Settlement

In April 2013, we entered into a settlement agreement with the Pension Benefit Guarantee Corporation ("PBGC") regarding an alleged "cessation of operations" at our Ravenswood facility as a result of the curtailment of operations at the facility and, pursuant to the agreement, we agreed to make additional contributions (above any minimum required contributions) to our defined benefit pension plans totaling approximately $17.4 million. The agreement permits us to defer payments during periods of lower primary aluminum prices relative to our cost of operations. We remeasure aluminum prices against our cost of operations on an annual basis based on our fourth quarter results. To the extent that we elect to defer one or more of these payments, we are required to provide the PBGC with acceptable security for any such deferred payments. We made contributions pursuant to this agreement of $1.1 million in March 2015 and $6.7 million in 2013. We did not make any contributions during 2014 and have not made any contributions in 2016 through June 30. The remaining contributions under this agreement are approximately $9.6 million.

Power Commitments and Contingencies

Hawesville

Hawesville has a power supply arrangement with Kenergy and EDF Trading North America, LLC (“EDF") which provides market-based power to the Hawesville smelter. Under this arrangement, the power companies purchase power on the open market and pass it through to Hawesville at Midcontinent Independent System Operator ("MISO") pricing plus transmission and other costs. The power supply arrangement with Kenergy has an effective term through December 2023. The arrangement with EDF to act as our market participant with MISO has an effective term through May 2017, extending year to year thereafter unless a one year notice is given.

Sebree

Sebree has a power supply arrangement with Kenergy and EDF which provides market-based power to the Sebree smelter. Similar to the arrangement at Hawesville, the power companies purchase power on the open market and pass it through to Sebree at MISO pricing plus transmission and other costs. The power supply arrangement with Kenergy has an effective term through December 2023. The arrangement with EDF to act as our market participant with MISO has an effective term through May 2017, extending year to year thereafter unless a one year notice is given.

Mt. Holly

Mt. Holly has a power supply arrangement pursuant to which 25% of the Mt. Holly load is served from the South Carolina Public Service Authority’s ("Santee Cooper") generation at a standard cost-based industrial rate and 75% of the Mt. Holly load is sourced from a third party supplier from generation that is outside Santee Cooper’s service territory at market prices that are tied to natural gas prices. The agreement with Santee Cooper has a term through December 31, 2018 but can be terminated by CASC on 60 days' notice.

Grundartangi

Grundartangi has power purchase agreements with HS Orka hf ("HS"), Landsvirkjun and Orkuveita Reykjavikur ("OR") to provide power to its Grundartangi smelter. These power purchase agreements, which will expire on various dates from 2019 through 2036 (subject to extension), provide power at LME-based variable rates. Each power purchase agreement contains take-or-pay obligations with respect to a significant percentage of the total committed and available power under such agreement.

Helguvik

Nordural Helguvik ehf ("Helguvik") has power purchase agreements with HS and OR to provide power to the Helguvik project. These power purchase agreements provide power at LME-based variable rates and contain take-or-pay obligations with respect to a significant percentage of the total committed and available power under such agreements. The power purchase agreements contain certain conditions to HS’s and OR’s obligations. HS (with respect to all phases) and OR (with respect to all phases other than the first phase) have alleged that certain of these conditions have not been satisfied. The first stage of power under the OR power purchase agreement (approximately 47.5 MW) became available in the fourth quarter of 2011 and is currently being utilized at Grundartangi. In July 2014, HS commenced arbitration proceedings against Helguvik seeking, among other things, an order declaring, (i) that the conditions to the power contract have not been fulfilled and, (ii) that the power contract is therefore no longer valid. Arbitration hearings were held in April 2016 but the arbitral tribunal has yet to issue its decision.

Other Commitments and Contingencies

Labor Commitments

The bargaining unit employees at our Grundartangi, Vlissingen, Hawesville, Sebree and Ravenswood facilities are represented by labor unions, representing 63% of our total workforce.

Approximately 83% of Grundartangi’s work force is represented by five labor unions, governed by a labor agreement which is effective through December 31, 2019 that establishes wages and work rules for covered employees. 100% of Vlissingen's work force is represented by the Federation for the Metal and Electrical Industry ("FME") which negotiates working conditions with trade unions on behalf of its members. In March 2016, a new labor agreement was reached with the FME which is effective retroactively from May 1, 2015 to June 1, 2018.

Approximately 53% of our U.S. based work force is represented by the USW. In June 2015, CAKY entered into a new collective bargaining agreement with the USW for its employees at the Hawesville smelter. The agreement is effective through April 1, 2020. Century Sebree, LLC has a collective bargaining agreement with the USW for its employees at the Sebree smelter that is effective through October 28, 2019. Our employees at Mt. Holly are not represented by a labor union.