Curtailment of Operations - Hawesville	12 Months Ended
Dec. 31, 2022
Restructuring and Related Activities [Abstract]
Curtailment of Operations - Hawesville	Curtailment of Operations - HawesvilleOn June 22, 2022, our subsidiary, Century Aluminum of Kentucky ("CAKY"), issued a Worker Adjustment and Retraining Notification Act ("WARN") notice at its Hawesville, Kentucky aluminum smelter related to a temporary curtailment of plant operations within 60 days as a result of current market conditions, including historically high energy costs and declining London Metal Exchange ("LME") prices. We have since fully curtailed production at the facility and expect to continue to maintain the plant with the intention of restarting operations when market conditions permit, including energy prices returning to more normalized levels and aluminum prices maintaining levels that can support the on-going costs and capital expenditures necessary to restart and operate the plant. As the curtailment represents a significant adverse change in the extent and manner in which the Hawesville smelter will be used, we accordingly evaluated the Hawesville asset group for recoverability. As the carrying value of the Hawesville asset group was determined to not be recoverable based on the estimated undiscounted cash flows expected to be generated over the life of the asset group, an impairment charge of $159.4 million was recognized to write down the asset group to its estimated fair value of $15.0 million. We classified the estimated remaining fair value of the long lived assets within Level 3 of the fair value hierarchy as its fair value was determined based on recent comparable transactions with inputs that are not readily observable in the market. We recognized approximately $18.1 million of expense during the year related to wages and severance triggered by our issuance of the WARN notice and excess capacity charges, partially offset by final plant idling activities. We also recognized a non-cash other postretirement benefits ("OPEB") curtailment gain totaling $8.9 million for the year ended December 31, 2022. See Note 12. Pension and other postretirement benefits to the consolidated financial statements included herein for additional information.

Curtailment of Operations - Hawesville

12 Months Ended

Dec. 31, 2022

Restructuring and Related Activities [Abstract]

Curtailment of Operations - HawesvilleOn June 22, 2022, our subsidiary, Century Aluminum of Kentucky ("CAKY"), issued a Worker Adjustment and Retraining Notification Act ("WARN") notice at its Hawesville, Kentucky aluminum smelter related to a temporary curtailment of plant operations within 60 days as a result of current market conditions, including historically high energy costs and declining London Metal Exchange ("LME") prices. We have since fully curtailed production at the facility and expect to continue to maintain the plant with the intention of restarting operations when market conditions permit, including energy prices returning to more normalized levels and aluminum prices maintaining levels that can support the on-going costs and capital expenditures necessary to restart and operate the plant. As the curtailment represents a significant adverse change in the extent and manner in which the Hawesville smelter will be used, we accordingly evaluated the Hawesville asset group for recoverability. As the carrying value of the Hawesville asset group was determined to not be recoverable based on the estimated undiscounted cash flows expected to be generated over the life of the asset group, an impairment charge of $159.4 million was recognized to write down the asset group to its estimated fair value of $15.0 million. We classified the estimated remaining fair value of the long lived assets within Level 3 of the fair value hierarchy as its fair value was determined based on recent comparable transactions with inputs that are not readily observable in the market. We recognized approximately $18.1 million of expense during the year related to wages and severance triggered by our issuance of the WARN notice and excess capacity charges, partially offset by final plant idling activities. We also recognized a non-cash other postretirement benefits ("OPEB") curtailment gain totaling $8.9 million for the year ended December 31, 2022. See Note 12. Pension and other postretirement benefits to the consolidated financial statements included herein for additional information.