Curtailment of Operations - Hawesville	9 Months Ended
	Sep. 30, 2023
Restructuring and Related Activities [Abstract]
Curtailment of Operations - Hawesville	Curtailment of Operations - HawesvilleIn August 2022, we fully curtailed production at the Hawesville 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.For the three and nine months ended September 30, 2023, we incurred curtailment charges of approximately $2.0 million and $13.4 million, including $0.0 million and $9.0 million related to excess capacity charges, respectively. These charges were partially offset by income related to scrap and materials sales of $0.0 million and $1.2 million for the three and nine months ended September 30, 2023. Comparatively, for the three and nine months ended September 30, 2022 we recognized $4.5 million and $12.6 million, respectively, of expenses related to accrued 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, net totaling $8.0 million for the three and nine months ended September 30, 2022. See Note 14. Components of Net Periodic Benefit Cost for additional information.