CENTURY ALUMINUM CO, 10-K filed on 3/3/2025
Annual Report
v3.25.0.1
Cover Page - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Feb. 27, 2025
Jun. 30, 2024
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2024    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-34474    
Entity Registrant Name CENTURY ALUMINUM COMPANY    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 13-3070826    
Entity Address, Address Line One One South Wacker Drive    
Entity Address, Postal Zip Code 60606    
Entity Address, Address Line Two Suite 1000    
Entity Address, City or Town Chicago    
Entity Address, State or Province IL    
City Area Code 312    
Local Phone Number 696-3101    
Title of 12(b) Security Common Stock, $0.01 par value per share    
Trading Symbol CENX    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 877
Entity Common Stock, Shares Outstanding   92,293,344  
Documents Incorporated by Reference
All or a portion of Items 10 through 14 in Part III of this Form 10-K are incorporated by reference to the Registrant’s definitive proxy statement on Schedule 14A for its 2025 Annual Meeting of Stockholders, which will be filed within 120 days after the close of the fiscal year covered by this report on Form 10-K, or if the Registrant’s Schedule 14A is not filed within such period, will be included in an amendment to this Report on Form 10-K which will be filed within such 120 day period.
    
Entity Central Index Key 0000949157    
Document Fiscal Year Focus 2024    
Document Fiscal Period Focus FY    
Amendment Flag false    
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Audit Information
 12 Months Ended
Dec. 31, 2024
Audit Information [Abstract]  
Auditor Name Deloitte & Touche LLP
Auditor Location Chicago, Illinois
Auditor Firm ID 34
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CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)
shares in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
NET SALES:      
Total net sales $ 2,220.3 $ 2,185.4 $ 2,777.3
Costs of goods sold [1] 2,035.3 2,093.5 2,730.6
Gross profit 185.0 91.9 46.7
Selling, general and administrative expenses 56.8 44.3 37.5
Asset impairment 0.0 0.0 159.4
Other operating expense - net 6.8 15.8 0.0
Operating income (loss) 121.4 31.8 (150.2)
Interest income 2.1 2.0 0.5
Net gain (loss) on forward and derivative contracts - nonaffiliates 2.0 61.8 197.2
Bargain purchase gain 245.9 0.0 0.0
Other income (loss) - net (4.5) (3.3) 15.3
Income (loss) before income taxes 323.8 (66.8) 33.4
Income tax benefit (expense) (3.2) 14.6 (47.4)
Income (loss) before equity in earnings of joint ventures 320.6 (52.2) (14.0)
Equity in losses of joint ventures 0.1 (0.1) (0.1)
Net Income (loss) 320.7 (52.3) (14.1)
Net loss attributable to noncontrolling interests (16.1) (9.2) 0.0
Net income (loss) attributable to Century stockholders 336.8 (43.1) (14.1)
Less: net income allocated to participating securities 17.9 0.0 0.0
Net income (loss) allocated to common stockholders $ 318.9 $ (43.1) $ (14.1)
INCOME (LOSS) ATTRIBUTABLE TO CENTURY STOCKHOLDERS PER COMMON SHARE:      
Basic (in dollars per share) $ 3.44 $ (0.47) $ (0.15)
Diluted (in dollars per share) $ 3.27 $ (0.47) $ (0.15)
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:      
Basic (in shares) 92.8 92.4 91.4
Diluted (in shares) 98.4 92.4 91.4
Related Party      
NET SALES:      
Total net sales $ 1,312.1 $ 1,612.1 $ 1,671.1
Costs of goods sold 277.9 181.4 284.7
Interest expense (6.7) (1.8) 0.0
Net gain (loss) on forward and derivative contracts - nonaffiliates (0.5) 0.6 (13.3)
Nonrelated Party      
NET SALES:      
Total net sales 908.2 573.3 1,106.2
Interest expense (36.4) (33.7) (29.3)
Net gain (loss) on forward and derivative contracts - nonaffiliates $ 2.5 $ (62.4) $ 210.4
[1]
(1) Including purchases from related party of $277.9 million, $181.4 million and $284.7 million for the years ended December 31, 2024, 2023 and 2022, respectively.
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CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Costs of goods sold [1] $ 2,035.3 $ 2,093.5 $ 2,730.6
Related Party      
Costs of goods sold $ 277.9 $ 181.4 $ 284.7
[1]
(1) Including purchases from related party of $277.9 million, $181.4 million and $284.7 million for the years ended December 31, 2024, 2023 and 2022, respectively.
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CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Comprehensive income (loss):      
Net income (loss) $ 320.7 $ (52.3) $ (14.1)
Other comprehensive (loss) before income tax effect:      
Net loss on foreign currency cash flow hedges reclassified as income (0.2) (0.1) (0.2)
Defined benefit plans and other postretirement benefits:      
Net loss arising during the period (11.9) (10.1) (5.9)
OPEB curtailment gain, net 0.0 0.0 (8.9)
Amortization of prior service benefit during the period 0.2 0.1 (1.2)
Amortization of net loss during the period 6.5 6.2 4.8
Other comprehensive (loss) before income tax effect (5.4) (3.9) (11.4)
Income tax effect 0.0 0.0 (0.3)
Other comprehensive (loss) (5.4) (3.9) (11.7)
Comprehensive income (loss) 315.3 (56.2) (25.8)
Comprehensive loss attributable to noncontrolling interests (16.1) (9.2) 0.0
Comprehensive income (loss) attributable to Century stockholders $ 331.4 $ (47.0) $ (25.8)
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CONSOLIDATED BALANCE SHEETS - USD ($)
Dec. 31, 2024
Dec. 31, 2023
ASSETS    
Cash and cash equivalents $ 32,900,000 $ 88,800,000
Restricted cash 2,800,000 1,500,000
Accounts receivable - net 75,800,000 53,700,000
Non-trade receivables 13,200,000 36,200,000
Manufacturing credit receivable 81,500,000 59,300,000
Inventories 539,000,000.0 477,000,000.0
Derivative assets 4,200,000 2,900,000
Prepaid and other current assets 28,300,000 27,500,000
Total current assets 802,800,000 767,100,000
Property, plant and equipment - net 978,300,000 1,004,200,000
Manufacturing credit receivable - less current portion 70,400,000 0
Other assets 87,900,000 75,200,000
TOTAL 1,939,400,000 1,846,500,000
LIABILITIES:    
Accounts payable, trade 187,300,000 249,500,000
Accrued compensation and benefits 49,800,000 38,100,000
Accrued and other current liabilities 42,000,000.0 50,900,000
Derivative liabilities 4,400,000 1,400,000
Deferred credit - preliminary bargain purchase gain 0 273,400,000
Total current liabilities 463,700,000 763,000,000.0
Accrued benefits costs - less current portion 130,400,000 120,300,000
Other liabilities 92,600,000 66,300,000
Deferred taxes 71,200,000 72,400,000
Asset retirement obligations - less current portion 61,500,000 49,500,000
Total noncurrent liabilities 813,000,000.0 739,400,000
COMMITMENTS AND CONTINGENCIES (NOTE 17)
SHAREHOLDERS’ EQUITY:    
Preferred stock (Note 9) 0.0 0.0
Common stock (Note 9) 1,000,000.0 1,000,000.0
Additional paid-in capital 2,550,200,000 2,542,900,000
Treasury stock, at cost (86,300,000) (86,300,000)
Accumulated other comprehensive loss (103,300,000) (97,900,000)
Accumulated deficit (1,667,200,000) (2,004,100,000)
Total Century shareholders’ equity 694,400,000 355,600,000
Noncontrolling interest (31,700,000) (11,500,000)
Total equity 662,700,000 344,100,000
TOTAL 1,939,400,000 1,846,500,000
Related Party    
ASSETS    
Due from affiliates 25,100,000 20,200,000
LIABILITIES:    
Due to affiliates 109,300,000 101,400,000
Current maturities of long-term debt 0 10,000,000.0
Long-term debt 10,000,000.0 0
Due to affiliates - less current portion 0 0
Nonrelated Party    
LIABILITIES:    
Current maturities of long-term debt 70,900,000 38,300,000
Long-term debt $ 447,300,000 $ 430,900,000
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CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES:      
Net Income (loss) $ 320.7 $ (52.3) $ (14.1)
Adjustments to reconcile net income (loss) to net cash (used in) provided by operating activities:      
Lower of cost or NRV inventory adjustment 2.3 0.0 39.6
Unrealized (gain) loss on derivative instruments (5.0) 87.1 (201.5)
Depreciation, depletion and amortization 81.8 74.7 73.4
Change in deferred tax (benefit) provision (1.3) (30.8) 44.2
Asset impairment 0.0 0.0 159.4
Gain on sale of assets (2.3) 0.0 0.0
Bargain purchase gain (245.9) 0.0 0.0
Force majeure settlement (12.3) 0.0 0.0
Other postretirement benefits gain, net 0.0 0.0 (8.9)
Other non-cash items - net 9.1 3.4 (22.8)
Change in operating assets and liabilities, net of acquisition:      
Accounts receivable - net (18.3) 36.9 13.7
Non-trade receivables 31.5 4.1 0.0
Manufacturing credit receivable (92.6) (59.3) 0.0
Due from affiliates (4.9) (15.5) 3.6
Inventories (64.3) 25.8 (12.8)
Prepaid and other current assets 1.0 2.9 5.6
Accounts payable, trade (50.6) (19.4) (15.8)
Due to affiliates 26.1 51.7 (43.5)
Accrued and other current liabilities (1.2) 0.0 8.8
Ravenswood retiree legal settlement (2.0) (2.0) (2.0)
PBGC settlement (0.3) (4.5) (2.4)
Other - net 3.9 2.8 1.4
Net cash (used in) provided by operating activities (24.6) 105.6 25.9
CASH FLOWS FROM INVESTING ACTIVITIES:      
Purchase of property, plant and equipment (82.3) (95.0) (86.3)
Proceeds from co-tenancy assets at Jamalco JV 12.7 0.0 0.0
Proceeds from sale of property, plant and equipment 2.3 25.7 0.8
Acquisition of subsidiary net of cash acquired 0.0 11.5 0.0
Net cash used in investing activities (67.3) (57.8) (85.5)
CASH FLOWS FROM FINANCING ACTIVITIES:      
Debt issuance cost 0.0 0.0 (1.5)
Carbon credit proceeds 0.0 36.8 0.0
Carbon credit repayments (10.0) 0.0 0.0
Net cash provided by (used in) financing activities 37.3 (13.0) 74.4
CHANGE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH (54.6) 34.8 14.8
Cash, cash equivalents and restricted cash, beginning of year 90.3 55.5 40.7
Cash, cash equivalents and restricted cash, end of year 35.7 90.3 55.5
Cash paid for:      
Interest 36.0 35.2 27.0
Taxes, net of refunds 14.5 5.9 0.9
Non-cash investing activities:      
Capital expenditures 12.3 10.7 3.7
Capitalized interest 3.4 6.0 4.2
Distribution of fixed assets to NCI 17.0 0.0 0.0
U.S. and Iceland Revolving Credit Facilities      
CASH FLOWS FROM FINANCING ACTIVITIES:      
Borrowing under revolving credit or term facility 735.4 656.9 1,126.2
Repayments under revolving credit or term facility (705.1) (758.2) (1,114.8)
Casthouse Facility      
CASH FLOWS FROM FINANCING ACTIVITIES:      
Repayments under revolving credit or term facility (6.8) 0.0 0.0
Borrowings under facility agreements 25.0 55.0 50.0
Iceland Term Facility      
CASH FLOWS FROM FINANCING ACTIVITIES:      
Borrowing under revolving credit or term facility 0.0 0.0 14.5
Repayments under revolving credit or term facility (1.2) (13.5) 0.0
Vlissingen Facility Agreement      
CASH FLOWS FROM FINANCING ACTIVITIES:      
Borrowings under facility agreements $ 0.0 $ 10.0 $ 0.0
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CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($)
$ in Millions
Total
Total Century equity
Preferred stock
Common stock
Additional paid-in capital
Treasury stock, at cost
Accumulated other comprehensive loss
Accumulated deficit
Noncontrolling interest
Beginning balance (in shares) at Dec. 31, 2021     58,542            
Beginning balance at Dec. 31, 2021 $ 421.0 $ 421.0 $ 0.0 $ 1.0 $ 2,535.5 $ (86.3) $ (82.3) $ (1,946.9) $ 0.0
Beginning balance (in shares) at Dec. 31, 2021       91,231,611          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Net Income (loss) (14.1) (14.1)           (14.1)  
Other comprehensive income (loss) (11.7) (11.7)         (11.7)    
Share-based compensation (in shares)       623,582          
Share-based compensation 4.1 4.1     4.1        
Conversion of preferred stock to common stock     (4,688) 468,785          
Ending balance (in shares) at Dec. 31, 2022     53,854            
Ending balance at Dec. 31, 2022 399.3 399.3 $ 0.0 $ 1.0 2,539.6 (86.3) (94.0) (1,961.0) 0.0
Ending balance (in shares) at Dec. 31, 2022       92,323,978          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Net Income (loss) (52.3) (43.1)           (43.1) (9.2)
Other comprehensive income (loss) (3.9) (3.9)         (3.9)    
Share-based compensation (in shares)       208,867          
Share-based compensation 3.3 3.3     3.3        
Conversion of preferred stock to common stock     (1,570) 157,019          
Noncontrolling interest (2.3)               (2.3)
Ending balance (in shares) at Dec. 31, 2023     52,284            
Ending balance at Dec. 31, 2023 $ 344.1 355.6 $ 0.0 $ 1.0 2,542.9 (86.3) (97.9) (2,004.1) (11.5)
Ending balance (in shares) at Dec. 31, 2023 92,689,864     92,689,864          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Net Income (loss) $ 320.7 336.8           336.8 (16.1)
Other comprehensive income (loss) (5.4) (5.4)         (5.4)    
Share-based compensation (in shares)       341,771          
Share-based compensation 7.3 7.3     7.3        
Conversion of preferred stock to common stock     (2,569) 256,930          
Noncontrolling interest (4.0)               (4.0)
Ending balance (in shares) at Dec. 31, 2024     49,715            
Ending balance at Dec. 31, 2024 $ 662.7 $ 694.3 $ 0.0 $ 1.0 $ 2,550.2 $ (86.3) $ (103.3) $ (1,667.3) $ (31.6)
Ending balance (in shares) at Dec. 31, 2024 93,288,565     93,288,565          
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Summary of Significant Accounting Policies
 12 Months Ended
Dec. 31, 2024
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies Summary of Significant Accounting Policies
Organization — Century Aluminum Company ("Century Aluminum," "Century," the "Company", "we", "us", "our" or "ours") is a holding company, whose principal subsidiaries are Nordural ehf (together with its subsidiaries, "Nordural"), Century Aluminum Sebree LLC ("Century Sebree"), Century Aluminum of South Carolina ("CASC") and Century Kentucky, Inc. ("CAKY"). Nordural Grundartangi ehf, a subsidiary of Nordural, operates a primary aluminum smelter in Grundartangi, Iceland ("Grundartangi"). Century Sebree operates a primary aluminum smelter in Robards, Kentucky ("Sebree"). CASC operates a primary aluminum reduction smelter in Goose Creek, South Carolina ("Mt. Holly"). CAKY owns a primary aluminum smelter in Hawesville, Kentucky ("Hawesville").
In addition to our primary aluminum assets, we have a 55% joint venture interest in the Jamalco bauxite mining operation and alumina refinery in Jamaica ("Jamalco"). The Jamalco refinery supplies a substantial amount of the alumina used for production of primary aluminum at our aluminum smelter in Grundartangi, Iceland. Additionally, our subsidiary, Century Aluminum Vlissingen B.V., owns and operates a carbon anode production facility located in Vlissingen, the Netherlands ("Vlissingen"). Carbon anodes are used in the production of primary aluminum and Vlissingen currently supplies carbon anodes to Grundartangi.
As of December 31, 2024, Glencore owns 42.9% of Century’s outstanding common stock (45.8% on a fully-diluted basis assuming the conversion of all of the Series A Convertible Preferred Stock) and all of our outstanding Series A Convertible Preferred Stock. See Note 9. Shareholders' Equity for a full description of our outstanding Series A Convertible Preferred Stock. Century and Glencore enter into various transactions from time to time such as the purchase and sale of primary aluminum, purchase and sale of alumina and raw materials, tolling agreements as well as forward financial contracts and borrowing and other debt transactions. See Note 4. Related Party Transactions.
Basis of Presentation — The consolidated financial statements include the accounts of Century Aluminum Company and our subsidiaries, after elimination of all intercompany transactions and accounts.
The consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States ("U.S. GAAP"). The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Our consolidated financial statements include the consolidated results of the Jamalco joint venture, an unincorporated joint venture between General Alumina Jamaica Limited ("GAJL"), an indirect, wholly-owned subsidiary of the Company, and Clarendon Alumina Production Limited ("CAP"). CAP's interest in the joint venture is reflected as noncontrolling interest on the accompanying Consolidated Balance Sheet.
Variable Interest Entities - We evaluate arrangements and contracts with other entities to determine if they are VIEs and if we are the primary beneficiary. GAAP provides a framework for identifying VIEs and determining when a company should include the assets, liabilities, non-controlling interest, and results of activities of a VIE in its consolidated financial statements.
A VIE should be consolidated if a party with an ownership, contractual or other financial interest in the VIE (a variable interest holder) has the power to direct the VIE’s most significant activities and the obligation to absorb losses or right to receive benefits of the VIE that could be significant to the VIE. A variable interest holder that consolidates the VIE is called the primary beneficiary. Upon consolidation, the primary beneficiary generally must initially record all of the VIE’s assets, liabilities, and non-controlling interests at fair value and subsequently account for the VIE as if it were consolidated.
Our evaluation of whether our interest qualifies as the primary beneficiary of a VIE involves significant judgments, estimates and assumptions and includes a qualitative analysis of the activities that most significantly impact the VIE’s economic performance and whether the Company has the power to direct those activities, the design of the entity, the rights of the parties and the purpose of the arrangement. Jamalco is a VIE. See Note 21. Variable Interest Entity.
Revenue recognition — See Note 5. Revenue.
Cash and Cash Equivalents — Cash and cash equivalents are comprised of cash, money market funds and short-term investments having original maturities of three months or less. The carrying amount of cash equivalents approximates fair value.
Accounts Receivable and Due from Affiliates — These amounts are net of an allowance for expected losses of $0.5 million at both December 31, 2024 and 2023.
Inventories — Our inventories are stated at the lower of cost or net realizable value, using the first-in, first-out ("FIFO") and the weighted average cost method. Due to the nature of our business, our inventory values are subject to market price changes and these changes can have a significant impact on cost of goods sold and gross profit in any period. Reductions in net realizable value below cost basis at the end of a period will have an impact on our cost of goods sold as this inventory is sold in subsequent periods.
Property, Plant and Equipment — Property, plant and equipment is stated at cost. Additions and improvements are capitalized when each asset is placed into service. Asset and accumulated depreciation accounts are relieved for dispositions with resulting gains or losses included in Other income (loss) - net. Maintenance and repairs are expensed as incurred. Depreciation of plant and equipment is provided for by the straight-line method over the following estimated useful lives:
Building and improvements    10 to 45 years
Machinery and equipment    5 to 35 years
Technology and software    3 to 7 years
The Company incurs deferred costs during the development stage of a mine life cycle. Such costs include the construction of access and haul roads, detailed drilling and geological analysis to further define the grade and quality of the known bauxite, and overburden removal costs. These costs relate to sections of the related mines where the Company is currently extracting bauxite or preparing for production in the near term. These sections are outlined and planned incrementally and generally are mined over periods outlined in the Company's mine plans. The amount of geological drilling and testing necessary to determine the economic viability of the bauxite deposit being mined is such that the resources are considered to be proved mineral reserves. Mineral reserves are amortized on a units-of-production basis.
Impairment of long-lived assets — The Company reviews property, plant and equipment ("long-lived assets") for impairment whenever events or changes in circumstances, known as triggering events, indicate that the carrying amount of a long-lived asset or an asset group may not be recoverable. Management considers various factors when determining if long-lived assets should be evaluated for impairment, including a significant adverse change in the business climate or industry conditions (such as sustained decreases in commodity prices, volatility in energy costs, and the global economy), a current period operating or cash flow loss combined with a history of losses, a significant adverse change in the extent or manner in which an asset is used or a current expectation that the asset will be sold or otherwise disposed of before the end of its useful life. If a triggering event is identified, the Company determines if the long-lived asset or asset group is recoverable. Recoverability is measured by comparison of the carrying amount of a long-lived asset or asset group held and used to estimate undiscounted future net cash flows expected to be generated by the long-lived asset or asset group. Impairment evaluation and fair value is based on estimates and assumptions that take into account our business plans and a long-term investment horizon, including consideration of commodity pricing, energy costs and other global economic conditions which may have an adverse effect on recoverability. If deemed unrecoverable, an impairment loss would be recognized for the amount by which the carrying amount exceeds the estimated fair value of the long-lived asset or asset group.
Leases — We determine whether an arrangement is a lease at the inception of the arrangement based on the terms and conditions in the contract. A contract contains a lease if there is an identified asset which we have the right to control. We have made a policy election not to separate lease and non-lease components within contracts. We have also elected not to recognize the impact of short term leases in the right of use asset ("ROUA") and right of use liability ("ROUL") balances. Short term leases are leases that have a lease term less than one year and do not include a purchase option.
Income Taxes — We account for income taxes using the asset and liability method, whereby deferred income taxes reflect the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. In evaluating our ability to realize deferred tax assets, we use judgment to determine if it is more likely than not that some portion or all of a deferred tax asset will not be realized, and if a corresponding valuation allowance is required.
Defined Benefit Pension and Other Postretirement Benefits — We sponsor defined benefit pension and OPEB plans for certain of our domestic hourly and salaried employees and a supplemental executive retirement benefit plan for certain current and former executive officers. Plan assets and obligations are measured annually or more frequently if there is a re-measurement event, based on the Company’s measurement date utilizing various actuarial assumptions. We attribute the service costs for the plans over the working lives of plan participants. The effects of actual results differing from our assumptions and the effects of changing assumptions are considered actuarial gains or losses. Actuarial gains or losses are recorded in Accumulated Other Comprehensive Income (Loss).
We contribute to our defined benefit pension plans based upon actuarial and economic assumptions designed to achieve adequate funding of the projected benefit obligations and to meet the minimum funding requirements.
Postemployment Benefits — We provide certain postemployment benefits to certain former and inactive employees and their dependents during the period following employment, but before retirement. These benefits include salary continuance, supplemental unemployment and disability health care. We recognize the estimated future cost of providing postemployment benefits on an accrual basis over the active service life of the employee.
Derivatives and Hedging — As a global producer of primary aluminum, our operating results and cash flows from operations are subject to risk of fluctuations in the market prices of primary aluminum. We may from time to time enter into financial contracts to manage our exposure to such risk. Derivative instruments may consist of variable to fixed financial contracts and back-to-back fixed to floating arrangements for a portion of our sale of primary aluminum, where we receive fixed and pay floating prices from our customers and to counterparties, respectively.
From time to time, we may manage our exposure to fluctuations in the market price of power through financial instruments designed to protect our downside risk exposure. We are also exposed to foreign currency risk, and we may manage our exposure by entering into foreign currency forward contracts or option contracts for forecasted transactions and projected cash flows for foreign currencies in future periods.
Our derivatives are not designated as cash flow hedges.
Derivative and hedging instruments are recorded in due from affiliates, derivative assets, other assets, due to affiliates, derivative liabilities and derivative liabilities - less current portion in the Consolidated Balance Sheets at fair value. We value our derivative and hedging instruments using quoted market prices and other significant unobservable inputs.
We recognize changes in fair value and settlements of derivative instruments in net gain (loss) on forward and derivative contracts in the Consolidated Statements of Operations as they occur.
Unrealized gains on forward and derivative contracts are reported as part of cash flows from operations in the Consolidated Statements of Cash Flows.
Foreign Currency – We are exposed to foreign currency risk due to fluctuations in the value of the U.S. dollar as compared to the Euro and the Icelandic krona ("ISK"), and the Chinese renminbi. Grundartangi, Vlissingen and Jamalco use the U.S. dollar as their functional currency, as contracts for sales of aluminum and alumina and purchases of alumina and power are denominated in U.S. dollars. Transactions denominated in currencies other than the functional currency are recorded based on exchange rates at the time such transactions arise and any transaction gains and losses are reflected in Other income (loss) - net in the Consolidated Statements of Operations.
Financial Instruments — Receivables, certain life insurance policies, payables, borrowings under revolving credit facilities and debt related to industrial revenue bonds ("IRBs") are carried at amounts that approximate fair value.
Earnings per share — Basic earnings (loss) per share ("EPS") amounts are calculated by dividing earnings (loss) available to common stockholders by the weighted average number of common shares outstanding using the two-class method. Under the two-class method, net income is allocated between shares of common stock and other participating securities based on their participating rights. Net loss is not allocated to other participating securities if they are not obligated to share in the losses based on their contractual terms. Diluted earnings per share is calculated by dividing net income attributable to common shareholders by the weighted average number of common and dilutive common equivalent shares outstanding during the period. Common equivalent shares are not included in the denominator of the diluted loss per share calculation when inclusion of such shares would be anti-dilutive.
The dilutive effect to earnings per share is determined using the "if converted" method whereby, if the conversion of the convertible notes would be dilutive, interest expense on the outstanding notes is added back to the diluted earnings numerator and all of the potentially dilutive shares are included in the diluted common shares outstanding denominator for the computation of diluted earnings per share.
Our Series A Convertible Preferred Stock is a non-cumulative perpetual participating convertible preferred stock with no set dividend preferences. In periods where we report net losses, we do not allocate these losses to the Convertible Preferred Stock for the computation of basic or diluted EPS.
Asset Retirement Obligations — We are subject to environmental regulations which create certain legal obligations related to the normal operations of our bauxite mine and alumina refinery and our domestic primary aluminum smelter operations. Our asset retirement obligations ("AROs") consist primarily of costs associated with mine reclamation obligations, closure of bauxite residue areas, landfill closure, and the disposal of spent potliner used in the reduction cells of our domestic smelters. AROs are recorded on a discounted basis at the time the obligation is incurred (when the potliner is put in service or upon disturbance of lands to be mined) and accreted over time for the change in the present value of the liability. We capitalize the asset retirement costs by increasing the carrying amount of the related long-lived assets and depreciating these assets over their remaining useful lives.
Certain conditional asset retirement obligations ("CAROs") related to the remediation of our primary aluminum facilities for hazardous material, such as landfill materials and asbestos, have not been recorded because they have an indeterminate settlement date. CAROs are a legal obligation to perform an asset retirement activity in which the timing and/or method of settlement are conditional on a future event that may or may not be within our control.
Concentrations of Credit Risk — Financial instruments, which potentially expose us to concentrations of credit risk, consist principally of trade receivables. Our limited customer base increases our concentrations of credit risk with respect to trade receivables. We routinely assess the financial strength of our customers and collectability of our trade receivables and recognize an allowance based on our estimate of lifetime expected credit losses in accordance with the current expected credit loss ("CECL") model.
Share-Based Compensation — We measure the cost of employee services received in exchange for an award of equity instruments based on the fair value of the award on the grant date. We recognize the cost over the period during which an employee is required to provide service in exchange for the award. We issue shares to satisfy the requirements of our share-based compensation plans. At this time, we do not plan to issue treasury shares to support our share-based compensation plans, but we may in the future. We award performance units to certain officers and employees. The performance units may be settled in cash or common stock at the discretion of the Board. We have not issued any stock options since 2009.
Recent accounting pronouncements
In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, that requires disclosure of significant segment expenses that are regularly reviewed by the chief operating decision maker and included within each reported measure of segment profit or loss. The standard also requires disclosure of the composition of other segment items included in the measure of segment profit or loss that are not separately disclosed. The new standard is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We adopted this accounting standard for our fiscal year beginning January 1, 2024, retrospectively. Therefore, prior periods have been updated to conform with the current period presentation. See Note 19. Business Segments for our reportable segment disclosures.
In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, that requires presentation of specific categories of reconciling items, as well as reconciling items that meet a quantitative threshold, in the reconciliation between the income tax provision and the income tax provision using statutory tax rates. The standard also requires disclosure of income taxes paid disaggregated by jurisdiction with separate disclosure of income taxes paid to individual jurisdictions that meet a quantitative threshold. The amendments in this accounting standard are effective for fiscal years beginning after December 15, 2024, on a prospective basis. Early adoption and retrospective application are permitted. We do not expect the adoption of this accounting standard to have an impact on our consolidated financial statements, but will require certain additional disclosures. The Company plans to adopt this guidance on its consolidated financial statements and related disclosures for the annual period ending December 31, 2025.
In November 2024, the FASB issued ASU 2024-03, Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, that requires disclosure of the amounts of purchases of inventory, employee compensation, depreciation, and intangible asset amortization included in each relevant expense line item on the income statement. The standard also requires a qualitative description of other amounts included in each relevant expense line item on the income statement that are not separately disclosed. In addition, entities are required to disclose the nature and amount of selling expenses. The new standard is effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027. Early adoption is permitted. We do not expect any impact to the consolidated financial statements, but the standard will require certain additional disclosures in the notes to the consolidated financial statements and the Company plans to adopt this guidance for the annual period ending December 31, 2027.
v3.25.0.1
Acquisition of Jamalco
 12 Months Ended
Dec. 31, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]  
Acquisition of Jamalco Acquisition of Jamalco
On May 2, 2023, our wholly-owned subsidiary, Century Aluminum Jamaica Holdings, Inc., completed the acquisition of all the outstanding share capital of General Alumina Holdings Limited, the holder of a 55% interest in Jamalco JV ("Jamalco"), an unincorporated joint venture engaged in bauxite mining and alumina production in Jamaica. The remaining 45% interest in Jamalco is owned by Clarendon Alumina Production Limited ("CAP"), which in turn is owned by the Government of Jamaica. The purchase price for the acquisition was $1.00. The acquisition resulted in a bargain purchase gain in part due to the seller experiencing financial distress following curtailment of Jamalco's operations in the second half of 2021 due to a facility fire, with operations restarting in the second half of 2022.
The acquisition was accounted for as a business combination under the acquisition method of accounting in accordance with ASC 805 - Business Combinations, resulting in the Company recognizing the assets and liabilities at fair value with the excess over fair value of consideration transferred to the seller presented as a bargain purchase gain of $245.9 million recognized within the Consolidated Statements of Operations for the year ended December 31, 2024. During the first quarter of 2024, the Company finalized the Jamalco purchase price allocation and recognized measurement period adjustments, which primarily resulted from third-party valuation adjustments to risk premiums, reducing the value of property, plant and equipment by $29.0 million. This reduction in value of property plant and equipment resulted in a corresponding reduction to the bargain purchase gain of $29.0 million decreasing the value of the previously deferred bargain purchase gain of $273.4 million as of December 31, 2023. The Company finalized its purchase accounting as of March 31, 2024.
The following table summarizes the estimated fair value of identified assets acquired, liabilities assumed and noncontrolling interest at the date of acquisition:
Purchase price allocationAmount
Identifiable assets acquired and liabilities assumed
Cash and cash equivalents$19.4 
Restricted cash8.3 
Accounts receivable - net7.7 
Non-trade receivables40.4 
Inventories103.9 
Prepaid and other current assets4.2 
Property, plant and equipment217.2 
Other assets26.1 
Accounts payable, trade(94.6)
Accrued and other current liabilities(29.5)
Other liabilities(36.5)
Asset retirement obligations(23.9)
Total identifiable assets acquired and liabilities assumed242.7 
Less: noncontrolling interest (3.2)
Bargain purchase gain245.9 
For the twelve months ended December 31, 2023, Jamalco contributed $150.3 million to our total revenues and a loss of $41.1 million to our total earnings. In connection with the acquisition, the Company incurred approximately $1.4 million of transaction costs for the twelve months ended December 31, 2023, which are included in selling, general and administrative expenses on the Consolidated Statements of Operations.
The following unaudited pro forma financial information reflects the results of operations of the Company for the twelve months ended December 31, 2023 and 2022, respectively, as if the acquisition of Jamalco had been completed on January 1, 2022. This unaudited pro forma financial information has been prepared for informational purposes and is not necessarily indicative of the actual consolidated results of operations had the acquisition been completed on January 1, 2022, nor is the information indicative of future results of operations of the combined companies.
Year Ended December 31,
20232022
Revenue
$2,235.1 $2,831.0 
Earnings
$(45.9)$(33.1)
v3.25.0.1
Curtailment of Operations - Hawesville
 12 Months Ended
Dec. 31, 2024
Restructuring and Related Activities [Abstract]  
Curtailment of Operations - Hawesville Curtailment of Operations - Hawesville
In August 2022, we fully curtailed production at the Hawesville facility. We continue to explore all options related to the Hawesville facility.
For the year ended December 31, 2024, we incurred curtailment charges of $6.8 million, These charges were partially offset by income related to scrap and materials sales of $0.5 million. Comparatively, for the year ended December 31, 2023, we incurred curtailment charges of $16.6 million, including $9.0 million related to demand capacity charges for power. These charges were partially offset by income related to scrap and material sales of $1.7 million.
v3.25.0.1
Related Party Transactions
 12 Months Ended
Dec. 31, 2024
Related Party Transactions [Abstract]  
Related Party Transactions Related Party Transactions
The significant related party transactions occurring during the years ended December 31, 2024, 2023 and 2022 are described below. All of our related party transactions are subject to the Company's Related Party Transaction Policy and are required to be made on an arm's length basis and on terms that are fair and reasonable to the Company and substantially the same as would apply if the other party was not a related party. We believe all of our transactions with related parties are at prices that approximate market.
Glencore ownership
As of December 31, 2024, Glencore plc and its affiliates (together "Glencore") beneficially owned 42.9% of Century’s outstanding common stock (45.8% on a fully-diluted basis assuming the conversion of all of the Series A Convertible Preferred Stock) and all of our outstanding Series A Convertible Preferred Stock. See Note 9. Shareholders' Equity for a full description of our outstanding Series A Convertible Preferred Stock. Century and Glencore enter into various transactions from time to time such as the purchase and sale of primary aluminum, purchase and sale of alumina and other raw materials, tolling agreements as well as forward financial contracts and borrowing and other debt transactions.
Sales to Glencore
For the years ended December 31, 2024, 2023 and 2022 we derived approximately 59.1%, 73.8% and 60.2% of our consolidated sales from Glencore, respectively.
Glencore purchases aluminum produced at our U.S. smelters at prices based on the LME plus the Midwest regional delivery premium plus any additional market-based product premiums. Glencore purchases aluminum produced at our Grundartangi, Iceland smelter at prices based on the LME plus the European Duty Paid premium plus any additional market-based product premiums.
We have entered into agreements with Glencore pursuant to which we sell certain amounts of alumina at market-based prices. For the years ended December 31, 2024, 2023 and 2022 we recorded $191.3 million, $191.7 million, and $24.9 million of revenue related to alumina sales to Glencore, respectively.
Purchases from Glencore
We purchase a portion of our alumina and certain other raw material requirements from Glencore. Alumina purchases from Glencore during 2024 were priced based on published alumina and aluminum indices as well as fixed prices.
Financial contracts with Glencore
We have certain financial contracts with Glencore. See Note 20. Derivatives regarding these forward financial sales contracts.
Summary
A summary of the aforementioned significant related party sales and purchases for the years ended December 31, 2024, 2023 and 2022 is as follows:
 Year Ended December 31,
 202420232022
Net sales to Glencore$1,312.1 $1,612.1 $1,671.1 
Purchases from Glencore (1)
277.9 181.4 284.7 
(1)Includes settlements of financial contract positions.
Vlissingen Credit Facility
On December 9, 2022, Vlissingen entered into a Facility Agreement with Glencore International AG which was amended and extended on October 1, 2024 (as amended, the "Vlissingen Credit Facility"). The availability period for borrowings under the Vlissingen Credit Facility was extended by two years and now ends on December 2, 2026. Pursuant to the terms of the Vlissingen Credit Facility, Vlissingen may borrow from time to time up to $90 million in one or more loans at either (i) a fixed interest rate equal to 8.75% per annum (the "Fixed rate"), or (ii) a variable interest rate equal to the 1-month SOFR rate plus 3.687 percentage points, subject to an absolute maximum level of 9.00% and an absolute minimum level of 7.00% (the "Variable Rate"). The Fixed Rate is only applicable to borrowings made on or before December 1, 2024, after which the Variable Rate shall apply to all borrowings under the Vlissingen Credit Facility. See Note 8. Debt for additional information. Borrowings under the Facility Agreement are expected to be used for general corporate and working capital purposes of Century and its subsidiaries.
Carbon Credit Repurchase Agreement
On September 28, 2023, our wholly owned subsidiary Nordural Grundartangi ehf ("Grundartangi"), entered into a structured repurchase arrangement with an affiliate of Glencore pursuant to which it sold 390,000 European Union Allowances ("Carbon Credits") at a price of €82.18 per Carbon Credit, for an aggregate amount of €32.1 million. Pursuant to the terms of the transaction, Grundartangi will repurchase the same number of Carbon Credits at a price of €83.72 per Carbon Credit, for an aggregate amount of €32.7 million. On December 18, 2023, the repurchase arrangement was amended to extend the repurchase window and increase the repurchase price to €85.13 per Carbon Credit, for an aggregate amount of €33.2 million. Also on December 18, 2023, Grundartangi sold an additional 40,000 Carbon Credits at a price of €69.30 per Carbon Credit and will repurchase the same number of Carbon Credits at a price of €70.71 per Carbon Credit for an aggregate amount of €2.8 million.
In March 2024, the Amended Agreement was amended to extend the repurchase window from March 25, 2024 to August 30, 2024 and the repurchase price was revised to €87.01 per Carbon Credit, for an aggregate amount of €33.9 million. In addition, the Second Agreement was amended to extend the repurchase window from March 25, 2024 to August 30, 2024 and revised the repurchase price to €72.59 per Carbon Credit, for an aggregate amount of €2.9 million.
In August 2024, the Amended Agreement was amended to extend the repurchase window from August 30, 2024 to December 27, 2024 for 370,700 Carbon Credits. The repurchase price was revised to €71.20 per Carbon Credit, for an aggregate amount of €26.4 million. In addition, 59,300 Carbon Credits were settled on August 30, 2024 for an aggregate amount of €11.1 million.
In December 2024, the Amended Agreement was amended to extend the repurchase window from December 27, 2024 to August 22, 2025 for 370,700 Carbon Credits. The repurchase price was revised to €69.16 per Carbon Credit, for an aggregate amount of €25.6 million.
Due to the repurchase element of these transactions, the Company retains substantially all of the remaining benefits of the assets and has accounted for the transaction as a financing arrangement in accordance with Topic 606, Revenue from Contracts with Customers ("ASC 606").
v3.25.0.1
Revenue
 12 Months Ended
Dec. 31, 2024
Revenue from Contract with Customer [Abstract]  
Revenue Revenue
We disaggregate our revenue by geographical region as follows:
Year ended December 31,
Net Sales202420232022
United States$1,427.0 $1,358.6 $1,737.2 
Iceland793.3 826.8 1,040.1 
Total$2,220.3 $2,185.4 $2,777.3 
The table below shows the amount of net sales to external customers for each of the Company's product categories which accounted for 10% or more of consolidated net sales in either period for the years ended December 31, 2024, 2023 and 2022.
Year ended December 31,
Net Sales202420232022
Aluminum$1,882.1 $1,972.6 $2,750.3 
Alumina338.2 212.8 27.0 
Total$2,220.3 $2,185.4 $2,777.3 
We enter into contracts to sell mainly primary aluminum to our customers. Revenue is recognized when our performance obligations with our customers are satisfied. Our obligations under the contracts are satisfied when we transfer control of our primary aluminum to our customers which is generally upon shipment or delivery to customer directed locations. The amount of consideration we receive, thus the revenue we recognize, is a function of volume delivered, market price of primary aluminum, which is based on the LME, plus regional premiums and any value-added product premiums or alumina which is based on the alumina pricing index, plus Atlantic differential.
The payment terms and conditions in our contracts vary and are not significant to our revenue. We complete an appropriate credit evaluation for each customer at contract inception. Customer payments are due in arrears and are recognized as accounts receivable - net and due from affiliates in our Consolidated Balance Sheets.
In connection with our sales agreements with certain customers, including Glencore, we invoice the customer prior to physical shipment of goods for a majority of production generated from each of our U.S. domestic smelters. For those sales, revenue is recognized only when the customer has specifically requested such treatment and has made a commitment to purchase the product. The goods must be complete, ready for shipment and separated from other inventory with control over the goods passing to the customer. We must retain no further performance obligations.
Contract liabilities are recorded when cash payments are received or due in advance of performance. As of December 31, 2024, and 2023, amounts recorded in Due to affiliates were $41.2 million and $30.6 million, respectively.
v3.25.0.1
Leases
 12 Months Ended
Dec. 31, 2024
Leases [Abstract]  
Leases Leases
We are a lessee in various agreements for the lease of office space, land, automobiles, and mobile equipment. All of our leases are considered operating leases. The terms of our leases vary, including the lease term and the ability to renew or extend certain leases. As part of determining the lease term and potential extensions for purposes of calculating the ROUA and ROUL, we consider our historical practices related to renewal of certain leases. The weighted average remaining lease term for our
operating leases was 10.1 years as of December 31, 2024 and 11.8 years as of December 31, 2023. Certain lease payment amounts are variable in nature and change periodically based on the local market consumer price index.
We use our incremental borrowing rate as the basis for the discount rate used to calculate the ROUA and ROUL, respectively, for our operating leases. The incremental borrowing rate is determined on a lease-by-lease basis and is based on the rate of interest that we would have to pay to borrow on a collateralized basis over a similar term for an amount equal to our lease payments. We consider the most likely financing options available for each lease based on the leased asset, legal entity party to the lease, economic environment in which the lease is denominated, the market conditions relative to the leased asset and our historical practices of obtaining financing for similar types of costs. The weighted average discount rate for our operating leases was 7.5% as of December 31, 2024 and 7.3% as of December 31, 2023.
Our ROUA and ROUL balances for the years ended December 31, 2024 and December 31, 2023 were as follows (in millions):
December 31,
20242023
ROUA(1)
$21.0 $24.7 
ROUL - current(2)
$3.0 $2.3 
ROUL - non-current(3)
18.7 21.9 
Total ROUL$21.7 $24.2 
(1)ROUA was recorded as part of Other Assets within Non-current assets at December 31, 2024 and 2023.
(2)ROUL - current was recorded as part of Accrued and other current liabilities within Current liabilities at December 31, 2024 and 2023.
(3)ROUL - non-current was recorded as part of Other liabilities within Non-current liabilities at December 31, 2024 and 2023.
The undiscounted maturities of our operating lease liability balances as of December 31, 2024 are as follows (in millions):
Year
2025$3.9 
20263.3 
20272.8 
20282.8 
20292.7 
Thereafter16.2 
Total 31.7 
Less: Interest(10.0)
ROUL$21.7 
During 2024 and 2023, we entered into new lease obligations, which resulted in $2.0 million and $3.2 million of additional right of use assets, respectively. During 2023, we acquired $2.4 million of right of use assets related to lease obligations assumed from the Jamalco acquisition.
Total operating expense includes the following (in millions):
December 31,
20242023
Operating leases expense$5.3 $4.9 
Short term lease expense3.2 0.6 
Total(1)
$8.5 $5.5 
(1)Total lease expense is included in cost of goods sold and selling, general, and administrative expenses on the Consolidated Statements of Operations.
We had cash outflows of $5.0 million and $4.6 million for amounts included in the ROUL balance at the beginning of the year related to our operating leases for the years ended December 31, 2024 and December 31, 2023, respectively.
v3.25.0.1
Fair Value Measurements
 12 Months Ended
Dec. 31, 2024
Fair Value Disclosures [Abstract]  
Fair Value Measurements Fair Value Measurements
We measure certain of our assets and liabilities at fair value. Fair value represents the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.
In general, reporting entities should apply valuation techniques to measure fair value that maximize the use of observable inputs and minimize the use of unobservable inputs. Observable inputs are developed using market data and reflect assumptions that market participants would use when pricing the asset or liability. Unobservable inputs are developed using the best information available about the assumptions and estimates that market participants would use when pricing the asset or liability.
The fair value hierarchy provides transparency regarding the inputs we use to measure fair value. We categorize each fair value measurement in its entirety into the following three levels, based on the lowest level input that is significant to the entire measurement:
•Level 1 Inputs – quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date.
•Level 2 Inputs – inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.
•Level 3 Inputs – unobservable inputs for the asset or liability.
Recurring Fair Value Measurements
As of December 31, 2024
Level 1Level 2Level 3Total
ASSETS:    
Cash equivalents$7.9 $— $— $7.9 
Trust assets (1)
0.3— — 0.3
Derivative instruments— 4.5 — 4.5 
TOTAL$8.2 $4.5 $— $12.7 
LIABILITIES:    
Derivative instruments— 4.4 — 4.4 
TOTAL$— $4.4 $— $4.4 
Recurring Fair Value Measurements
As of December 31, 2023
Level 1Level 2Level 3Total
ASSETS:    
Cash equivalents$16.8 $— $— $16.8 
Trust assets (1)
0.2— — 0.2 
Derivative instruments— 2.9 — 2.9 
TOTAL$17.0 $2.9 $— $19.9 
LIABILITIES:    
Derivative instruments— 7.9 — 7.9 
TOTAL$— $7.9 $— $7.9 
(1)Trust assets are currently invested in money market funds. These trust assets are held to fund the non-qualified supplemental executive pension benefit obligations for certain of our officers.
The following section describes the valuation techniques and inputs used for fair value measurements categorized within Level 2 of the fair value hierarchy:
Level 2 Fair Value Measurements:
Asset / LiabilityValuation TechniquesInputs
LME forward financial sales contractsDiscounted cash flowsQuoted LME forward market, Secured Overnight Financing Rate ("SOFR") discount rate
Midwest Premium ("MWP") forward financial sales contractsDiscounted cash flowsQuoted MWP forward market, SOFR discount rate
Fixed for floating swapsDiscounted cash flowsQuoted LME forward market, quoted MWP forward market
Indiana Hub power price swapsDiscounted cash flowsQuoted Indiana Hub forward market, SOFR discount rate
FX swaps Discounted cash flowsEuro/USD forward exchange rate
Casthouse currency hedgesDiscounted cash flowsEuro/USD forward exchange rate; ISK/USD forward exchange rate
Heavy Fuel Oil ("HFO") price swapsDiscounted cash flowsQuoted HFO forward market
When valuing Level 3 assets and liabilities, we use certain significant unobservable inputs. Management incorporates various inputs and assumptions including forward commodity prices, commodity price volatility and macroeconomic conditions, including interest rates and discount rates. Our estimates of significant unobservable inputs are ultimately based on our estimates of risks that market participants would consider when valuing our assets and liabilities.
As of the years ending December 31, 2024, and December 31, 2023, there were no Level 3 assets and liabilities.
The following table presents the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis.
For the twelve months ended December 31, 2023 and 2024Level 3 AssetsLevel 3 Liabilities
LME forward financial sales contractsLME forward financial sales contracts
Balance as of January 1, 2023$1.8 $(4.6)
Transfers out of Level 3 (1)
(1.8)4.6 
Balance as of December 31, 2023$— $— 
Transactions during 2024$— $— 
Balance as of December 31, 2024$— $— 
Change in unrealized gains (losses) 2023 (2)
$— $— 
Change in unrealized gains (losses) 2024 (2)
$— $— 
(1)Transfer out of Level 3 due to period of time remaining in derivative contract.
(2)Gains and losses are presented in the Consolidated Statements of Operations within the line item "Net gain (loss) on forward and derivative contracts."
v3.25.0.1
Debt
 12 Months Ended
Dec. 31, 2024
Debt Disclosure [Abstract]  
Debt Debt
 December 31,
 20242023
Debt classified as current liabilities:  
Hancock County industrial revenue bonds ("IRBs") due April 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) (1)
$7.8 $7.8 
U.S. Revolving Credit Facility (2)
20.0 23.7 
Iceland Revolving Credit Facility (3)
34.0 — 
Grundartangi Casthouse Facility (4)
9.0 5.5 
Iceland Term Facility
— 1.3 
Vlissingen Facility Agreement (5)
— 10.0 
Debt classified as non-current liabilities:  
Grundartangi casthouse facility, net of financing fees of $0.0 million at December 31, 2024 (4)
114.2 98.8 
Vlissingen Facility Agreement (5)
10.0 — 
7.5% senior secured notes due April 1, 2028, net of financing fees of $1.9 million at December 31, 2024, interest payable semiannually
248.1 247.4 
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.2 million at December 31, 2024, interest payable semiannually
85.1 84.7 
Total$528.2 $479.2 
(1)The IRBs are classified as current liabilities because they are remarketed weekly and could be required to be repaid upon demand if there is a failed remarketing. The interest rate at December 31, 2024 was 3.75%.
(2)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at December 31, 2024 was 8.00%.
(3)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at December 31, 2024 was 7.84%.
(4)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at December 31, 2024 was 8.06%.
(5)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at December 31, 2024 was 7.99%
7.5% Senior Secured Notes due 2028
General. On April 14, 2021, we issued $250.0 million in aggregate principal amount of 7.5% senior secured notes due 2028 (the "2028 Notes"). We received proceeds of $245.2 million, after payment of certain financing fees and related expenses.
Interest Rate. The 2028 Notes bear interest semi-annually in arrears on April 1 and October 1 of each year, beginning on October 1, 2021, at a rate of 7.5% per annum in cash.
Maturity. The 2028 Notes mature on April 1, 2028.
Seniority. The 2028 Notes are senior secured obligations of Century, ranking equally in right of payment with all existing and future senior indebtedness of Century, but effectively senior to unsecured debt to the extent of the value of collateral.
Guaranty. Our obligations under the 2028 Notes are guaranteed by all of our existing and future domestic restricted subsidiaries (the “Guarantor Subsidiaries”), except for foreign owned holding companies, any domestic restricted subsidiary that owns no assets other than equity interests or other investments in foreign subsidiaries and certain immaterial subsidiaries, which guaranty shall in each case be a senior secured obligation of such Guarantor Subsidiaries, ranking equally in right of payment with all existing and future senior indebtedness of such Guarantor Subsidiaries but effectively senior to unsecured debt to the extent of the value of collateral.
Collateral. Our obligations under the 2028 Notes and the Guarantor Subsidiaries' obligations under the guarantees are secured by a pledge of and lien on (subject to certain exceptions):
(i) all of our and the Guarantor Subsidiaries' property, plant and equipment (other than certain excluded property);
(ii) all equity interests in subsidiaries directly owned by Century or any Guarantor Subsidiaries; and
(iii) proceeds of the foregoing.
Under certain circumstances, the indenture and the security documents governing the 2028 Notes will permit us and the Guarantors to incur additional debt that also may be secured by liens on the collateral that are equal to or have priority over the liens securing the 2028 Notes. The collateral agent for the 2028 Notes will agree with the collateral agent for the other debt holders and us under such circumstances to enter into an intercreditor agreement that will cause the liens securing the 2028 Notes to be contractually subordinated to the liens securing such additional debt.
Redemption Rights. Prior to April 1, 2024, we may redeem the 2028 Notes, in whole or in part, at a redemption price equal to 100.00% of the principal amount plus a make-whole premium and accrued and unpaid interest, and if redeemed during the twelve-month period beginning on April 1 of the years indicated below, at the following redemption prices plus accrued and unpaid interest:
YearPercentage
2024103.750%
2025101.875%
2026 and Thereafter100.000%
Upon a change of control (as defined in the indenture governing the 2028 Notes), we will be required to make an offer to purchase the 2028 Notes at a purchase price equal to 101% of the outstanding principal amount of the 2028 Notes on the date of the purchase, plus accrued and unpaid interest to, but not including, the date of purchase.
Covenants. The indenture governing the 2028 Notes contains customary covenants which may limit our ability, and the ability of certain of our subsidiaries, to: (i) incur additional debt; (ii) incur additional liens; (iii) pay dividends or make distributions in respect of capital stock; (iv) purchase or redeem capital stock; (v) make investments or certain other restricted payments; (vi) sell assets; (vii) issue or sell stock of certain subsidiaries; (viii) enter into transactions with shareholders or affiliates; and (ix) effect a consolidation or merger.
Fair Value. As of December 31, 2024, the total estimated fair value of the 2028 Notes was $253.1 million. Although we use quoted market prices for identical debt instruments, the markets on which they trade are not considered to be active and are therefore considered Level 2 fair value measurements.
2.75% Convertible Notes due 2028
General. On April 9, 2021, we completed a private offering of $86.3 million aggregate principal amount of convertible senior notes due 2028 (the "Convertible Notes"). The Convertible Notes were issued at a price of 100% of their aggregate principal amount. We received proceeds of $83.7 million, after payment of certain financing fees and related expenses.
The initial conversion rate for the Convertible Notes is 53.3547 shares of the Company's common stock per $1,000 principal amount of Convertible Notes, which is equivalent to an initial conversion price of approximately $18.74 per share of the Company's common stock. The conversion rate and conversion price are subject to customary adjustments under certain circumstances in accordance with the terms of the indenture.
Interest Rate. The Convertible Notes will bear interest semi-annually in arrears on May 1 and November 1 of each year, beginning on November 1, 2021, at a rate of 2.75% per annum in cash.
Maturity. The Convertible Notes will mature on May 1, 2028, unless earlier converted, repurchased, or redeemed.
Seniority. The Convertible Notes are the Company’s senior unsecured obligations and rank senior in right of payment to any of the Company’s indebtedness that is expressly subordinated in right of payment to the Convertible Notes; equal in right of payment to any of the Company’s unsecured indebtedness that is not so subordinated; effectively junior in right of payment to any of the Company’s senior secured indebtedness to the extent of the value of the assets securing such indebtedness; and structurally junior to all indebtedness and other liabilities (including trade payables) of the Company’s subsidiaries.
Redemption rights. We may not redeem the Convertible Notes prior to May 6, 2025. On or after May 6, 2025, we may redeem for cash all or part of the Convertible Notes at our option if the last reported sale price of our common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading-day period (including the last trading day of such period) ending on and including the trading day immediately preceding the date on which we provide notice of redemption, at a redemption price equal to 100% of the principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest.
Upon conversion, we may satisfy our conversion obligation by paying or delivering, as applicable, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, based on the applicable conversion rate. In addition, if certain corporate events that constitute a make-whole fundamental change (as defined in the indenture) occur, then the conversion rate will, in certain circumstances, be increased for a specified period of time. Additionally, in the event of a corporate event constituting a fundamental change (as defined in the indenture), holders of the Convertible Notes may require us to repurchase all or a portion of their Convertible Notes at a repurchase price equal to 100% of the principal amount of the Convertible Notes being repurchased, plus accrued and unpaid interest to, but excluding, the date of the fundamental change repurchase.
As of December 31, 2024, the if-converted value of the Convertible Notes did not exceed the outstanding principal amount.
Fair Value. As of December 31, 2024, the total estimated fair value of the Convertible Notes was $102.6 million. Although we use quoted market prices for identical debt instruments, the markets on which they trade are not considered to be active and are therefore considered Level 2 fair value measurements.
U.S. Revolving Credit Facility
General. We and certain of our direct and indirect domestic subsidiaries (the "Borrowers") have a senior secured revolving credit facility with a syndicate of lenders (the "U.S. revolving credit facility"). On June 14, 2022 we amended our U.S. revolving credit facility, increasing our borrowing capacity to $250.0 million, including up to $150.0 million under a letter of credit sub-facility. The U.S. revolving credit facility matures on June 14, 2027.
Any letters of credit issued and outstanding under the U.S. revolving credit facility reduce our borrowing availability on a dollar-for-dollar basis. At December 31, 2024, there were $20.0 million outstanding borrowings and $63.7 million of outstanding letters of credit issued under our U.S. revolving credit facility. Principal payments, if any, are due upon maturity of the U.S. revolving credit facility and may be prepaid without penalty.
Status of our U.S. revolving credit facility:
December 31, 2024
Credit facility maximum amount$250.0 
Borrowing availability149.3 
Outstanding letters of credit issued63.7 
Outstanding borrowings20.0 
Borrowing availability, net of outstanding letters of credit and borrowings65.6 
Borrowing Base. The availability of funds under the U.S. revolving credit facility is limited by a specified borrowing base consisting of the Borrower's accounts receivable and inventory which meet the eligibility criteria.
Guaranty. The Borrowers' obligations under the U.S. revolving credit facility are guaranteed by certain of our domestic subsidiaries and secured by a continuing lien upon and a security interest in all of the Borrowers' accounts receivable, inventory and certain bank accounts. Each Borrower is liable for any and all obligations under the U.S. revolving credit facility on a joint and several basis.
Interest Rates and Fees. Any amounts outstanding under the U.S. revolving credit facility will bear interest at our option of either the secured overnight financing rate ("SOFR") or a base rate, plus, in each case, an applicable interest margin. The applicable interest margin is determined based on the average daily availability for the immediately preceding quarter. In addition, we pay an unused line fee on undrawn amounts, less the amount of our letters of credit exposure. For standby letters of credit, we are required to pay a fee on the face amount of such letters of credit that varies depending on whether the letter of credit exposure is cash collateralized.
Prepayments. We can make prepayments of amounts outstanding under the U.S. revolving credit facility, in whole or in part, without premium or penalty, subject to standard breakage costs, if applicable. We may be required to apply the proceeds from sales of collateral accounts, other than sales of inventory in the ordinary course of business, to repay amounts outstanding under the revolving credit facility and correspondingly reduce the commitments there under.
Covenants. The U.S. revolving credit facility contains customary covenants, including restrictions on mergers and acquisitions, indebtedness, affiliate transactions, liens, dividends and distributions, dispositions of collateral, investments, and prepayments of indebtedness, as well as a covenant that requires the Borrowers to maintain certain minimum liquidity or availability requirements.
Events of Default. The U.S. revolving credit facility also includes customary events of default, including nonpayment, misrepresentation, breach of covenant, bankruptcy, change of ownership, certain judgments and certain cross defaults. Upon the occurrence of an event of default, commitments under the U.S. revolving credit facility may be terminated and amounts outstanding may be accelerated and declared immediately due and payable.
Iceland Revolving Credit Facility
General. Our wholly-owned subsidiary, Nordural Grundartangi ehf ("Grundartangi"), entered into a revolving credit facility agreement with Landsbankinn hf., dated November 2013, as amended (the "Iceland revolving credit facility") which originally provided for borrowings of up to $50.0 million in the aggregate. On February 4, 2022, we amended the Iceland revolving credit facility and increased the facility amount to $80.0 million in the aggregate. On September 28, 2022, we further amended the Iceland revolving credit facility and increased the facility amount to $100.0 million in aggregate. Under the terms of the Iceland revolving credit facility, when Grundartangi borrows funds it will designate a repayment date, which may be any date prior to the maturity of the Iceland revolving credit facility. At December 31, 2024, there was $34.0 million in outstanding borrowings under our Iceland revolving credit facility. The Iceland revolving credit facility has a term through December 2026.
Status of our Iceland revolving credit facility:
December 31, 2024
Credit facility maximum amount$100.0 
Borrowing availability100.0 
Outstanding letters of credit issued— 
Outstanding borrowings34.0 
Borrowing availability, net of outstanding letters of credit and borrowings66.0 
Borrowing Base. The availability of funds under the Iceland revolving credit facility is limited by a specified borrowing base consisting of inventory and accounts receivable of Grundartangi.
Security. Grundartangi's obligations under the Iceland revolving credit facility are secured by a general bond under which Grundartangi's inventory and accounts receivable are pledged to secure full payment of the loan.
Interest Rates and Fees. Any amounts outstanding under the Iceland revolving credit facility will bear interest at SOFR plus a margin per annum.
Prepayments. Any outstanding borrowings may be prepaid without penalty or premium in whole or in part.
Covenants. The Iceland revolving credit facility contains customary covenants, including restrictions on mergers and acquisitions, dispositions of assets, compliance with permits, laws and payment of taxes, as well as a covenant that requires Grundartangi to maintain a certain minimum equity ratio.
Events of Default. The Iceland revolving credit facility also includes customary events of default, including nonpayment, loss of license, cessation of operations, unlawfulness, breach of covenant, bankruptcy, change of ownership, certain judgments and certain cross defaults. Upon the occurrence of an event of default, commitments under the Iceland revolving credit facility may be terminated and amounts outstanding may be accelerated and declared immediately due and payable.
Grundartangi Casthouse Facility
On November 2, 2021, in connection with the casthouse project at Grundartangi, we entered into an eight-year Term Facility Agreement with Arion Bank hf, to provide for borrowings up to $130.0 million (the "Casthouse Facility"). Under the Casthouse Facility, repayments of principal amounts will be made in equal quarterly installments equal to 1.739% of the principal amount, the first payment occurring in July 2024, with the remaining 60% of the principal amount to be paid no later than the termination date in December 2029. As of December 31, 2024, there were $123.2 million in outstanding borrowings under the Casthouse Facility.
Security. Grundartangi's obligations under the Casthouse Facility are secured by a general bond on an aggregate of $430.0 million in assets and rights related to Grundartangi.
Interest Rates and Fees. The interest rate shall be at a base rate plus the applicable margin as set forth in the agreement. Grundartangi shall pay an arrangement fee equal to 0.78% of the total facility amount, 50% of which was paid upfront and 50% to be paid at the end of the availability period, and shall pay a commitment fee of 0.38% per annum on undrawn commitments, payable quarterly at the same time as interest payments are due and payable.
Prepayments. We can make prepayments of amounts outstanding under the Casthouse Facility, in whole or in part, without premium or penalty, together with accrued interest on the amount prepaid and subject to standard breakage costs, if applicable.
Covenants. The Casthouse Facility contains customary covenants, including restrictions on mergers and acquisitions, indebtedness, preservation of assets, and dispositions of assets, as well as a covenant that requires Grundartangi to maintain a certain minimum equity ratio.
Events of Default. The Casthouse Facility also includes customary events of default, including nonpayment, loss of license, cessation of operations, unlawfulness, breach of covenant, bankruptcy, change of ownership, certain judgments and certain cross defaults. Upon the occurrence of an event of default, commitments under the Casthouse facility may be terminated and amounts outstanding may be accelerated and declared immediately due and payable.
Iceland Term Facility
Our wholly-owned subsidiary, Grundartangi, entered into a Term Facility Agreement with Arion Bank hf, dated September 2022, (the "Iceland Term Facility") to provide for borrowings up to €13.6 million. Repayments of principal amounts were made in equal monthly installments, the first payment occurring in February 2023, with the remainder of the principal amount paid in January 2024. Borrowings under the Iceland Term Facility bore interest at a rate equal to 3.2% plus EUR EURIBOR 1 month as published by the European Money Markets Institute. As of December 31, 2024, the Iceland Term Facility has been repaid in full and has terminated pursuant to its terms.
Vlissingen Credit Facility
On December 9, 2022, Vlissingen entered into a Facility Agreement with Glencore International AG, which was amended and extended on October 1, 2024 (as amended, the "Vlissingen Credit Facility"). The availability period for borrowings under the Vlissingen Credit Facility was extended by two years and now ends on December 2, 2026. Pursuant to the terms of the Vlissingen Credit Facility, Vlissingen may borrow from time to time up to $90 million in one or more loans. As of December 31, 2024, there was $10.0 million in outstanding borrowings under the Vlissingen Facility Agreement.
Security. Vlissingen’s obligations under the Vlissingen Credit Facility are secured by liens on the ground lease on which Vlissingen’s facilities are located, Vlissingen’s moveable assets, financial assets, receivables and other assets, and Vlissingen’s shares.
Interest Rates and Fees. Amounts outstanding under the Vlissingen Credit Facility will bear interest at either (i) a fixed interest rate equal to 8.75% per annum (the "Fixed Rate"), or (ii) a variable interest rate equal to the 1-month SOFR rate plus 3.687 percentage points, subject to an absolute maximum level of 9.00% and an absolute minimum level of 7.00% (the "Variable Rate"). The Fixed Rate is only applicable to borrowings made on or before December 1, 2024, after which the Variable Rate shall apply to all borrowings under the Vlissingen Credit Facility.
Prepayments. Any outstanding borrowings may be prepaid without penalty or premium in whole or in part without any charge, fee premium or penalty.
Covenants. The Vlissingen Credit Facility contains customary covenants including with respect to mergers, guarantees and preservation and dispositions of assets.
Events of Default. The Vlissingen Credit Facility also includes customary events of default, including nonpayment, breach of any provision or representation under the agreement, and certain cross-default and insolvency events. Upon the occurrence of an event of default, commitments under the Vlissingen Credit Facility may be terminated and amounts outstanding may be accelerated and declared immediately due and payable.
Covenant Compliance
As of December 31, 2024, we and our subsidiaries were in compliance with all covenants or maintained availability above applicable covenant triggers.
Hancock County Industrial Revenue Bonds
As part of the purchase price for our acquisition of the Hawesville facility, we assumed IRBs which were issued in connection with the financing of certain solid waste disposal facilities constructed at the Hawesville facility. The IRBs bear interest at a variable rate not to exceed 12% per annum determined weekly based upon prevailing rates for similar bonds in the industrial revenue bond market and interest on the IRBs is paid quarterly. The IRBs are secured by a letter of credit issued under our U.S revolving credit facility and mature in April 2028.
Surety Bond Facility
As part of our normal business operations, we are required to provide surety bonds or issue letters of credit in certain states in which we do business as collateral for certain workers' compensation obligations. In June 2022, we entered into a surety bond facility with an insurance company to provide such bonds when applicable. As of December 31, 2024, we had issued surety bonds totaling $6.6 million. As we had previously guaranteed our workers' compensation obligations through issuance of letters of credit against our revolving credit facility, the surety bond issuance increases credit facility availability.
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Shareholders' Equity
 12 Months Ended
Dec. 31, 2024
Stockholders' Equity Note [Abstract]  
Shareholders' Equity Shareholders' Equity
Common Stock
As of December 31, 2024 and 2023, we had 195,000,000 shares of common stock, $0.01 cent par value, authorized under our Restated Certificate of Incorporation, of which 100,475,086 shares were issued and 93,288,565 shares were outstanding at December 31, 2024; 99,876,385 shares were issued and 92,689,864 shares were outstanding at December 31, 2023.
The rights, preferences and privileges of holders of our common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of our preferred stock which are currently outstanding, including our Series A Convertible Preferred Stock, or which we may designate and issue in the future.
Preferred Stock
As of December 31, 2024 and 2023, we had 5,000,000 shares of preferred stock, $0.01 cent par value per share, authorized under our Restated Certificate of Incorporation. Our Board of Directors may issue preferred stock in one or more series and determine for each series the dividend rights, conversion rights, voting rights, redemption rights, liquidation preferences, sinking fund terms and the number of shares constituting that series, as well as the designation thereof. Depending upon the terms of preferred stock established by our Board of Directors, any or all of the preferred stock could have preference over the common stock with respect to dividends and other distributions and upon the liquidation of Century. In addition, issuance of any shares of preferred stock with voting powers may dilute the voting power of the outstanding common stock.
Series A Convertible Preferred Stock
Shares Authorized and Outstanding. In 2008, we issued 160,000 shares of our Series A Convertible Preferred Stock. Glencore holds all of the issued and outstanding Series A Convertible Preferred Stock. At December 31, 2024 and December 31, 2023, 49,715 shares and 52,284 shares were outstanding, respectively.
The issuance of common stock under our stock incentive programs, debt exchange transactions and any stock offering that excludes Glencore participation triggers anti-dilution provisions of the preferred stock agreement and results in the automatic conversion of Series A Convertible Preferred Stock shares into shares of common stock. The conversion of preferred to common shares is 100 shares of common for each share of preferred stock. Our Series A Convertible Preferred Stock has a par value of $0.01 per share.
Dividend Rights. So long as any shares of our Series A Convertible Preferred Stock are outstanding, we may not pay or declare any dividend or make any distribution upon or in respect of our common stock or any other capital stock ranking, on a parity with or junior to, the Series A Convertible Preferred Stock in respect of dividends or liquidation preference, unless we, at the same time, declare and pay a dividend or distribution on the shares of Series A Convertible Preferred Stock (a) in an amount equal to the amount such holders would receive if they were the holders of the number of shares of our common stock into which their shares of Series A Convertible Preferred Stock are convertible as of the record date fixed for such dividend or distribution, or (b) in the case of a dividend or distribution on other capital stock ranking on a parity with or junior to the Series A Convertible Preferred Stock in such amount and in such form as (based on the determination of holders of a majority of the Series A Convertible Preferred Stock) will preserve, without dilution, the economic position of the Series A Convertible Preferred Stock relative to such other capital stock.
Voting Rights. The Series A Convertible Preferred Stock has no voting rights for the election of directors or on other matters where the shares of common stock have voting rights. However, we may not change the powers, preferences, or rights given to the Series A Convertible Preferred Stock, or authorize, create or issue any additional shares of Series A Convertible Preferred Stock without the affirmative vote of the holders of a majority of the shares of Series A Convertible Preferred Stock then outstanding (voting separately as a class).
Liquidation Rights. Upon any liquidation, dissolution, or winding-up of Century, the holders of shares of Series A Convertible Preferred Stock are entitled to receive a preferential distribution of $0.01 per share out of the assets available for distribution. In addition, upon any liquidation, dissolution or winding-up of Century, if our assets are sufficient to make any distribution to the holders of the common stock, then the holders of shares of Series A Convertible Preferred Stock are also entitled to share ratably with the holders of common stock in the distribution of Century’s assets (as though the holders of Series A Convertible Preferred Stock were holders of that number of shares of common stock into which their shares of Series A Convertible Preferred Stock are convertible). However, the amount of any such distribution will be reduced by the amount of the preferential distribution received by the holders of the Series A Convertible Preferred Stock.
Transfer Restrictions. Glencore is prohibited from transferring shares of Series A Convertible Preferred Stock to any party other than an affiliate who agrees to become bound by certain agreements associated with these shares.
Automatic Conversion. The Series A Convertible Preferred Stock automatically converts, without any further act of Century or any holders of Series A Convertible Preferred Stock, into shares of common stock, at a conversion ratio of 100 shares of common stock for each share of Series A Convertible Preferred Stock, upon the occurrence of any of the following automatic conversion events:
•If we sell or issue shares of common stock or any other stock that votes generally with our common stock, or the occurrence of any other event, including a sale, transfer or other disposition of common stock by Glencore, as a result of which the percentage of voting stock held by Glencore decreases, an amount of Series A Convertible Preferred Stock will convert to common stock to restore Glencore to its previous ownership percentage;
•If shares of Series A Convertible Preferred Stock are transferred to an entity that is not an affiliate of Glencore, such shares of Series A Convertible Preferred Stock will convert to shares of our common stock, provided that such transfers may only be made pursuant to an effective registration statement;
•Upon a sale of Series A Convertible Preferred Stock by Glencore in a Rule 144 transaction in which the shares of Series A Convertible Preferred Stock and our common stock issuable upon the conversion thereof are not directed to
any purchaser, such shares of Series A Convertible Preferred Stock sold will convert to shares of our common stock; and
•Immediately prior to and conditioned upon the consummation of a merger, reorganization or consolidation to which we are a party or a sale, abandonment, transfer, lease, license, mortgage, exchange or other disposition of all or substantially all of our property or assets, in one or a series of transactions where, in any such case, all of our common stock would be converted into the right to receive, or exchanged for, cash and/or securities, other than any transaction in which the Series A Convertible Preferred Stock will be redeemed.
Optional Conversion. Glencore has the option to convert the Series A Convertible Preferred Stock in a tender offer or exchange offer, at the same conversion ratio as above, in which a majority of the outstanding shares of our common stock have been tendered by the holders thereof and not duly withdrawn at the expiration time of such tender or exchange offer, so long as the Series A Convertible Preferred Stock is tendered or exchanged in such offer.
Stock Combinations – Adjustments. If, at any time while the Series A Convertible Preferred Stock is outstanding, Century combines outstanding common stock into a smaller number of shares, then the number of shares of common stock issuable on conversion of each share of Series A Convertible Preferred Stock will be decreased in proportion to such decrease in the aggregate number of shares of common stock outstanding.
Redemptions or Repurchases of Common Stock. We may not redeem or repurchase our common stock unless we redeem or repurchase, or otherwise make a payment on, a pro-rata number of shares of the Series A Convertible Preferred Stock. These restrictions do not apply to our open market repurchases or our repurchases pursuant to our employee benefit plans.
Right of Redemption. The Series A Convertible Preferred Stock will be redeemed by Century if any of the following events occur (at a redemption price based on the trading price of our common stock prior to the announcement of such event) and Glencore votes its shares of our common stock in opposition to such events:
•We propose a merger, reorganization or consolidation, sale, abandonment, transfer, lease, license, mortgage, exchange or other disposition of all or substantially all of our property or assets where any of our common stock would be converted into the right to receive, or exchanged for, assets other than cash and/or securities traded on a national stock exchange or that are otherwise readily marketable, or
•We propose to dissolve and wind up operations and any assets, other than cash and/or securities traded on a national stock exchange or that are otherwise readily marketable, are to be distributed to the holders of our common stock.
Stock Repurchase Program
In 2011, our Board of Directors authorized a $60.0 million stock repurchase program and during the first quarter of 2015, our Board of Directors increased the size of the program by $70.0 million. Under the program, Century is authorized to repurchase up to $130.0 million of our outstanding shares of common stock, from time to time, on the open market at prevailing market prices, in block trades or otherwise. The timing and amount of any shares repurchased will be determined by our management based on its evaluation of market conditions, the trading price of our common stock and other factors. The stock repurchase program may be suspended or discontinued at any time.
Shares of common stock repurchased are recorded at cost as treasury stock and result in a reduction of shareholders’ equity in the Consolidated Balance Sheets. From time to time, treasury shares may be reissued as contributions to our employee benefit plans and for the conversion of preferred stock. When shares are reissued, we use an average cost method for determining cost. The difference between the cost of the shares and the reissuance price is added to or deducted from additional paid-in capital.
Through December 31, 2024, we repurchased 7,186,521 shares of common stock for an aggregate purchase price of $86.3 million. We have made no repurchases since April 2015 and have approximately $43.7 million remaining under the repurchase program authorization as of December 31, 2024.
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Inventories
 12 Months Ended
Dec. 31, 2024
Inventory, Net [Abstract]  
Inventories Inventories
Inventories, at December 31, consist of the following:
 20242023
Raw materials$180.8 $162.5 
Work-in-process52.1 42.9 
Finished goods74.6 46.3 
Operating and other supplies231.5 225.3 
Inventories$539.0 $477.0 
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Property, Plant and Equipment
 12 Months Ended
Dec. 31, 2024
Property, Plant and Equipment [Abstract]  
Property, Plant and Equipment Property, Plant and Equipment
Property, plant and equipment, at December 31, consist of the following:
 20242023
Land and improvements$104.3 $105.1 
Mineral Reserves34.7 35.8 
Buildings and improvements404.3 328.8 
Machinery and equipment1,664.0 1,580.7 
Asset Retirement Obligation35.3 21.8 
Construction in progress44.7 160.3 
 2,287.3 2,232.5 
Less accumulated depreciation, amortization and depletion(1,309.0)(1,228.3)
Property, plant and equipment - net$978.3 $1,004.2 
For the years ended December 31, 2024, 2023 and 2022, we recorded depreciation, amortization and depletion expense of $81.8 million, $74.7 million, and $73.4 million, respectively.
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Accumulated Other Comprehensive Loss ("AOCL")
 12 Months Ended
Dec. 31, 2024
Additional financial information disclosures [Abstract]  
Accumulated Other Comprehensive Loss ("AOCL") Accumulated Other Comprehensive Loss ("AOCL")
Components of AOCL20242023
Defined benefit plan liabilities$(107.0)$(101.8)
Unrealized gain on financial instruments1.4 1.6 
Other comprehensive loss before income tax effect(105.6)(100.2)
Income tax effect(1)
2.3 2.3 
Accumulated other comprehensive loss$(103.3)$(97.9)
(1)The allocation of the income tax effect to the components of other comprehensive loss is as follows:
20242023
Defined benefit plan liabilities$2.6 $2.6 
Unrealized loss on financial instruments(0.3)(0.3)
The following table summarizes the changes in the accumulated balances for each component of AOCL:
Defined benefit plan and other postretirement liabilitiesUnrealized gain (loss) on financial instrumentsTotal, net of tax
Balance, December 31, 2021
$(84.0)$1.7 $(82.3)
Other comprehensive income (loss) before reclassifications(5.9)— (5.9)
Net amount reclassified to net income (loss)(5.7)(0.1)(5.8)
Balance, December 31, 2022
(95.6)1.6 (94.0)
Other comprehensive income (loss) before reclassifications(10.1)— (10.1)
Net amount reclassified to net income (loss)6.3 (0.1)6.2 
Balance, December 31, 2023
(99.4)1.5 (97.9)
Other comprehensive income (loss) before reclassifications(11.9)— (11.9)
Net amount reclassified to net income (loss)6.7 (0.2)6.5 
Balance, December 31, 2024
$(104.6)$1.3 $(103.3)
Reclassifications out of AOCL were included in the Consolidated Statements of Operations as follows:
Year Ended December 31,
AOCL ComponentsLocation202420232022
Defined benefit plan and other postretirement liabilitiesCost of goods sold$(8.5)$(1.0)$3.5 
Other income, net— — (8.9)
Selling, general and administrative expenses1.1 (0.2)3.3 
Other operating expense (income), net2.2 (2.6)(9.0)
Income tax expense— — (0.3)
Net of tax$(5.2)$(3.8)$(11.4)
Gain (loss) on financial instrumentsCost of goods sold$(0.2)$(0.1)$(0.2)
Income tax effect $— — (0.1)
Net of tax$(0.2)$(0.1)$(0.3)
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Pension and Other Postretirement Benefits
 12 Months Ended
Dec. 31, 2024
Retirement Benefits [Abstract]  
Pension and Other Postretirement Benefits Pension and Other Postretirement Benefits 
Pension Benefits
We maintain noncontributory defined benefit pension plans for certain foreign and domestic hourly and salaried employees. For the eligible domestic salaried employees, plan benefits are based primarily on years of service and average compensation during the later years of employment. For hourly employees, plan benefits are based primarily on a formula that provides a specific benefit for each year of service. Plan benefits are available to all permanent foreign employees. Our funding policy is to contribute amounts based upon actuarial and economic assumptions designed to achieve adequate funding of the projected benefit obligations and to meet the minimum funding requirements of the Employee Retirement Income Security Act of 1974 ("ERISA"). In addition, we maintain the supplemental executive retirement benefit ("SERB") plan for certain current and former executive officers, which is frozen to future accruals.
Other Postretirement Benefits ("OPEB")
In addition to providing pension benefits, we provide certain healthcare and life insurance benefits for certain foreign and domestic retired employees. We accrue the estimated cost of providing postretirement benefits during the working careers of those employees who could become eligible for such benefits when they retire. We fund these benefits as the retirees submit claims.
Retiree medical welfare changes
Under the current Hawesville labor agreement, employees who retire during the term of the labor agreement have been divided into sub-groups based on attributes such as Medicare eligibility, hire date, age and years of service. Levels of benefits are defined for the sub-groups and range from no substantive change from the benefits provided under the previous labor agreement to replacement of the defined retiree medical benefit program with individual health reimbursement accounts for each eligible participant. The health reimbursement accounts are funded based on established rates per hour worked by each eligible participant. Eligible participants will be able to withdraw from their health reimbursement accounts to fund their own retiree medical coverage.
During 2017, the Company amended its non-union retiree medical and life insurance benefits to align the Company’s benefits with the market and achieve a uniform retiree medical benefit design across the Company’s U.S. locations. Effective January 1, 2018, non-union retiree medical and life insurance benefits are restricted to current participants who meet the eligibility criteria as of January 1, 2018. Additionally, effective January 1, 2019, Century no longer administers non-union retiree medical, prescription drug, dental, or vision benefits and instead makes fixed health reimbursement account contributions.
Obligation and Funded Status
The change in benefit obligation and change in plan assets as of December 31 are as follows:
PensionOPEB
2024202320242023
Change in benefit obligation:    
Benefit obligation at beginning of year$305.1 $263.0 $76.8 $73.7 
Service cost4.0 3.3 0.2 0.1 
Interest cost17.2 17.3 3.9 3.9 
Plan amendments— 1.1 — — 
Actuarial (gain) loss(3.2)11.0 0.3 4.8 
Medicare Part D— — 0.2 0.3 
Acquisition— 28.6 — 0.8 
Benefits paid(21.4)(19.9)(5.7)(6.8)
Exchange rates(0.4)(0.5)— — 
Plan participants' contributions1.0 1.2 — — 
Benefit obligation at end of year$302.3 $305.1 $75.7 $76.8 
The decreases in both the defined benefit plans' and OPEB plans' benefit obligation were mainly driven by lower interest costs and actuarial gains in 2024, which were primarily attributable to the changes in the discount rates from fiscal year 2023 to 2024.
PensionOPEB
2024202320242023
Change in plan assets:    
Fair value of plan assets at beginning of year$256.8 $216.6 $— $— 
Actual return on plan assets6.8 21.4 — — 
Acquisition— 31.5 — — 
Employer contributions2.3 6.6 5.5 6.5 
Medicare Part D subsidy received— — 0.2 0.3 
Benefits paid(21.5)(19.9)(5.7)(6.8)
Exchange rates(0.3)(0.6)— — 
Plan participants' contributions1.0 1.2 — 
Fair value of assets at end of year$245.1 $256.8 $— $— 
The change in actual return on plan assets in 2024 was primarily attributable to fluctuations in market prices during the year.
 PensionOPEB
 2024202320242023
Funded status of plans:    
Funded status$(57.2)$(48.3)$(75.7)$(76.8)
Amounts recognized in the Consolidated Balance Sheets:
Current liabilities(1.8)(1.8)(6.5)(6.5)
Non-current liabilities(55.4)(46.5)(69.2)(70.3)
Net amount recognized$(57.2)$(48.3)$(75.7)$(76.8)
Amounts recognized in accumulated other comprehensive loss (pre-tax):  
Net loss$82.3 $82.1 $14.4 $14.8 
Prior service cost (benefit)1.6 1.8 — — 
Total$83.9 $83.9 $14.4 $14.8 
Pension Plans That Are Not Fully Funded
At December 31, 2024, the projected benefit obligation, accumulated benefit obligation and fair value of plan assets for the pension plans with accumulated benefit obligations in excess of plan assets were $302.3 million, $279.3 million, and $245.1 million, respectively.
At December 31, 2023, the projected benefit obligation, accumulated benefit obligation and fair value of plan assets for the pension plans with accumulated benefit obligations in excess of plan assets were $305.1 million, $305.9 million and $256.8 million, respectively.
Components of net periodic benefit cost and other amounts recognized in other comprehensive income (loss):
Net Periodic Benefit Cost:
 Year Ended December 31,
 PensionOPEB
 202420232022202420232022
Service cost$4.0 $3.3 $4.3 $0.2 $0.1 $0.2 
Interest cost17.2 17.3 10.3 3.9 3.9 2.9 
Expected return on plan assets(18.3)(17.3)(23.5)— — — 
Amortization of prior service costs0.2 0.1 0.1 — — (1.3)
Amortization of net loss5.8 6.0 3.5 0.7 0.1 1.3 
Net periodic benefit cost8.9 9.4 (5.3)4.8 4.1 3.1 
Curtailment benefit (1)
— — — — — (8.9)
Total benefit cost$8.9 $9.4 $(5.3)$4.8 $4.1 $(5.8)
(1)During 2022, we re-measured certain other postretirement benefits triggered by the Hawesville smelter curtailment, leading to a non-cash OPEB curtailment benefit totaling $8.9 million for the year ended December 31, 2022.
Other changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (pre-tax):
 Year Ended December 31,
 PensionOPEB
 2024202320242023
Net (gain) loss$8.4 $6.9 $0.3 $4.8 
Net loss (gain) transferred due to acquisition— (4.5)— (0.2)
Prior service cost (benefit)— 1.2 — — 
Amortization of net loss, including recognition due to settlement(5.8)(6.0)(0.7)(0.2)
Amortization of prior service (cost) benefit, including curtailment(0.2)(0.1)— — 
Exchange rates(2.4)(1.1)— (0.1)
Total amount recognized in other comprehensive income (loss)
— (3.6)(0.4)4.3 
Net periodic benefit cost8.9 9.4 4.8 4.1 
Total recognized in net periodic benefit cost and other comprehensive income (loss)
$8.9 $5.8 $4.4 $8.4 
Weighted average assumptions used to determine benefit obligations at December 31:
PensionOPEB
2024202320242023
Discount rate (1)
5.99%5.19%5.62%5.19%
Rate of compensation increase without Jamaica3.0%3.5%3.0%3.5%
Rate of compensation increase Jamaica7.0%n/a7.0%n/a
Measurement date12/31/202412/31/202312/31/202412/31/2023
Weighted average assumptions used to determine net periodic benefit cost for the years ended December 31:
 PensionOPEB
 202420232022202420232022
Measurement date12/31/202312/31/202212/31/202112/31/202312/31/202212/31/2021
Fiscal year end12/31/202412/31/202312/31/202212/31/202412/31/202312/31/2022
Discount rate (1)
6.75%5.50%2.94%5.43%5.57%2.64%
Rate of compensation increase without Jamaica (2)
3.5%
4%/3.5%
3%/3.5%
3.5%
4%/3.5%
3%/3.5%
Rate of compensation increase Jamaica9.0%n/an/a8.0%n/an/a
Expected return on plan assets (3)
7.28%7.25%7.25%—%—%—%
(1)We use the Ryan Above Median Yield Curve to determine the discount rate.
(2)For 2024, the rate of compensation increase is 3.5%. For 2023, the rate of compensation increase was 4% per year for the first year and 3.5% per year thereafter. For 2022, the rate of compensation increase was 3% per year for the first year and 3.5% per year thereafter.
(3)The rate for each of our defined benefit plans was selected by taking into account our expected asset mix and is based on historical performance as well as expected future rates of return on plan assets.
For measurement purposes, medical cost inflation for location other than Jamaica is initially estimated to be 8.5%, and 7.5% for pre- and post-65 participants, respectively, declining to 4.5% over ten years and continuing thereafter. For Jamaica, it is initially estimated to be 8.0% for both pre and post 65 participants and for the next two years.
Benefit Plan Assets
Pension Plan Investment Strategy and Policy
The Pension Plans’ assets are invested in a prudent manner for the exclusive purpose of providing benefits to participants.
Other objectives are to:
•Provide a total return that, over the long term, provides sufficient assets to fund the pension plan liabilities subject to a level of risk, contributions and pension expense deemed appropriate by the company.
•Minimize, where possible, pension expense volatility, and inclusion of liability driven investing as an investment strategy when appropriate. As the funding ratio improves, the objectives will evolve to minimize the funded status volatility.
•Diversify investments within asset classes to reduce the impact of losses in single investments.
The assets of the Pension Plans are invested in compliance with ERISA, as amended, and any subsequent applicable regulations and laws.
Performance
Our performance objective is to outperform the return of weighing passive investment alternatives by the policy target allocations after fees at a comparable level of risk. This investment objective is expected to be achieved over the long term and is measured over rolling multi-year periods. Peer-relative performance comparisons will also be considered especially when performance deviates meaningfully from market indexes. Investment objectives for each asset class are included below.
Asset Allocation Policy
Asset allocation policy is the principal method for achieving the Pension Plans' investment objectives stated above. The Pension Plans’ weighted average long-term strategic asset allocation policy targets are as follows:
 Pension Plan Asset Allocation
 2024 TargetDecember 31, 2024December 31, 2023
Return seeking assets:
Global equity50%51%44%
Diversified credit15%17%15%
Real assets10%11%10%
Liability hedging assets25%20%28%
Cash—%1%3%
 100%100%100%
Global equities are held for their long-term expected return premium over fixed income investments and inflation. Fixed income is held for diversification relative to equities, and as a hedging instrument to interest rate volatility for the pension obligation. Diversified Credit and Real Assets are held for diversification relative to equities and for income generation.
The strategic role of global equities is to:
•Provide higher expected returns of the major asset classes.
•Maintain a diversified exposure within global stock markets through the use of multi-manager portfolio strategies.
The strategic role of fixed income is to:
•Diversify the Pension Plans’ equity exposure by investing in fixed income securities that exhibit a low correlation to equities, thereby lowering the overall return volatility of the entire investment portfolio.
•Maintain a diversified exposure within the U.S. fixed income market through the use of portfolio strategies targeting treasury bond exposures.
•Hedge the interest rate risk of the pension obligation by investing in securities that target a similar duration to the pension obligation cash flows.
The strategic role of diversified credit is to:
•Diversify the Pension Plans’ equity exposure by investing in alternative credit securities that exhibit a low correlation to equities, thereby lowering the overall return volatility of the entire investment portfolio.
•Maintain a diversified exposure within the alternative credit markets through the use of multi-manager portfolio strategies targeting, but not limited to, securitized credit, high yield securities, and emerging market debt.
•Achieve returns in excess of passive indexes through the use of active investment managers and strategies.
The strategic role of real assets is to:
•Diversify the Pension Plans’ equity exposure by investing in real assets that exhibit a low correlation to equities, thereby lowering the overall return volatility of the entire investment portfolio.
•Maintain a diversified exposure within the real asset markets through the use of multi-manager portfolio strategies targeting listed and unlisted exposures.
•Achieve returns in excess of passive indexes through the use of active investment managers and strategies.
The long-term strategic asset allocation policy is reviewed regularly or whenever significant changes occur to Century’s or the Pension Plans' financial position and liabilities.
Fair Value Measurements of Pension Plan assets
The following table sets forth by level the fair value hierarchy our Pension Plans' assets. These assets are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the valuation of fair value assets and liabilities and the placement within the fair value hierarchy levels.
As more fully described within Note 7. Fair Value Measurements, the Company uses a three-level fair value hierarchy that prioritizes the inputs used to measure fair values. The fair value hierarchy provides transparency regarding the inputs we use to measure fair value. We categorize each fair value measurement in its entirety into the following three levels, based on the lowest level input that is significant to the entire measurement:
•Level 1 Inputs – quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date.
•Level 2 Inputs – inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.
•Level 3 Inputs – unobservable inputs for the asset or liability.
The following summarizes the Company’s Pension Plans' assets fair value by asset category:
As of December 31, 2024
Level 1Level 2Level 3Assets measured at NAVTotal
Cash and cash equivalents$0.7 $— $— $2.8 $3.5 
Global Equity20.0 — — 108.1 128.1 
Diversified Credit11.8 — — 35.3 47.1 
Real Assets— — — 23.1 23.1 
Liability hedging assets— — — 42.6 42.6 
Other
0.1 0.6 — — 0.7 
Total plan assets fair value$32.6 $0.6 $— $211.9 $245.1 
As of December 31, 2023
Cash and cash equivalents$0.4 $— $— $4.6 $5 
Global Equity19.7 — — 100.0 119.7 
Diversified Credit11.2 — — 34.7 45.9 
Real Assets— — — 22.8 22.8 
Liability hedging assets— — — 62.7 62.7 
Other
0.1 0.6 — — 0.7 
Total plan assets fair value$31.4 $0.6 $— $224.8 $256.8 
Our domestic Pension Plans’ assets are held in certain commingled funds and group trusts which do not have publicly quoted prices. The fair value of the commingled funds and group trusts is based on NAV of the underlying investments. The fair value of the underlying investments held by the commingled funds, separate accounts and common collective trusts is generally based on quoted prices in active markets. Though the Company believes the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value. Our foreign plan assets are held in bonds and equity securities which have publicly quoted prices.
Our other postretirement benefit plans are unfunded. We fund these benefits as the retirees submit claims.
Pension and OPEB Cash Flows
During 2024 and 2023, we made contributions of approximately $2.3 million and $6.6 million, respectively, to the qualified defined benefit and SERB plans we sponsor and $5.5 million and $6.5 million, respectively, to the other postretirement benefit plans.
We expect to make the following contributions for 2025:
2025
Expected pension plan contributions$8.0 
Expected OPEB benefits payments6.4 
Estimated Future Benefit Payments
The following table provides the estimated future benefit payments for the pension and other postretirement benefit plans:
 Pension BenefitsOPEB Benefits
2025$20.5 $6.5 
202620.9 6.5 
202720.9 6.5 
202821.4 6.7 
202921.7 6.5 
2030 – 203494.8 30.9 
Participation in Multi-employer Pension Plans
The union-represented employees at Hawesville are part of a United Steel, Paper and Forestry, Rubber, Manufacturing, Energy, Allied Industrial and Service Workers International Union ("USWA") sponsored multi-employer plan. Our contributions to the plan are determined at a fixed rate per hour worked. Currently, we do not have any plans to withdraw from or curtail participation in this plan. The risks of participating in a multi-employer plan are different from single-employer plans in the following respects:
•Assets contributed to the multi-employer plan by one employer may be used to provide benefits to employees of other participating employers.
•If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers.
•If a participating employer chooses to stop participating in a multi-employer plan, the employer may be required to pay the plan an amount based on the underfunded status of the plan, referred to as a withdrawal liability.
Century’s participation in the plan for the year ended December 31, 2024, is outlined in the table below.
FundSteelworkers Pension Trust
EIN / PN23-6648508 / 499
Pension Protection Act Zone Status 2023 (1)
 Green
Pension Protection Act Zone Status 2022 (1)
 Green
Subject to Financial Improvement/Rehabilitation Plan (2)
 No
Contributions of Century Aluminum 2024$0.04
Contributions of Century Aluminum 2023$0.2
Contributions of Century Aluminum 2022$1.6
Withdrawal from Plan ProbableNo
Surcharge Imposed No
Expiration Date of Collective Bargaining Agreement (2)
March 31, 2026
(1)The most recent Pension Protection Act zone status available in 2024 and 2023 is for the plan's year-end December 31, 2023 and December 31, 2022, respectively. The zone status is based on information that Century received from the plan as well as publicly available information per the Department of Labor and is certified by the plan’s actuary. Among other factors, plans in the green zone are at least 80 percent funded.
(2)The “Subject to Financial Improvement / Rehabilitation Plan” column indicates plans for which a financial improvement plan (FIP) or a rehabilitation plan (RP) is either pending or has been implemented. The last column lists the expiration date(s) of the collective-bargaining agreement(s) to which the plans are subject.

Century's contributions to the above plan is not 5% or more of the total contributions to the plan.
Century 401(k) Plans
We sponsor a tax-deferred savings plan under which eligible domestic employees may elect to contribute specified percentages of their compensation with Century. We match a portion of participants' contributions to the savings plan. Employee and matching contributions are considered fully vested immediately upon participation in the plan. Concurrent with the 2014 amendment to the Salaried Pension Plan that eliminated future accruals for participants who are under age 50 as of January 1, 2015 and closed the plan to new entrants, the Company increased the proportional match of contributions made to those affected by the amendment. The expense related to the plan was $6.3 million, $5.8 million, and $6.0 million for 2024, 2023, and 2022, respectively.
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Share-based Compensation
 12 Months Ended
Dec. 31, 2024
Share-Based Payment Arrangement [Abstract]  
Share-based Compensation Share-based Compensation
Amended and Restated Stock Incentive Plan. Under our Amended and Restated Stock Incentive Plan (the "Stock Incentive Plan") we award service-based and performance-based share awards and nonqualified stock options to our salaried officers, non-employee directors, and other key employees. Our service-based and performance-based share awards typically vest over a period of three years from the date of grant, provided that the recipient is still our employee at the time of vesting. Our independent non-employee directors receive annual grants of service-based share awards that typically vest following 12 months of service. The Stock Incentive Plan has 12,900,000 shares authorized for issuance with approximately 2,673,311 shares remaining at December 31, 2024.
Long-Term Incentive Plan. We also grant annual long-term incentive awards under our Amended and Restated Long-Term Incentive Plan (the "LTIP"). The LTIP is designed to provide senior-level employees the opportunity to earn long-term incentive awards through the achievement of performance goals and to align compensation with the interests of our stockholders. This is achieved by linking compensation to share price appreciation and total stockholder return over a multi-year period. Awards made under the LTIP are granted subject to the Stock Incentive Plan to the extent the award is deliverable in stock. We provide two types of LTIP awards: restricted stock units ("RSU") and performance stock units ("PSU").
RSUs are stock-settled awards which do not contain any performance-based vesting requirements. PSUs can be settled in cash or stock and vest based on the achievement of pre-determined performance metrics at the discretion of the Board. Our PSU liability was approximately $7.1 million and $3.3 million as of December 31, 2024 and 2023, respectively. Both the PSUs and RSUs vest, in their entirety, after three years.
Service-based share awardsNumber
Outstanding at January 1, 2024
1,156,774 
Granted650,755 
Vested(263,227)
Forfeited(139,407)
Outstanding at December 31, 2024
1,404,895 
Performance-based share awardsNumber
Outstanding at January 1, 2024
602,564 
Granted475,226 
Vested(303,315)
Forfeited— 
Outstanding at December 31, 2024
774,475 
 Year ended December 31,
Service-based share awards202420232022
Weighted average per share fair value of service-based share grants$10.11 $12.58 $17.30 
Fair Value Measurement of Share-Based Compensation Awards. We estimate the fair value of each stock option award using the Black-Scholes model on the date of grant. Our last grant of stock options, awarded in 2009, expired in May 2019. We
have not granted any stock options since 2009. For our service-based awards, fair value is equal to the closing stock price on the date of grant. For our performance-based awards, fair value is equal to the closing stock price at each reporting period end.
The following table summarizes the compensation cost recognized for the years ended December 31, 2024, 2023 and 2022 for all service-based and performance-based share awards. The compensation cost is included as part of selling, general and administrative expenses and cost of goods sold in our Consolidated Statements of Operations.
Year ended December 31,
202420232022
Share-based compensation (benefit) expense reported:   
Performance-based share (benefit) expense$9.3 $2.0 $(5.0)
Service-based share expense6.1 4.6 4.4 
Total share-based compensation (benefit) expense before income tax15.4 6.6 (0.6)
Income tax— — — 
Total share-based compensation (benefit) expense, net of income tax$15.4 $6.6 $(0.6)
No share-based compensation cost was capitalized during these periods and there were no significant modifications of any share-based awards in 2024, 2023 and 2022. As of December 31, 2024, we had unrecognized compensation cost of $13.2 million before taxes. This cost will be recognized over a weighted average period of 1.7 years.
v3.25.0.1
Earnings Per Share
 12 Months Ended
Dec. 31, 2024
Earnings Per Share [Abstract]  
Earnings Per Share Earnings Per Share
Basic EPS amounts are calculated by dividing net income (loss) allocated to common stockholders by the weighted average number of common shares outstanding. Diluted EPS amounts assume the issuance of common stock for all potentially dilutive common shares outstanding.
The following table shows the basic and diluted earnings (loss) per share for 2024, 2023, and 2022:
For the year ended December 31, 2024
Net Income
Shares
(in millions)
Per Share
Net income attributable to Century stockholders
$336.8 
Less: net income allocated to participating securities17.9 
Basic EPS:   
Net income allocated to common stockholders$318.9 92.8 $3.44 
Effect of Dilutive Securities(1):
Share-based compensation— 1.0 
 Convertible senior notes 2.7 4.6 
Diluted EPS:
Net income allocated to common stockholders
$321.6 98.4 $3.27 
For the year ended December 31, 2023
Net Loss
Shares
(in millions)
Per Share
Net loss attributable to Century stockholders$(43.1)
Amount allocated to common stockholders100 %
Basic and Diluted EPS:(1)
$(43.1)92.4 $(0.47)
For the year ended December 31, 2022
Net Loss
Shares
(in millions)
Per Share
Net loss attributable to Century stockholders$(14.1)  
Amount allocated to common stockholders100 %  
Basic and Diluted EPS:(1)
$(14.1)91.4 $(0.15)
Securities excluded from the calculation of diluted EPS (in millions)(1):
2024
2023
2022
Share-based compensation
0.6 1.0 1.7 
Convertible preferred shares5.2 5.4 5.8 
Convertible senior notes— 4.6 4.6 
(1)In periods when we report a net loss, all share-based compensation awards, convertible preferred shares and convertible senior notes are excluded from the calculation of diluted weighted average shares outstanding because of their anti-dilutive effect on earnings (loss) per share.
v3.25.0.1
Income Taxes
 12 Months Ended
Dec. 31, 2024
Income Tax Disclosure [Abstract]  
Income Taxes Income Taxes
The components of pre-tax book income (loss) consist of the following:
Year Ended December 31,
202420232022
U.S.$335.5 $78.0 $(193.6)
Foreign (11.7)(144.8)227.0 
Total $323.8 $(66.8)$33.4 
Significant components of income tax expense consist of the following:
Year Ended December 31,
202420232022
Current:   
U.S. federal current expense (benefit)$— $0.5 $— 
State current expense (benefit)— — 0.2 
Foreign current expense (benefit)4.9 15.8 4.0 
Total current expense (benefit)4.9 16.3 4.2
Deferred:   
U.S. federal deferred benefit— (0.3)(0.3)
State deferred benefit— (0.1)— 
Foreign deferred tax (benefit) expense(1.7)(30.5)43.5 
Total deferred (benefit) expense(1.7)(30.9)43.2 
Total income tax (benefit) expense$3.2 $(14.6)$47.4 
A reconciliation of the statutory U.S. Federal income tax rate to the effective income tax rate on income (loss) is as follows:
Year Ended December 31,
 202420232022
Federal Statutory Rate21.0 %21.0 %21.0 %
Permanent differences1.0 1.1 (15.2)
State taxes, net of Federal benefit— (0.1)0.1 
Rate change(0.5)(0.3)0.4 
Foreign earnings taxed at different rates than U.S.— 2.0 (0.8)
Valuation allowance(11.3)3.6 (4.2)
Foreign dividends and inclusions0.5 (12.7)122.9 
Net operating loss expiration and remeasurement2.8 (8.0)43.1 
Filing differences8.7 0.6 (19.1)
Changes in uncertain tax reserves0.2 (1.3)(5.3)
Advanced Manufacturing Production Credit(5.9)18.6 — 
Bargain Purchase gain
(15.7)— — 
Other0.2 (2.7)(0.9)
Effective tax rate1.0 %21.8 %142.0 %
The effective tax rate for the year ending December 31, 2024 was 1.0% compared to the statutory US tax rate of 21%. This lower effective rate is primarily due to the bargain purchase gain recognized for US GAAP purposes but not for US tax purposes, as well as the non-taxable benefit of the Advanced Manufacturing Credit under Section 45X, which is discussed below.
In August 2022, the IRA became law. The IRA provides several tax incentives to promote clean energy and the production of critical minerals in the U.S., including a refundable tax credit, pursuant to Section 45X of the Internal Revenue Code. Tax credits, such as refundable credits whose realization does not depend on the entity’s generation of taxable income like the refundable tax credit provided by the IRA are not considered an element of income tax accounting under ASC 740. After considering US GAAP, the Company has concluded it is appropriate to apply IAS 20, Accounting for Government Grants and Disclosure of Government Assistance, to account for the refundable tax credit as an income grant.
Section 45X of the IRA contains a production tax credit equal to 10% of certain eligible production costs, including, without limitation, labor, energy, depreciation and amortization and overhead expenses. On December 14, 2023, the U.S. Department of the Treasury and the Internal Revenue Service released proposed rules to provide guidance on the production tax credit requirements under Internal Revenue Code Section 45X (the “Proposed Regulations”). On October 24, 2024 the U.S. Department of the Treasury and the Internal Revenue Service released final regulations regarding the advanced manufacturing production credit established by the Inflation Reduction Act of 2022 to incentivize the production of eligible components within the United States (the “Final Regulations”).
The Final Regulations provide guidance on rules that taxpayers must satisfy to qualify for the Section 45X tax credit. One of the most significant changes from the Proposed Regulations is that the final regulations allow certain direct and indirect material costs to be included in the section 45X credit computation for the production of electrode active materials and critical minerals. Notably, with respect to all of the comments related to the definition of aluminum, the Treasury Department and the IRS have determined that additional consideration is necessary prior to finalizing proposed § 1.45X–4(b)(1), which the Treasury Department and the IRS intend to do at a later date. For that reason, § 1.45X–4(b)(1) is reserved in these Final Regulations. For the year ended December 31, 2024 and December 31, 2023, we recognized $89.7 million and $56.5 million as a reduction in Cost of goods sold, and $2.9 million and $2.8 million as a reduction in selling, general and administrative expenses, respectively, within the Consolidated Statements of Operations. As of December 31, 2024 and December 31, 2023, the Company recognized a current manufacturing credit receivable of $81.5 million and $59.3 million, respectively. As of December 31, 2024, the Company recognized a non-current manufacturing credit receivable of $70.4 million. There was no non-current manufacturing credit receivable recognized as of December 31, 2023 within the Consolidated Balance Sheets.
The Company’s accounting policy with respect to releasing income tax effects from accumulated other comprehensive income is to apply a security by security approach whereby the tax effects are measured based on the change in the unrealized
gains or losses reflected in other comprehensive loss.
Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes.
The significant components of our deferred tax assets and liabilities as of December 31 are as follows:
20242023
Deferred tax assets:  
Accrued postretirement benefit cost$30.1 $30.7 
Net operating losses 473.3 467.6 
Disallowed interest expense37.1 29.2 
Derivative and hedging contracts0.1 1.2 
Fixed asset tax over book basis— 9.2 
Other29.4 28.3 
Total deferred tax assets570.0 566.2 
Valuation allowance(504.4)(537.6)
Net deferred tax assets$65.6 $28.6 
Deferred tax liabilities:  
Fixed asset book over tax basis(115.9)(62.0)
Derivatives— — 
Foreign basis differences0.6 (18.1)
Other(21.4)(20.6)
Total deferred tax liabilities(136.7)(100.7)
Net deferred tax liability$(71.1)$(72.1)
We regularly assess the likelihood that deferred tax assets will be recovered from future taxable income. To the extent we believe that it is more likely than not that a deferred tax asset will not be realized, a valuation allowance is established. When a valuation allowance is established or increased, an income tax charge is included in the Consolidated Statements of Operations and net deferred tax assets are adjusted accordingly. Future changes in tax laws, statutory tax rates and taxable income levels could result in actual realization of the deferred tax assets being materially different from the amounts provided for in the consolidated financial statements. If the actual recovery amount of the deferred tax asset is less than anticipated, we would be required to write-off the remaining deferred tax asset and increase the tax provision.
We have a valuation allowance of $504.4 million recorded against our net U.S. and Jamaican deferred tax assets, and a portion of our Icelandic deferred tax assets as of December 31, 2024. The Company is subject to the provisions of ASC 740-10, Income Taxes, which requires that the effect on deferred tax assets and liabilities of a change in tax rates be recognized in the period the tax rate change was enacted.
The changes in the valuation allowance are as follows:
Year Ended December 31,
202420232022
Beginning balance, valuation allowance$537.6 $487.9 $485.8 
Remeasurement of deferred tax assets— — — 
Release of valuation allowance— — — 
Expiration of net operating losses(6.1)(7.2)(15.4)
Other change in valuation allowance(27.1)56.9 17.5 
Ending balance, valuation allowance$504.4 $537.6 $487.9 
The significant components of our NOLs are as follows:
20242023
Federal (1)
$1,571.2 $1,533.5 
State (2)
1,163.5 1,221.0 
Foreign (3)(4)
342.2 344.4 
(1)US federal NOLs begin to expire in 2028.
(2)US state NOLs begin to expire in 2027.
(3)NOLs in Iceland expire between 2025 and 2026.
(4)NOLs in Jamaica do not expire.
Our ability to utilize our deferred tax assets to offset future federal taxable income may be significantly limited if we experience an "ownership change" as defined in the Code. In general, an ownership change would occur if our "five-percent shareholders," as defined under the Code, collectively increase their ownership in us by more than 50 percentage points over a rolling three-year period. Future transactions in our stock that may not be in our control may cause us to experience such an ownership change and thus limit our ability to utilize net operating losses, tax credits and other tax assets to offset future taxable income.
A reconciliation of the beginning and ending amounts of gross unrecognized tax benefits (excluding interest) is as follows:
202420232022
Balance as of January 1,  $3.0 $2.2 $4.0 
Additions based on tax positions related to the current year0.6 1.3 0.3 
Decreases due to lapse of applicable statute of limitations(0.1)(0.5)(2.1)
Balance as of December 31,$3.5 $3.0 $2.2 
As of December 31, 2024, the Company’s gross unrecognized tax benefits totaled $3.5 million. After considering the deferred tax accounting impact, it is expected that about $1.4 million of the total as of December 31, 2024 would favorably affect the effective tax rate if resolved in the Company’s favor. Included in the above balances are tax positions relating to temporary differences where there is uncertainty about the timing of tax return inclusion, but not that the amounts will ultimately be tax deductible. Because of the impact of deferred tax accounting, other than interest and penalties, the timing would not impact the annual effective tax rate but could accelerate the payment of cash to the taxing authority to an earlier period. We do not expect a significant change in the balance of unrecognized tax benefits within the next twelve months. It is our policy to recognize potential accrued interest and penalties related to unrecognized tax benefits in income tax expense.
Century and its subsidiaries file income tax returns in the U.S. federal jurisdiction, various state and local jurisdictions, and several foreign jurisdictions.
Our federal income tax returns have been reviewed by the IRS through 2010. However, we have NOLs beginning in 2008 that are available for carryforward to future years. Under U.S. tax law, NOLs may be adjusted by the IRS until the statute of limitations expires for the year in which the NOL is used. Accordingly, our 2008 and later NOLs may be reviewed until they are used or expire.
We are subject to examination by tax authorities according to statutory periods defined in each jurisdiction. The earliest statutory period open is beginning in 2019.
v3.25.0.1
Commitments and Contingencies
 12 Months Ended
Dec. 31, 2024
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Commitments and Contingencies
We have pending against us or may be subject to various lawsuits, claims and proceedings related primarily to employment, commercial, stockholder, environmental, safety and health matters and are involved in other matters that may give rise to contingent liabilities. While the results of such matters and claims cannot be predicted with certainty, we believe that the ultimate outcome of any such matters and claims 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 and estimating liabilities, should
the resolution or 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 or environmental 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. While we regularly review the status of, and our estimates of potential liability associated with, contingencies to determine the adequacy of any associated accruals and related disclosures, the ultimate amount of loss may differ from our estimates.
Legal Contingencies
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 ("CAWV Retirees"), 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. On August 18, 2017, the District Court for the Southern District of West Virginia approved a settlement agreement in respect of these actions, pursuant to the agreement, CAWV agreed to make payments into a trust for the benefit of the CAWV Retirees in the aggregate amount of $23.0 million over the course of 10 years. Upon approval of the settlement, we paid $5.0 million to the aforementioned trust in September 2017 and recognized a gain of $5.5 million to arrive at the-then net present value of $12.5 million. CAWV has agreed to pay the remaining amounts under the settlement agreement in annual increments of $2.0 million for nine years. As of December 31, 2024, $2.0 million was recorded in other current liabilities and $1.6 million was recorded in other liabilities.
PBGC Settlement
In 2013, we entered into a settlement agreement with the Pension Benefit Guarantee Corporation ("the PBGC") regarding an alleged "cessation of operations" at our Ravenswood facility (the "PBGC Settlement Agreement"). Pursuant to the terms of the PBGC Settlement Agreement, we agreed to make additional contributions (above any minimum required contributions) to our defined benefit pension plans totaling approximately $17.4 million. Under certain circumstances, in periods of lower primary aluminum prices relative to our cost of operations, we were able to defer one or more of these payments, provided that we provide the PBGC with acceptable security for such deferred payments. We historically elected to defer certain payments under the PBGC Settlement Agreement and provided the PBGC with the appropriate security. On October 1, 2021, we amended the PBGC Settlement Agreement (the "Amended PBGC Settlement Agreement") such that we removed the deferral mechanism and agreed to contribute approximately $2.4 million per year to our defined benefit pension plans for a total of approximately $9.6 million, over four years beginning on November 30, 2022 and ending on November 30, 2025, subject to acceleration if certain terms and conditions are met in such amendment. As of December 31, 2024, we have made contributions of $7.2 million related to the Amended PBGC Settlement Agreement.
Power Commitments and Contingencies
Hawesville
Hawesville has a power supply arrangement with Kenergy and Century Marketer, LLC (“Century Marketer"), Century's wholly-owned subsidiary that acts as a MISO market participant. Under this arrangement, Hawesville gets access to power at Midcontinent Independent System Operator ("MISO") pricing plus transmission and other costs. As the MISO Market Participant, Century Marketer purchases power from MISO for resale to Kenergy, which then resells the power to Hawesville. Century Marketer's power supply arrangement with Kenergy has an effective term through May 31, 2028, with automatic one-year extensions unless either party provides one-year notice of termination prior to the May 31 anniversary date. Similarly, Kenergy's power supply contract with Hawesville has a term through December 31, 2026, with automatic one-year extensions unless either party provides one-year notice of termination prior to the December 31 anniversary date.
Sebree
Sebree has a power supply arrangement with Kenergy and Century Marketer. Under this arrangement, Sebree gets access to power at Midcontinent Independent System Operator ("MISO") pricing plus transmission and other costs. As the MISO Market Participant, Century Marketer purchases power from MISO for resale to Kenergy, which then resells the power to Sebree. Century Marketer's power supply arrangement with Kenergy has an effective term through May 31, 2028, with automatic one-year extensions unless either party provides one-year notice of termination prior to the May 31 anniversary date. Similarly, Kenergy's power supply contract with Hawesville has a term through December 31, 2026, with automatic one-year extensions unless either party provides one-year notice of termination prior to the December 31 anniversary date.
Mt. Holly
Century Aluminum of South Carolina ("CASC") has a power supply agreement with Santee Cooper that has an effective term through December 2026. Under this power supply agreement, 100% of Mt. Holly’s electrical power requirements are supplied from Santee Cooper’s generation at cost of service based rates.
Grundartangi
Grundartangi has power purchase agreements for approximately 545 MW with HS Orka hf ("HS"), Landsvirkjun and Orkuveita Reykjavikur ("OR"). These power purchase agreements expire on various dates from 2026 through 2036 (subject to extension). The power purchase agreements with each of HS and OR provide power at LME-based variable rates for the duration of these agreements. The larger Landsvirkjun agreement provides for fixed rate with an additional variable rate linked to the LME. Grundartangi also has a separate 25 MW power purchase agreement with Landsvirkjun at an LME-based variable rate.
Other Commitments and Contingencies
Labor Commitments
The bargaining unit employees at our Grundartangi, Vlissingen, Hawesville, Sebree and Jamalco facilities are represented by labor unions, representing approximately 59% of our total workforce.
Approximately 86% of Grundartangi’s work force is represented by five labor unions, governed by a labor agreement that establishes wages and work rules for covered employees. This agreement was effective Through December 31, 2024. Grundartangi is currently in the process of negotiating a new contract. Until a new contract is reached, employees will continue to operate under the current agreement.
100% of Vlissingen’s workforce is represented by the Federation for the Metal and Electrical Industry ("FME"), a Netherlands' employers' organization for companies in the metal, electronics, electrical engineering and plastic sectors. The FME negotiates working conditions with trade unions on behalf of its members, which, when agreed upon, are then applicable to all employees of Vlissingen. The current labor agreement is effective Through December 31, 2025.
Approximately 39% of our U.S. based work force is represented by USW through separately negotiated labor agreements for each facility. The labor agreement for Hawesville employees is effective Through April 1, 2026. Upon announcement of the curtailment, Hawesville and the USW local union entered into effects bargaining. An agreement was reached on July 19, 2022, covering the curtailment period. Century Sebree's labor agreement with USW for its employees is effective through October 28, 2028. Mt. Holly employees are not represented by a labor union.
Approximately 61% of Jamalco's work force is represented by the Union of Technical, Administrative, and Supervisory Personnel ("UTASP") through separately labor agreements for hourly and salaried employee groups. Both contracts were effective through December 31, 2023. Jamalco is currently in the process of negotiating new contracts with both the salaried and hourly employee groups. Until new contracts are reached, employees will continue to operate under the current agreements.
Contingent Obligation
We have a contingent obligation in connection with the “unwind” of a contractual arrangement between CAKY, Big Rivers Electric Corporation ("Big Rivers") and a third party and the execution of a long-term cost-based power contract with Kenergy, a member of a cooperative of Big Rivers, in July 2009. This contingent obligation consists of the aggregate payments
made to Big Rivers by the third party on CAKY’s behalf in excess of the agreed upon base amount under the long-term cost-based power contract with Kenergy. As of December 31, 2024, the principal and accrued interest for the contingent obligation was $32.3 million, which was fully offset by a derivative asset. We may be required to make installment payments for the contingent obligation in the future. These payments are contingent based on the LME price of primary aluminum and the level of Hawesville’s operations. Interest accrues at an annual rate equal to 10.94%. As of December 31, 2024, the LME forward market prices do not exceed the threshold for payment. In addition, based on the current level of Hawesville's operations, including the curtailment, we believe that we will not be required to make payments on the contingent obligation during the term of the agreement, which expires in 2028. There can be no assurance that circumstances will not change thus accelerating the timing of such payments.
v3.25.0.1
Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2024
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligations Asset Retirement Obligations
The reconciliation of the changes in our AROs is presented below:
Year ended December 31,
20242023
Beginning balance$51.1 $21.2 
Additional ARO liabilities incurred6.7 3.1 
ARO liabilities settled(4.6)(1.5)
Accretion expense2.1 2.0 
Acquired ARO liabilities (See Note 2)— 23.9 
Revisions in estimated cash flows10.8 2.4 
Ending balance$66.1 $51.1 
Current portion of asset retirement obligations (1)
4.6 1.6 
Asset retirement obligations - less current portion$61.5 $49.5 
(1) Current portion of asset retirement obligations is recorded in accrued and other current liabilities.
v3.25.0.1
Business Segments
 12 Months Ended
Dec. 31, 2024
Segment Reporting [Abstract]  
Business Segments Business Segments
Century Aluminum is a producer of primary aluminum, which trades as a global commodity, and owns a 55% interest in an alumina refinery joint venture. We are organized as a holding company with each of our operating primary aluminum smelters managed and operated as a separate facility reporting to our corporate headquarters. Our three operating primary aluminum smelters and our bauxite and alumina refinery each meet the definition of an operating segment We evaluated the similar economic and other characteristics, including similar products, production processes, customers and distribution and have aggregated our four operating segments into one reportable segment. In addition, all of our operating segments share several key economic factors inherent in their common products and production processes. For example, all of our facilities' revenue is based on market pricing. Our facilities have a similar customer base and utilize similar distribution methods to ship products. In 2024, we determined that our fully curtailed Hawesville facility no longer met the definition of an operating segment. Our chief executive officer is our chief operating decision maker (CODM) and evaluates performance based on Segment EBITDA (Earnings before interest, taxes, depreciation, and amortization). Specifically, the CODM reviews Segment EBITDA to develop forecasting and evaluate overall profitability performance.
A reconciliation of our consolidated assets to the total of primary aluminum segment assets and capital expenditures is provided below.
Segment assets (1)
202420232022
Aluminum$1,896.6 $1,808.1 $1,432.4 
Corporate, unallocated42.8 38.4 39.6 
Total assets$1,939.4 $1,846.5 $1,472.0 
Capital expenditures$82.3 $95.0 $86.3 
(1)Segment assets include accounts receivable, due from affiliates, prepaid and other current assets, leases - right of use assets, inventory, intangible assets and property, plant and equipment, net; the remaining assets are unallocated corporate assets.
Geographic information
Our net sales are attributed to geographic area based on the location of the selling operation. Included in the consolidated financial statements are the following amounts related to geographic locations:
 202420232022
Net sales: (1)
   
United States$1,427.0 $1,358.6 $1,737.2 
Iceland793.3 826.8 1,040.1 
Total Net sales
2,220.3 2,185.4 2,777.3 
Long-lived assets: (2)
   
United States$233.6 $219.1 $244.9 
Iceland526.4 529.4 491.0 
Jamaica255.2 275.8 — 
Other50.6 55.1 58.3 
(1)Includes sales of primary aluminum, scrap aluminum and alumina, and purchased aluminum and alumina.
(2)Includes long-lived assets other than financial instruments and deferred taxes.
Major customer information
Revenues from one customer in 2024 and 2023 and two customers in 2022 exceeded 10% of our net sales. A loss of these customers could have a material adverse effect on our results of operations. The net sales related to the customers is as follows:
Year Ended December 31,
202420232022
Glencore$1,312.1 $1,612.1 $1,671.1 
Southwire— — 331.3 
The following table presents our segment information to reconcile to Segment EBITDA for the periods indicated and, because we only have one segment, our net income (loss) attributable to Century stockholders is identical to the information presented in the Consolidated Statements of Operations:
Year Ended December 31,
202420232022
Net sales$2,220.3 $2,185.4 $2,777.3 
Segment Cost of goods sold(1)
(2,014.7)(2,056.9)(2,597.0)
IRA Credit - Cost of goods sold(2)
89.7 56.5 — 
Asset impairment
— — (159.4)
Other segment items(3)
(25.4)(55.7)(12.9)
Segment EBITDA
269.9 129.3 8.0 
Depreciation, depletion, and amortization - Cost of goods sold(86.5)(80.7)(76.4)
Selling, general and administrative expenses(56.8)(44.3)(37.5)
Interest expense - affiliates(6.7)(1.8)— 
Interest expense(36.4)(33.7)(29.3)
Interest income2.1 2.0 0.5 
Net gain (loss) on forward and derivative contracts - nonaffiliates2.5 (62.4)210.4 
Net gain (loss) on forward and derivative contracts - affiliates(0.5)0.6 (13.3)
Bargain purchase gain245.9 — — 
Other(4)
(9.7)24.1 (29.1)
Income tax benefit (expense)(3.2)14.6 (47.4)
Net income (loss)320.6 (52.3)(14.1)
Net loss attributable to noncontrolling interests
16.2 9.2 — 
Net income (loss) attributable to Century stockholders, as reported$336.8 $(43.1)$(14.1)
(1)Includes raw materials, labor, energy, and other direct cost of goods sold.
(2)Advanced production credit related to Section 45X of the Inflation Reduction Act.
(3)Includes freight costs and FIFO inventory adjustment.
(4)Includes equity in losses or earnings from joint ventures and inventory revaluation to lower of cost or net realizable value.
v3.25.0.1
Derivatives
 12 Months Ended
Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Derivatives Derivatives
As of December 31, 2024, we had an open position of 32,000 tonnes related to LME forward financial sales contracts to fix the forward LME aluminum price and an open position of 32,000 tonnes related to MWP forward financial sales contracts to fix the forward MWP price. These contracts are expected to settle monthly through September 2026. We also enter into financial contracts with various counterparties to offset fixed price sales arrangements with certain of our customers ("fixed for floating swaps") to remain exposed to the LME and MWP aluminum prices. As of December 31, 2024, we had no open fixed for floating swaps.
We previously entered into forward contracts to hedge the risk of fluctuations associated with the Icelandic Krona (ISK) and Euro for contracts related to the construction of the Grundartangi casthouse and the Sebree casthouse project denominated in these currencies ("casthouse currency hedges"). As of December 31, 2024, we had no open casthouse currency hedges.
We previously entered into financial contracts to hedge a portion of our exposure at our operations to the NYMEX Henry Hub (“NYMEX Henry Hub natural gas price swaps”). The natural gas volume is measured per million British Thermal Units ("MMBtu"). As of December 31, 2024, we had no open NYMEX Henry Hub natural gas price swaps.
We have entered into financial contracts to hedge a portion of our exposure at our operations to Heavy Fuel Oil (“HFO price swaps”). The HFO volume is measured per barrel. As of December 31, 2024, we had an open position of 295,000 barrels. The HFO price swaps are expected to settle monthly through December 2025.
We have entered into financial contracts to fix a portion of our exposure to the Indiana Hub power market at our Sebree plant ("Indiana Hub power price swaps"). As of December 31, 2024, we had an open position of 591,192 MWh. The Indiana Hub power price swaps are expected to settle monthly through September 2026.
Our agreements with derivative counterparties contain certain provisions requiring collateral to be posted in the event the market value of our position exceeds the margin threshold limit of our master agreement with the counterparty. As of December 31, 2024 and December 31, 2023, the Company had not recorded restricted cash as collateral related to open derivative contracts under the master arrangements with our counterparties.
The following table sets forth the Company's derivative assets and liabilities that were accounted for at fair value and not designated as cash flow hedges as of December 31, 2024 and 2023, respectively:
Asset Fair Value
20242023
Commodity contracts (1)
$4.5 $2.9 
Foreign exchange contracts (2)
— — 
Total$4.5 $2.9 
 Liability Fair Value
20242023
Commodity contracts (1)
4.4 7.8 
Foreign exchange contracts (2)
— 0.1 
Total$4.4 $7.9 
(1)Commodity contracts reflect our outstanding LME and MWP forward financial sales contracts, fixed for floating swaps, HFO price swaps and Indiana Hub power price swaps. At December 31, 2024, $0.0 million of Due to affiliates was related to commodity contract liabilities with Glencore. At December 31, 2023, $6.4 million of Due to affiliates was related to commodity contract liabilities with Glencore.
(2)Foreign exchange contracts reflect our outstanding FX swaps and casthouse currency hedges.
The following table summarizes the net gain (loss) on forward and derivative contracts for the years ended December 31, 2024, 2023, and 2022:
Year Ended December 31,
202420232022
Commodity contracts (1)
$2.1 $63.5 $206.6 
Foreign exchange contracts(0.1)(1.7)(9.4)
   Total$2.0 $61.8 $197.2 
(1)For the years ended December 31, 2024, 2023, and 2022, $(0.5) million, $0.6 million, and $(13.3) million of net gain (loss), respectively, was with Glencore.
v3.25.0.1
Variable Interest Entity
 12 Months Ended
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Variable Interest Entity Variable Interest Entity
The Company consolidates Jamalco, a bauxite mining and alumina refinery in Jamaica, under the variable interest entity ("VIE") model. The Company's wholly-owned subsidiary, General Alumina Jamaica Limited, is the managing partner of the Jamalco joint venture. Jamalco lacks sufficient equity investment at risk in accordance with relevant guidance. Based on its purpose and design, Jamalco is expected to require additional subordinated financial support, such as those in the form of equity contributions or other forms of subordinated financing, which the Company expects would require parent guarantees. To that end, the Company made an immediate equity contribution to Jamalco upon acquisition, and has provided subsequent financing of costs for Jamalco to perform its activities in the ordinary course of business. Jamalco was designed in order to distribute operations risk related to the mining and alumina refining operations, as well as commodity price risk.
Although our partner has certain participating rights over some decisions of the entity, the Company has power over the majority of key activities at Jamalco that significantly affect its economic performance over which the counterparty does not have such participating rights; therefore, the Company is the primary beneficiary of the VIE.
The table below shows the carrying amounts and classification of the consolidated VIE's assets and liabilities included in the Consolidated Balance Sheets as of December 31, 2024 and 2023.
December 31,
20242023
ASSETS
Cash and cash equivalents17.4 7.4 
Accounts receivable - net1.1 — 
Non-trade receivables13.1 38.3 
Due from affiliates75.1 76.7 
Inventories109.8 96.6 
Prepaid and other current assets2.0 8.7 
Total current assets218.5 227.7 
Property, plant and equipment - net232.1 248.7 
Other assets23.1 27.1 
TOTAL473.7 503.5 
LIABILITIES
LIABILITIES:
Accounts payable, trade39.1 73.1 
Accrued compensation and benefits8.5 2.3 
Due to affiliates49.6 55.4 
Accrued and other current liabilities7.2 7.1 
Total current liabilities104.4 137.9 
Accrued benefits costs - less current portion17.7 0.8 
Other liabilities66.7 36.1 
Asset retirement obligations - less current portion35.0 26.0 
Total noncurrent liabilities119.4 62.9 
TOTAL
223.8 200.8 
v3.25.0.1
Pay vs Performance Disclosure - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pay vs Performance Disclosure      
Net income attributable to Century stockholders $ 336.8 $ (43.1) $ (14.1)
v3.25.0.1
Insider Trading Arrangements
 3 Months Ended
Dec. 31, 2024
Trading Arrangements, by Individual  
Rule 10b5-1 Arrangement Adopted false
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
v3.25.0.1
Insider Trading Policies and Procedures
 12 Months Ended
Dec. 31, 2024
Insider Trading Policies and Procedures [Line Items]  
Insider Trading Policies and Procedures Adopted true
v3.25.0.1
Cybersecurity Risk Management and Strategy Disclosure
 12 Months Ended
Dec. 31, 2024
Cybersecurity Risk Management, Strategy, and Governance [Line Items]  
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]
Century recognizes the importance of developing, implementing, and maintaining appropriate cybersecurity measures to safeguard our information systems and protect the confidentiality, integrity, and availability of our data. The Board is actively involved in oversight of Century’s risk management program, and cybersecurity represents an important component of Century’s overall approach to enterprise risk management (“ERM”). Century’s cybersecurity policies, standards, processes and practices are based on recognized security frameworks and applicable industry standards. In general, Century seeks to address cybersecurity risks through a comprehensive approach that is focused on preserving the confidentiality, security and availability of the information that Century generates, collects and stores by identifying, preventing and mitigating cybersecurity threats and effectively responding to cybersecurity incidents when they occur.
As one of the critical elements of the Company’s overall ERM approach, the Company’s cybersecurity program is focused on the following key areas:
•Governance: As discussed in more detail under the heading “Governance,” the Board’s oversight of cybersecurity risk management is supported by the Company’s Chief Information Officer, other members of Management and a dedicated Cybersecurity team.
•Collaborative Approach: The Company has implemented a comprehensive approach to identifying, preventing and mitigating cybersecurity threats and incidents, while also implementing controls and procedures that provide for the prompt escalation of certain cybersecurity incidents so that decisions regarding the public disclosure and reporting of such incidents can be made by management in a timely manner.
•Technical Safeguards: The Company deploys technical safeguards that are designed to protect the Company’s information systems from cybersecurity threats, including firewalls, intrusion prevention and detection systems, logical access controls, and endpoint protection, which are evaluated and improved through vulnerability assessments and cybersecurity threat intelligence.
•Incident Response and Recovery Planning: The Company has established and maintains incident response and recovery plans that address the Company’s response to a cybersecurity incident.
•Third-Party Risk Management: The Company maintains a risk-based approach to identifying and overseeing cybersecurity risks presented by third parties, including vendors, service providers and other external users of the Company’s systems, as well as the systems of third parties that could adversely impact our business in the event of a cybersecurity incident affecting those third-party systems.
•Network Penetration Testing: The Company performs an internal and external network penetration test led by its Internal Audit team and addresses any findings in a timely manner.
Cybersecurity Risk Management Processes Integrated [Flag] true
Cybersecurity Risk Management Processes Integrated [Text Block]
Century recognizes the importance of developing, implementing, and maintaining appropriate cybersecurity measures to safeguard our information systems and protect the confidentiality, integrity, and availability of our data. The Board is actively involved in oversight of Century’s risk management program, and cybersecurity represents an important component of Century’s overall approach to enterprise risk management (“ERM”). Century’s cybersecurity policies, standards, processes and practices are based on recognized security frameworks and applicable industry standards. In general, Century seeks to address cybersecurity risks through a comprehensive approach that is focused on preserving the confidentiality, security and availability of the information that Century generates, collects and stores by identifying, preventing and mitigating cybersecurity threats and effectively responding to cybersecurity incidents when they occur.
Cybersecurity Risk Management Third Party Engaged [Flag] true
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag] true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag] false
Cybersecurity Risk Board of Directors Oversight [Text Block]
The Board as a whole also oversees the Company’s cybersecurity risks. Our Chief Information Officer updates the Board periodically regarding the actions management is taking to mitigate the Company’s cybersecurity risks and enhance the Company’s cybersecurity protection. Management routinely evaluates the Company’s existing security processes, procedures and systems in order to determine whether additional enhancements are needed to further reduce the likelihood and impact of a future cybersecurity event. Some of the Company’s current safeguards include multi-factor authentication for remote access to systems; performing email phishing test campaigns; email spam filtering; restricted internet firewall rules; limiting memory stick and external hard drive use; requiring timely application of security and software patches on servers; antivirus endpoint protection; performing 24-hour/7-day a week network monitoring; and improving our backup and recovery strategy, among others.
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block] The Chief Information Officer, as well as other members of Management, plays a pivotal role in informing the Board on cybersecurity risks by providing comprehensive briefings to the Board on a regular basis.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]
The Chief Information Officer, as well as other members of Management, plays a pivotal role in informing the Board on cybersecurity risks by providing comprehensive briefings to the Board on a regular basis. These briefings encompass a broad range of topics, including:
•Current cybersecurity landscape and emerging threats;
•Status of ongoing cybersecurity initiatives and strategies;
•Overall security posture and layers of defense;
•Incident reports and learnings from any cybersecurity events; and
•Compliance with regulatory requirements and industry standards.
In addition to regularly scheduled meetings, the Board and the Chief Information Officer maintain an ongoing dialogue regarding emerging or potential cybersecurity risks.
Cybersecurity Risk Role of Management [Text Block]
The Chief Information Officer, as well as other members of Management, plays a pivotal role in informing the Board on cybersecurity risks by providing comprehensive briefings to the Board on a regular basis. These briefings encompass a broad range of topics, including:
•Current cybersecurity landscape and emerging threats;
•Status of ongoing cybersecurity initiatives and strategies;
•Overall security posture and layers of defense;
•Incident reports and learnings from any cybersecurity events; and
•Compliance with regulatory requirements and industry standards.
In addition to regularly scheduled meetings, the Board and the Chief Information Officer maintain an ongoing dialogue regarding emerging or potential cybersecurity risks. Together, they receive updates on any significant developments in the cybersecurity domain, ensuring the Board’s oversight is proactive and responsive. The Board actively participates in strategic decisions related to cybersecurity, offering guidance and approval for major initiatives. This involvement ensures that cybersecurity considerations are integrated into the broader strategic objectives of the Company. The Board conducts an annual review of the company’s cybersecurity posture and the effectiveness of its risk management strategies. This review helps in identifying areas for improvement and ensuring the alignment of cybersecurity efforts with the overall risk management framework.
Cybersecurity Risk Management Positions or Committees Responsible [Flag] true
Cybersecurity Risk Management Positions or Committees Responsible [Text Block] The Chief Information Officer, as well as other members of Management, plays a pivotal role in informing the Board on cybersecurity risks by providing comprehensive briefings to the Board on a regular basis.
Cybersecurity Risk Management Expertise of Management Responsible [Text Block] The Chief Information Officer has extensive experience working in and leading the Company's information systems.
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]
The Chief Information Officer is continually informed about the latest developments in cybersecurity, including potential threats and innovative risk management techniques. This ongoing knowledge acquisition is crucial for the effective prevention, detection, mitigation, and remediation of cybersecurity incidents. The Chief Information Officer implements and oversees processes for the regular monitoring of our information systems. This includes the deployment of advanced security measures and regular system audits to identify potential vulnerabilities. In the event of a cybersecurity incident, the CIO is equipped with a well-defined incident response plan. This plan includes immediate actions to mitigate the impact and long-term strategies for remediation and prevention of future incidents.
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag] true
v3.25.0.1
Summary of Significant Accounting Policies (Policies)
 12 Months Ended
Dec. 31, 2024
Accounting Policies [Abstract]  
Basis of Presentation Basis of Presentation — The consolidated financial statements include the accounts of Century Aluminum Company and our subsidiaries, after elimination of all intercompany transactions and accounts.
Variable Interest Entities
Variable Interest Entities - We evaluate arrangements and contracts with other entities to determine if they are VIEs and if we are the primary beneficiary. GAAP provides a framework for identifying VIEs and determining when a company should include the assets, liabilities, non-controlling interest, and results of activities of a VIE in its consolidated financial statements.
A VIE should be consolidated if a party with an ownership, contractual or other financial interest in the VIE (a variable interest holder) has the power to direct the VIE’s most significant activities and the obligation to absorb losses or right to receive benefits of the VIE that could be significant to the VIE. A variable interest holder that consolidates the VIE is called the primary beneficiary. Upon consolidation, the primary beneficiary generally must initially record all of the VIE’s assets, liabilities, and non-controlling interests at fair value and subsequently account for the VIE as if it were consolidated.
Our evaluation of whether our interest qualifies as the primary beneficiary of a VIE involves significant judgments, estimates and assumptions and includes a qualitative analysis of the activities that most significantly impact the VIE’s economic performance and whether the Company has the power to direct those activities, the design of the entity, the rights of the parties and the purpose of the arrangement. Jamalco is a VIE. See Note 21. Variable Interest Entity.
Revenue recognition
Revenue recognition — See Note 5. Revenue.
We enter into contracts to sell mainly primary aluminum to our customers. Revenue is recognized when our performance obligations with our customers are satisfied. Our obligations under the contracts are satisfied when we transfer control of our primary aluminum to our customers which is generally upon shipment or delivery to customer directed locations. The amount of consideration we receive, thus the revenue we recognize, is a function of volume delivered, market price of primary aluminum, which is based on the LME, plus regional premiums and any value-added product premiums or alumina which is based on the alumina pricing index, plus Atlantic differential.
The payment terms and conditions in our contracts vary and are not significant to our revenue. We complete an appropriate credit evaluation for each customer at contract inception. Customer payments are due in arrears and are recognized as accounts receivable - net and due from affiliates in our Consolidated Balance Sheets.
In connection with our sales agreements with certain customers, including Glencore, we invoice the customer prior to physical shipment of goods for a majority of production generated from each of our U.S. domestic smelters. For those sales, revenue is recognized only when the customer has specifically requested such treatment and has made a commitment to purchase the product. The goods must be complete, ready for shipment and separated from other inventory with control over the goods passing to the customer. We must retain no further performance obligations.
Cash and Cash Equivalents
Cash and Cash Equivalents — Cash and cash equivalents are comprised of cash, money market funds and short-term investments having original maturities of three months or less. The carrying amount of cash equivalents approximates fair value.
Accounts Receivable and Due from Affiliates
Accounts Receivable and Due from Affiliates — These amounts are net of an allowance for expected losses of $0.5 million at both December 31, 2024 and 2023.
Inventories
Inventories — Our inventories are stated at the lower of cost or net realizable value, using the first-in, first-out ("FIFO") and the weighted average cost method. Due to the nature of our business, our inventory values are subject to market price changes and these changes can have a significant impact on cost of goods sold and gross profit in any period. Reductions in net realizable value below cost basis at the end of a period will have an impact on our cost of goods sold as this inventory is sold in subsequent periods.
Property, Plant and Equipment
Property, Plant and Equipment — Property, plant and equipment is stated at cost. Additions and improvements are capitalized when each asset is placed into service. Asset and accumulated depreciation accounts are relieved for dispositions with resulting gains or losses included in Other income (loss) - net. Maintenance and repairs are expensed as incurred. Depreciation of plant and equipment is provided for by the straight-line method over the following estimated useful lives:
Building and improvements    10 to 45 years
Machinery and equipment    5 to 35 years
Technology and software    3 to 7 years
The Company incurs deferred costs during the development stage of a mine life cycle. Such costs include the construction of access and haul roads, detailed drilling and geological analysis to further define the grade and quality of the known bauxite, and overburden removal costs. These costs relate to sections of the related mines where the Company is currently extracting bauxite or preparing for production in the near term. These sections are outlined and planned incrementally and generally are mined over periods outlined in the Company's mine plans. The amount of geological drilling and testing necessary to determine the economic viability of the bauxite deposit being mined is such that the resources are considered to be proved mineral reserves. Mineral reserves are amortized on a units-of-production basis.
Impairment of long-lived assets
Impairment of long-lived assets — The Company reviews property, plant and equipment ("long-lived assets") for impairment whenever events or changes in circumstances, known as triggering events, indicate that the carrying amount of a long-lived asset or an asset group may not be recoverable. Management considers various factors when determining if long-lived assets should be evaluated for impairment, including a significant adverse change in the business climate or industry conditions (such as sustained decreases in commodity prices, volatility in energy costs, and the global economy), a current period operating or cash flow loss combined with a history of losses, a significant adverse change in the extent or manner in which an asset is used or a current expectation that the asset will be sold or otherwise disposed of before the end of its useful life. If a triggering event is identified, the Company determines if the long-lived asset or asset group is recoverable. Recoverability is measured by comparison of the carrying amount of a long-lived asset or asset group held and used to estimate undiscounted future net cash flows expected to be generated by the long-lived asset or asset group. Impairment evaluation and fair value is based on estimates and assumptions that take into account our business plans and a long-term investment horizon, including consideration of commodity pricing, energy costs and other global economic conditions which may have an adverse effect on recoverability. If deemed unrecoverable, an impairment loss would be recognized for the amount by which the carrying amount exceeds the estimated fair value of the long-lived asset or asset group.
Leases
Leases — We determine whether an arrangement is a lease at the inception of the arrangement based on the terms and conditions in the contract. A contract contains a lease if there is an identified asset which we have the right to control. We have made a policy election not to separate lease and non-lease components within contracts. We have also elected not to recognize the impact of short term leases in the right of use asset ("ROUA") and right of use liability ("ROUL") balances. Short term leases are leases that have a lease term less than one year and do not include a purchase option.
Income Taxes
Income Taxes — We account for income taxes using the asset and liability method, whereby deferred income taxes reflect the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. In evaluating our ability to realize deferred tax assets, we use judgment to determine if it is more likely than not that some portion or all of a deferred tax asset will not be realized, and if a corresponding valuation allowance is required.
Defined Benefit Pension and Other Postretirement Benefits
Defined Benefit Pension and Other Postretirement Benefits — We sponsor defined benefit pension and OPEB plans for certain of our domestic hourly and salaried employees and a supplemental executive retirement benefit plan for certain current and former executive officers. Plan assets and obligations are measured annually or more frequently if there is a re-measurement event, based on the Company’s measurement date utilizing various actuarial assumptions. We attribute the service costs for the plans over the working lives of plan participants. The effects of actual results differing from our assumptions and the effects of changing assumptions are considered actuarial gains or losses. Actuarial gains or losses are recorded in Accumulated Other Comprehensive Income (Loss).
We contribute to our defined benefit pension plans based upon actuarial and economic assumptions designed to achieve adequate funding of the projected benefit obligations and to meet the minimum funding requirements.
Postemployment Benefits
Postemployment Benefits — We provide certain postemployment benefits to certain former and inactive employees and their dependents during the period following employment, but before retirement. These benefits include salary continuance, supplemental unemployment and disability health care. We recognize the estimated future cost of providing postemployment benefits on an accrual basis over the active service life of the employee.
Derivatives and Hedging
Derivatives and Hedging — As a global producer of primary aluminum, our operating results and cash flows from operations are subject to risk of fluctuations in the market prices of primary aluminum. We may from time to time enter into financial contracts to manage our exposure to such risk. Derivative instruments may consist of variable to fixed financial contracts and back-to-back fixed to floating arrangements for a portion of our sale of primary aluminum, where we receive fixed and pay floating prices from our customers and to counterparties, respectively.
From time to time, we may manage our exposure to fluctuations in the market price of power through financial instruments designed to protect our downside risk exposure. We are also exposed to foreign currency risk, and we may manage our exposure by entering into foreign currency forward contracts or option contracts for forecasted transactions and projected cash flows for foreign currencies in future periods.
Our derivatives are not designated as cash flow hedges.
Derivative and hedging instruments are recorded in due from affiliates, derivative assets, other assets, due to affiliates, derivative liabilities and derivative liabilities - less current portion in the Consolidated Balance Sheets at fair value. We value our derivative and hedging instruments using quoted market prices and other significant unobservable inputs.
We recognize changes in fair value and settlements of derivative instruments in net gain (loss) on forward and derivative contracts in the Consolidated Statements of Operations as they occur.
Foreign Currency Foreign Currency – We are exposed to foreign currency risk due to fluctuations in the value of the U.S. dollar as compared to the Euro and the Icelandic krona ("ISK"), and the Chinese renminbi. Grundartangi, Vlissingen and Jamalco use the U.S. dollar as their functional currency, as contracts for sales of aluminum and alumina and purchases of alumina and power are denominated in U.S. dollars. Transactions denominated in currencies other than the functional currency are recorded based on exchange rates at the time such transactions arise and any transaction gains and losses are reflected in Other income (loss) - net in the Consolidated Statements of Operations.
Financial Instruments
Financial Instruments — Receivables, certain life insurance policies, payables, borrowings under revolving credit facilities and debt related to industrial revenue bonds ("IRBs") are carried at amounts that approximate fair value.
Earnings per share
Earnings per share — Basic earnings (loss) per share ("EPS") amounts are calculated by dividing earnings (loss) available to common stockholders by the weighted average number of common shares outstanding using the two-class method. Under the two-class method, net income is allocated between shares of common stock and other participating securities based on their participating rights. Net loss is not allocated to other participating securities if they are not obligated to share in the losses based on their contractual terms. Diluted earnings per share is calculated by dividing net income attributable to common shareholders by the weighted average number of common and dilutive common equivalent shares outstanding during the period. Common equivalent shares are not included in the denominator of the diluted loss per share calculation when inclusion of such shares would be anti-dilutive.
The dilutive effect to earnings per share is determined using the "if converted" method whereby, if the conversion of the convertible notes would be dilutive, interest expense on the outstanding notes is added back to the diluted earnings numerator and all of the potentially dilutive shares are included in the diluted common shares outstanding denominator for the computation of diluted earnings per share.
Our Series A Convertible Preferred Stock is a non-cumulative perpetual participating convertible preferred stock with no set dividend preferences. In periods where we report net losses, we do not allocate these losses to the Convertible Preferred Stock for the computation of basic or diluted EPS.
Asset Retirement Obligations
Asset Retirement Obligations — We are subject to environmental regulations which create certain legal obligations related to the normal operations of our bauxite mine and alumina refinery and our domestic primary aluminum smelter operations. Our asset retirement obligations ("AROs") consist primarily of costs associated with mine reclamation obligations, closure of bauxite residue areas, landfill closure, and the disposal of spent potliner used in the reduction cells of our domestic smelters. AROs are recorded on a discounted basis at the time the obligation is incurred (when the potliner is put in service or upon disturbance of lands to be mined) and accreted over time for the change in the present value of the liability. We capitalize the asset retirement costs by increasing the carrying amount of the related long-lived assets and depreciating these assets over their remaining useful lives.
Certain conditional asset retirement obligations ("CAROs") related to the remediation of our primary aluminum facilities for hazardous material, such as landfill materials and asbestos, have not been recorded because they have an indeterminate settlement date. CAROs are a legal obligation to perform an asset retirement activity in which the timing and/or method of settlement are conditional on a future event that may or may not be within our control.
Concentrations of Credit Risk
Concentrations of Credit Risk — Financial instruments, which potentially expose us to concentrations of credit risk, consist principally of trade receivables. Our limited customer base increases our concentrations of credit risk with respect to trade receivables. We routinely assess the financial strength of our customers and collectability of our trade receivables and recognize an allowance based on our estimate of lifetime expected credit losses in accordance with the current expected credit loss ("CECL") model.
Share-Based Compensation
Share-Based Compensation — We measure the cost of employee services received in exchange for an award of equity instruments based on the fair value of the award on the grant date. We recognize the cost over the period during which an employee is required to provide service in exchange for the award. We issue shares to satisfy the requirements of our share-based compensation plans. At this time, we do not plan to issue treasury shares to support our share-based compensation plans, but we may in the future. We award performance units to certain officers and employees. The performance units may be settled in cash or common stock at the discretion of the Board. We have not issued any stock options since 2009.
Recent accounting pronouncements
Recent accounting pronouncements
In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, that requires disclosure of significant segment expenses that are regularly reviewed by the chief operating decision maker and included within each reported measure of segment profit or loss. The standard also requires disclosure of the composition of other segment items included in the measure of segment profit or loss that are not separately disclosed. The new standard is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We adopted this accounting standard for our fiscal year beginning January 1, 2024, retrospectively. Therefore, prior periods have been updated to conform with the current period presentation. See Note 19. Business Segments for our reportable segment disclosures.
In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, that requires presentation of specific categories of reconciling items, as well as reconciling items that meet a quantitative threshold, in the reconciliation between the income tax provision and the income tax provision using statutory tax rates. The standard also requires disclosure of income taxes paid disaggregated by jurisdiction with separate disclosure of income taxes paid to individual jurisdictions that meet a quantitative threshold. The amendments in this accounting standard are effective for fiscal years beginning after December 15, 2024, on a prospective basis. Early adoption and retrospective application are permitted. We do not expect the adoption of this accounting standard to have an impact on our consolidated financial statements, but will require certain additional disclosures. The Company plans to adopt this guidance on its consolidated financial statements and related disclosures for the annual period ending December 31, 2025.
In November 2024, the FASB issued ASU 2024-03, Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, that requires disclosure of the amounts of purchases of inventory, employee compensation, depreciation, and intangible asset amortization included in each relevant expense line item on the income statement. The standard also requires a qualitative description of other amounts included in each relevant expense line item on the income statement that are not separately disclosed. In addition, entities are required to disclose the nature and amount of selling expenses. The new standard is effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027. Early adoption is permitted. We do not expect any impact to the consolidated financial statements, but the standard will require certain additional disclosures in the notes to the consolidated financial statements and the Company plans to adopt this guidance for the annual period ending December 31, 2027.
v3.25.0.1
Acquisition of Jamalco (Tables)
 12 Months Ended
Dec. 31, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]  
Schedule of fair value of assets acquired and liabilities assumed
The following table summarizes the estimated fair value of identified assets acquired, liabilities assumed and noncontrolling interest at the date of acquisition:
Purchase price allocationAmount
Identifiable assets acquired and liabilities assumed
Cash and cash equivalents$19.4 
Restricted cash8.3 
Accounts receivable - net7.7 
Non-trade receivables40.4 
Inventories103.9 
Prepaid and other current assets4.2 
Property, plant and equipment217.2 
Other assets26.1 
Accounts payable, trade(94.6)
Accrued and other current liabilities(29.5)
Other liabilities(36.5)
Asset retirement obligations(23.9)
Total identifiable assets acquired and liabilities assumed242.7 
Less: noncontrolling interest (3.2)
Bargain purchase gain245.9 
Schedule of unaudited pro forma financial information
The following unaudited pro forma financial information reflects the results of operations of the Company for the twelve months ended December 31, 2023 and 2022, respectively, as if the acquisition of Jamalco had been completed on January 1, 2022. This unaudited pro forma financial information has been prepared for informational purposes and is not necessarily indicative of the actual consolidated results of operations had the acquisition been completed on January 1, 2022, nor is the information indicative of future results of operations of the combined companies.
Year Ended December 31,
20232022
Revenue
$2,235.1 $2,831.0 
Earnings
$(45.9)$(33.1)
v3.25.0.1
Related Party Transactions (Tables)
 12 Months Ended
Dec. 31, 2024
Related Party Transactions [Abstract]  
Schedule of related party transactions
A summary of the aforementioned significant related party sales and purchases for the years ended December 31, 2024, 2023 and 2022 is as follows:
 Year Ended December 31,
 202420232022
Net sales to Glencore$1,312.1 $1,612.1 $1,671.1 
Purchases from Glencore (1)
277.9 181.4 284.7 
(1)Includes settlements of financial contract positions.
v3.25.0.1
Revenue (Table)
 12 Months Ended
Dec. 31, 2024
Revenue from Contract with Customer [Abstract]  
Schedule of disaggregation of revenue
We disaggregate our revenue by geographical region as follows:
Year ended December 31,
Net Sales202420232022
United States$1,427.0 $1,358.6 $1,737.2 
Iceland793.3 826.8 1,040.1 
Total$2,220.3 $2,185.4 $2,777.3 
The table below shows the amount of net sales to external customers for each of the Company's product categories which accounted for 10% or more of consolidated net sales in either period for the years ended December 31, 2024, 2023 and 2022.
Year ended December 31,
Net Sales202420232022
Aluminum$1,882.1 $1,972.6 $2,750.3 
Alumina338.2 212.8 27.0 
Total$2,220.3 $2,185.4 $2,777.3 
v3.25.0.1
Leases (Tables)
 12 Months Ended
Dec. 31, 2024
Leases [Abstract]  
Schedule of assets and liabilities, lessee
Our ROUA and ROUL balances for the years ended December 31, 2024 and December 31, 2023 were as follows (in millions):
December 31,
20242023
ROUA(1)
$21.0 $24.7 
ROUL - current(2)
$3.0 $2.3 
ROUL - non-current(3)
18.7 21.9 
Total ROUL$21.7 $24.2 
(1)ROUA was recorded as part of Other Assets within Non-current assets at December 31, 2024 and 2023.
(2)ROUL - current was recorded as part of Accrued and other current liabilities within Current liabilities at December 31, 2024 and 2023.
(3)ROUL - non-current was recorded as part of Other liabilities within Non-current liabilities at December 31, 2024 and 2023.
Schedule of maturities of operating lease liability balances
The undiscounted maturities of our operating lease liability balances as of December 31, 2024 are as follows (in millions):
Year
2025$3.9 
20263.3 
20272.8 
20282.8 
20292.7 
Thereafter16.2 
Total 31.7 
Less: Interest(10.0)
ROUL$21.7 
Schedule of lease, expense
Total operating expense includes the following (in millions):
December 31,
20242023
Operating leases expense$5.3 $4.9 
Short term lease expense3.2 0.6 
Total(1)
$8.5 $5.5 
(1)Total lease expense is included in cost of goods sold and selling, general, and administrative expenses on the Consolidated Statements of Operations.
v3.25.0.1
Fair Value Measurements (Tables)
 12 Months Ended
Dec. 31, 2024
Fair Value Disclosures [Abstract]  
Schedule of financial assets and liabilities at fair value on a recurring basis
Recurring Fair Value Measurements
As of December 31, 2024
Level 1Level 2Level 3Total
ASSETS:    
Cash equivalents$7.9 $— $— $7.9 
Trust assets (1)
0.3— — 0.3
Derivative instruments— 4.5 — 4.5 
TOTAL$8.2 $4.5 $— $12.7 
LIABILITIES:    
Derivative instruments— 4.4 — 4.4 
TOTAL$— $4.4 $— $4.4 
Recurring Fair Value Measurements
As of December 31, 2023
Level 1Level 2Level 3Total
ASSETS:    
Cash equivalents$16.8 $— $— $16.8 
Trust assets (1)
0.2— — 0.2 
Derivative instruments— 2.9 — 2.9 
TOTAL$17.0 $2.9 $— $19.9 
LIABILITIES:    
Derivative instruments— 7.9 — 7.9 
TOTAL$— $7.9 $— $7.9 
(1)Trust assets are currently invested in money market funds. These trust assets are held to fund the non-qualified supplemental executive pension benefit obligations for certain of our officers.
Schedule of valuation methodology for assets and liabilities at fair value
The following section describes the valuation techniques and inputs used for fair value measurements categorized within Level 2 of the fair value hierarchy:
Level 2 Fair Value Measurements:
Asset / LiabilityValuation TechniquesInputs
LME forward financial sales contractsDiscounted cash flowsQuoted LME forward market, Secured Overnight Financing Rate ("SOFR") discount rate
Midwest Premium ("MWP") forward financial sales contractsDiscounted cash flowsQuoted MWP forward market, SOFR discount rate
Fixed for floating swapsDiscounted cash flowsQuoted LME forward market, quoted MWP forward market
Indiana Hub power price swapsDiscounted cash flowsQuoted Indiana Hub forward market, SOFR discount rate
FX swaps Discounted cash flowsEuro/USD forward exchange rate
Casthouse currency hedgesDiscounted cash flowsEuro/USD forward exchange rate; ISK/USD forward exchange rate
Heavy Fuel Oil ("HFO") price swapsDiscounted cash flowsQuoted HFO forward market
Schedule of fair value reconciliation of Level 3 assets and liabilities measured at fair value
The following table presents the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis.
For the twelve months ended December 31, 2023 and 2024Level 3 AssetsLevel 3 Liabilities
LME forward financial sales contractsLME forward financial sales contracts
Balance as of January 1, 2023$1.8 $(4.6)
Transfers out of Level 3 (1)
(1.8)4.6 
Balance as of December 31, 2023$— $— 
Transactions during 2024$— $— 
Balance as of December 31, 2024$— $— 
Change in unrealized gains (losses) 2023 (2)
$— $— 
Change in unrealized gains (losses) 2024 (2)
$— $— 
(1)Transfer out of Level 3 due to period of time remaining in derivative contract.
(2)Gains and losses are presented in the Consolidated Statements of Operations within the line item "Net gain (loss) on forward and derivative contracts."
v3.25.0.1
Debt (Tables)
 12 Months Ended
Dec. 31, 2024
Debt Disclosure [Abstract]  
Schedule of debt
 December 31,
 20242023
Debt classified as current liabilities:  
Hancock County industrial revenue bonds ("IRBs") due April 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) (1)
$7.8 $7.8 
U.S. Revolving Credit Facility (2)
20.0 23.7 
Iceland Revolving Credit Facility (3)
34.0 — 
Grundartangi Casthouse Facility (4)
9.0 5.5 
Iceland Term Facility
— 1.3 
Vlissingen Facility Agreement (5)
— 10.0 
Debt classified as non-current liabilities:  
Grundartangi casthouse facility, net of financing fees of $0.0 million at December 31, 2024 (4)
114.2 98.8 
Vlissingen Facility Agreement (5)
10.0 — 
7.5% senior secured notes due April 1, 2028, net of financing fees of $1.9 million at December 31, 2024, interest payable semiannually
248.1 247.4 
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.2 million at December 31, 2024, interest payable semiannually
85.1 84.7 
Total$528.2 $479.2 
(1)The IRBs are classified as current liabilities because they are remarketed weekly and could be required to be repaid upon demand if there is a failed remarketing. The interest rate at December 31, 2024 was 3.75%.
(2)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at December 31, 2024 was 8.00%.
(3)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at December 31, 2024 was 7.84%.
(4)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at December 31, 2024 was 8.06%.
(5)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at December 31, 2024 was 7.99%
Schedule of debt redemption rights
Redemption Rights. Prior to April 1, 2024, we may redeem the 2028 Notes, in whole or in part, at a redemption price equal to 100.00% of the principal amount plus a make-whole premium and accrued and unpaid interest, and if redeemed during the twelve-month period beginning on April 1 of the years indicated below, at the following redemption prices plus accrued and unpaid interest:
YearPercentage
2024103.750%
2025101.875%
2026 and Thereafter100.000%
Schedule of line of credit facilities
Status of our U.S. revolving credit facility:
December 31, 2024
Credit facility maximum amount$250.0 
Borrowing availability149.3 
Outstanding letters of credit issued63.7 
Outstanding borrowings20.0 
Borrowing availability, net of outstanding letters of credit and borrowings65.6 
Status of our Iceland revolving credit facility:
December 31, 2024
Credit facility maximum amount$100.0 
Borrowing availability100.0 
Outstanding letters of credit issued— 
Outstanding borrowings34.0 
Borrowing availability, net of outstanding letters of credit and borrowings66.0 
v3.25.0.1
Inventories (Tables)
 12 Months Ended
Dec. 31, 2024
Inventory, Net [Abstract]  
Schedule of inventories
Inventories, at December 31, consist of the following:
 20242023
Raw materials$180.8 $162.5 
Work-in-process52.1 42.9 
Finished goods74.6 46.3 
Operating and other supplies231.5 225.3 
Inventories$539.0 $477.0 
v3.25.0.1
Property, Plant and Equipment (Tables)
 12 Months Ended
Dec. 31, 2024
Property, Plant and Equipment [Abstract]  
Summary of property, plant and equipment
Property, plant and equipment, at December 31, consist of the following:
 20242023
Land and improvements$104.3 $105.1 
Mineral Reserves34.7 35.8 
Buildings and improvements404.3 328.8 
Machinery and equipment1,664.0 1,580.7 
Asset Retirement Obligation35.3 21.8 
Construction in progress44.7 160.3 
 2,287.3 2,232.5 
Less accumulated depreciation, amortization and depletion(1,309.0)(1,228.3)
Property, plant and equipment - net$978.3 $1,004.2 
v3.25.0.1
Accumulated Other Comprehensive Loss ("AOCL") (Tables)
 12 Months Ended
Dec. 31, 2024
Additional financial information disclosures [Abstract]  
Components of Accumulated Other Comprehensive Loss
Components of AOCL20242023
Defined benefit plan liabilities$(107.0)$(101.8)
Unrealized gain on financial instruments1.4 1.6 
Other comprehensive loss before income tax effect(105.6)(100.2)
Income tax effect(1)
2.3 2.3 
Accumulated other comprehensive loss$(103.3)$(97.9)
(1)The allocation of the income tax effect to the components of other comprehensive loss is as follows:
20242023
Defined benefit plan liabilities$2.6 $2.6 
Unrealized loss on financial instruments(0.3)(0.3)
The following table summarizes the changes in the accumulated balances for each component of AOCL:
Defined benefit plan and other postretirement liabilitiesUnrealized gain (loss) on financial instrumentsTotal, net of tax
Balance, December 31, 2021
$(84.0)$1.7 $(82.3)
Other comprehensive income (loss) before reclassifications(5.9)— (5.9)
Net amount reclassified to net income (loss)(5.7)(0.1)(5.8)
Balance, December 31, 2022
(95.6)1.6 (94.0)
Other comprehensive income (loss) before reclassifications(10.1)— (10.1)
Net amount reclassified to net income (loss)6.3 (0.1)6.2 
Balance, December 31, 2023
(99.4)1.5 (97.9)
Other comprehensive income (loss) before reclassifications(11.9)— (11.9)
Net amount reclassified to net income (loss)6.7 (0.2)6.5 
Balance, December 31, 2024
$(104.6)$1.3 $(103.3)
Reclassification out of AOCL
Reclassifications out of AOCL were included in the Consolidated Statements of Operations as follows:
Year Ended December 31,
AOCL ComponentsLocation202420232022
Defined benefit plan and other postretirement liabilitiesCost of goods sold$(8.5)$(1.0)$3.5 
Other income, net— — (8.9)
Selling, general and administrative expenses1.1 (0.2)3.3 
Other operating expense (income), net2.2 (2.6)(9.0)
Income tax expense— — (0.3)
Net of tax$(5.2)$(3.8)$(11.4)
Gain (loss) on financial instrumentsCost of goods sold$(0.2)$(0.1)$(0.2)
Income tax effect $— — (0.1)
Net of tax$(0.2)$(0.1)$(0.3)
v3.25.0.1
Pension and Other Postretirement Benefits (Tables)
 12 Months Ended
Dec. 31, 2024
Retirement Benefits [Abstract]  
Schedule of Changes in Projected Benefit Obligations
The change in benefit obligation and change in plan assets as of December 31 are as follows:
PensionOPEB
2024202320242023
Change in benefit obligation:    
Benefit obligation at beginning of year$305.1 $263.0 $76.8 $73.7 
Service cost4.0 3.3 0.2 0.1 
Interest cost17.2 17.3 3.9 3.9 
Plan amendments— 1.1 — — 
Actuarial (gain) loss(3.2)11.0 0.3 4.8 
Medicare Part D— — 0.2 0.3 
Acquisition— 28.6 — 0.8 
Benefits paid(21.4)(19.9)(5.7)(6.8)
Exchange rates(0.4)(0.5)— — 
Plan participants' contributions1.0 1.2 — — 
Benefit obligation at end of year$302.3 $305.1 $75.7 $76.8 
Schedule of Changes in Fair Value of Plan Assets
PensionOPEB
2024202320242023
Change in plan assets:    
Fair value of plan assets at beginning of year$256.8 $216.6 $— $— 
Actual return on plan assets6.8 21.4 — — 
Acquisition— 31.5 — — 
Employer contributions2.3 6.6 5.5 6.5 
Medicare Part D subsidy received— — 0.2 0.3 
Benefits paid(21.5)(19.9)(5.7)(6.8)
Exchange rates(0.3)(0.6)— — 
Plan participants' contributions1.0 1.2 — 
Fair value of assets at end of year$245.1 $256.8 $— $— 
Schedule of Amounts Recognized in Balance Sheet
 PensionOPEB
 2024202320242023
Funded status of plans:    
Funded status$(57.2)$(48.3)$(75.7)$(76.8)
Amounts recognized in the Consolidated Balance Sheets:
Current liabilities(1.8)(1.8)(6.5)(6.5)
Non-current liabilities(55.4)(46.5)(69.2)(70.3)
Net amount recognized$(57.2)$(48.3)$(75.7)$(76.8)
Amounts recognized in accumulated other comprehensive loss (pre-tax):  
Net loss$82.3 $82.1 $14.4 $14.8 
Prior service cost (benefit)1.6 1.8 — — 
Total$83.9 $83.9 $14.4 $14.8 
Schedule of Net Benefit Cost
Net Periodic Benefit Cost:
 Year Ended December 31,
 PensionOPEB
 202420232022202420232022
Service cost$4.0 $3.3 $4.3 $0.2 $0.1 $0.2 
Interest cost17.2 17.3 10.3 3.9 3.9 2.9 
Expected return on plan assets(18.3)(17.3)(23.5)— — — 
Amortization of prior service costs0.2 0.1 0.1 — — (1.3)
Amortization of net loss5.8 6.0 3.5 0.7 0.1 1.3 
Net periodic benefit cost8.9 9.4 (5.3)4.8 4.1 3.1 
Curtailment benefit (1)
— — — — — (8.9)
Total benefit cost$8.9 $9.4 $(5.3)$4.8 $4.1 $(5.8)
(1)During 2022, we re-measured certain other postretirement benefits triggered by the Hawesville smelter curtailment, leading to a non-cash OPEB curtailment benefit totaling $8.9 million for the year ended December 31, 2022.
Schedule of Amounts Recognized in Other Comprehensive Income (Loss)
Other changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (pre-tax):
 Year Ended December 31,
 PensionOPEB
 2024202320242023
Net (gain) loss$8.4 $6.9 $0.3 $4.8 
Net loss (gain) transferred due to acquisition— (4.5)— (0.2)
Prior service cost (benefit)— 1.2 — — 
Amortization of net loss, including recognition due to settlement(5.8)(6.0)(0.7)(0.2)
Amortization of prior service (cost) benefit, including curtailment(0.2)(0.1)— — 
Exchange rates(2.4)(1.1)— (0.1)
Total amount recognized in other comprehensive income (loss)
— (3.6)(0.4)4.3 
Net periodic benefit cost8.9 9.4 4.8 4.1 
Total recognized in net periodic benefit cost and other comprehensive income (loss)
$8.9 $5.8 $4.4 $8.4 
Schedule of Weighted Average Assumptions Used in Calculating Benefit Obligation and Net Periodic Benefit Cost
Weighted average assumptions used to determine benefit obligations at December 31:
PensionOPEB
2024202320242023
Discount rate (1)
5.99%5.19%5.62%5.19%
Rate of compensation increase without Jamaica3.0%3.5%3.0%3.5%
Rate of compensation increase Jamaica7.0%n/a7.0%n/a
Measurement date12/31/202412/31/202312/31/202412/31/2023
Weighted average assumptions used to determine net periodic benefit cost for the years ended December 31:
 PensionOPEB
 202420232022202420232022
Measurement date12/31/202312/31/202212/31/202112/31/202312/31/202212/31/2021
Fiscal year end12/31/202412/31/202312/31/202212/31/202412/31/202312/31/2022
Discount rate (1)
6.75%5.50%2.94%5.43%5.57%2.64%
Rate of compensation increase without Jamaica (2)
3.5%
4%/3.5%
3%/3.5%
3.5%
4%/3.5%
3%/3.5%
Rate of compensation increase Jamaica9.0%n/an/a8.0%n/an/a
Expected return on plan assets (3)
7.28%7.25%7.25%—%—%—%
(1)We use the Ryan Above Median Yield Curve to determine the discount rate.
(2)For 2024, the rate of compensation increase is 3.5%. For 2023, the rate of compensation increase was 4% per year for the first year and 3.5% per year thereafter. For 2022, the rate of compensation increase was 3% per year for the first year and 3.5% per year thereafter.
(3)The rate for each of our defined benefit plans was selected by taking into account our expected asset mix and is based on historical performance as well as expected future rates of return on plan assets.
Schedule of Allocation of Plan Assets The Pension Plans’ weighted average long-term strategic asset allocation policy targets are as follows:
 Pension Plan Asset Allocation
 2024 TargetDecember 31, 2024December 31, 2023
Return seeking assets:
Global equity50%51%44%
Diversified credit15%17%15%
Real assets10%11%10%
Liability hedging assets25%20%28%
Cash—%1%3%
 100%100%100%
Defined Benefit Plan, Plan Assets, Category
The following summarizes the Company’s Pension Plans' assets fair value by asset category:
As of December 31, 2024
Level 1Level 2Level 3Assets measured at NAVTotal
Cash and cash equivalents$0.7 $— $— $2.8 $3.5 
Global Equity20.0 — — 108.1 128.1 
Diversified Credit11.8 — — 35.3 47.1 
Real Assets— — — 23.1 23.1 
Liability hedging assets— — — 42.6 42.6 
Other
0.1 0.6 — — 0.7 
Total plan assets fair value$32.6 $0.6 $— $211.9 $245.1 
As of December 31, 2023
Cash and cash equivalents$0.4 $— $— $4.6 $5 
Global Equity19.7 — — 100.0 119.7 
Diversified Credit11.2 — — 34.7 45.9 
Real Assets— — — 22.8 22.8 
Liability hedging assets— — — 62.7 62.7 
Other
0.1 0.6 — — 0.7 
Total plan assets fair value$31.4 $0.6 $— $224.8 $256.8 
Schedule Of Expected Benefit Plan Contributions
We expect to make the following contributions for 2025:
2025
Expected pension plan contributions$8.0 
Expected OPEB benefits payments6.4 
Schedule of Expected Benefit Payments
The following table provides the estimated future benefit payments for the pension and other postretirement benefit plans:
 Pension BenefitsOPEB Benefits
2025$20.5 $6.5 
202620.9 6.5 
202720.9 6.5 
202821.4 6.7 
202921.7 6.5 
2030 – 203494.8 30.9 
Schedule of Multiemployer Plans
Century’s participation in the plan for the year ended December 31, 2024, is outlined in the table below.
FundSteelworkers Pension Trust
EIN / PN23-6648508 / 499
Pension Protection Act Zone Status 2023 (1)
 Green
Pension Protection Act Zone Status 2022 (1)
 Green
Subject to Financial Improvement/Rehabilitation Plan (2)
 No
Contributions of Century Aluminum 2024$0.04
Contributions of Century Aluminum 2023$0.2
Contributions of Century Aluminum 2022$1.6
Withdrawal from Plan ProbableNo
Surcharge Imposed No
Expiration Date of Collective Bargaining Agreement (2)
March 31, 2026
(1)The most recent Pension Protection Act zone status available in 2024 and 2023 is for the plan's year-end December 31, 2023 and December 31, 2022, respectively. The zone status is based on information that Century received from the plan as well as publicly available information per the Department of Labor and is certified by the plan’s actuary. Among other factors, plans in the green zone are at least 80 percent funded.
(2)The “Subject to Financial Improvement / Rehabilitation Plan” column indicates plans for which a financial improvement plan (FIP) or a rehabilitation plan (RP) is either pending or has been implemented. The last column lists the expiration date(s) of the collective-bargaining agreement(s) to which the plans are subject.
v3.25.0.1
Share-based Compensation (Tables)
 12 Months Ended
Dec. 31, 2024
Share-Based Payment Arrangement [Abstract]  
Summary of service-based share awards activity
Service-based share awardsNumber
Outstanding at January 1, 2024
1,156,774 
Granted650,755 
Vested(263,227)
Forfeited(139,407)
Outstanding at December 31, 2024
1,404,895 
Performance-based share awardsNumber
Outstanding at January 1, 2024
602,564 
Granted475,226 
Vested(303,315)
Forfeited— 
Outstanding at December 31, 2024
774,475 
 Year ended December 31,
Service-based share awards202420232022
Weighted average per share fair value of service-based share grants$10.11 $12.58 $17.30 
Summary of share-based compensation expense
The following table summarizes the compensation cost recognized for the years ended December 31, 2024, 2023 and 2022 for all service-based and performance-based share awards. The compensation cost is included as part of selling, general and administrative expenses and cost of goods sold in our Consolidated Statements of Operations.
Year ended December 31,
202420232022
Share-based compensation (benefit) expense reported:   
Performance-based share (benefit) expense$9.3 $2.0 $(5.0)
Service-based share expense6.1 4.6 4.4 
Total share-based compensation (benefit) expense before income tax15.4 6.6 (0.6)
Income tax— — — 
Total share-based compensation (benefit) expense, net of income tax$15.4 $6.6 $(0.6)
v3.25.0.1
Earnings Per Share (Tables)
 12 Months Ended
Dec. 31, 2024
Earnings Per Share [Abstract]  
Schedule of basic and diluted earnings (loss) per share and securities excluded from the calculation of diluted EPS
The following table shows the basic and diluted earnings (loss) per share for 2024, 2023, and 2022:
For the year ended December 31, 2024
Net Income
Shares
(in millions)
Per Share
Net income attributable to Century stockholders
$336.8 
Less: net income allocated to participating securities17.9 
Basic EPS:   
Net income allocated to common stockholders$318.9 92.8 $3.44 
Effect of Dilutive Securities(1):
Share-based compensation— 1.0 
 Convertible senior notes 2.7 4.6 
Diluted EPS:
Net income allocated to common stockholders
$321.6 98.4 $3.27 
For the year ended December 31, 2023
Net Loss
Shares
(in millions)
Per Share
Net loss attributable to Century stockholders$(43.1)
Amount allocated to common stockholders100 %
Basic and Diluted EPS:(1)
$(43.1)92.4 $(0.47)
For the year ended December 31, 2022
Net Loss
Shares
(in millions)
Per Share
Net loss attributable to Century stockholders$(14.1)  
Amount allocated to common stockholders100 %  
Basic and Diluted EPS:(1)
$(14.1)91.4 $(0.15)
Securities excluded from the calculation of diluted EPS (in millions)(1):
2024
2023
2022
Share-based compensation
0.6 1.0 1.7 
Convertible preferred shares5.2 5.4 5.8 
Convertible senior notes— 4.6 4.6 
(1)In periods when we report a net loss, all share-based compensation awards, convertible preferred shares and convertible senior notes are excluded from the calculation of diluted weighted average shares outstanding because of their anti-dilutive effect on earnings (loss) per share.
v3.25.0.1
Income Taxes (Tables)
 12 Months Ended
Dec. 31, 2024
Income Tax Disclosure [Abstract]  
Components of pre-tax book income (loss)
The components of pre-tax book income (loss) consist of the following:
Year Ended December 31,
202420232022
U.S.$335.5 $78.0 $(193.6)
Foreign (11.7)(144.8)227.0 
Total $323.8 $(66.8)$33.4 
Significant components of the income before income tax expense
Significant components of income tax expense consist of the following:
Year Ended December 31,
202420232022
Current:   
U.S. federal current expense (benefit)$— $0.5 $— 
State current expense (benefit)— — 0.2 
Foreign current expense (benefit)4.9 15.8 4.0 
Total current expense (benefit)4.9 16.3 4.2
Deferred:   
U.S. federal deferred benefit— (0.3)(0.3)
State deferred benefit— (0.1)— 
Foreign deferred tax (benefit) expense(1.7)(30.5)43.5 
Total deferred (benefit) expense(1.7)(30.9)43.2 
Total income tax (benefit) expense$3.2 $(14.6)$47.4 
Reconciliation of the statutory U.S. Federal income tax rate to the effective income tax rate on income (loss)
A reconciliation of the statutory U.S. Federal income tax rate to the effective income tax rate on income (loss) is as follows:
Year Ended December 31,
 202420232022
Federal Statutory Rate21.0 %21.0 %21.0 %
Permanent differences1.0 1.1 (15.2)
State taxes, net of Federal benefit— (0.1)0.1 
Rate change(0.5)(0.3)0.4 
Foreign earnings taxed at different rates than U.S.— 2.0 (0.8)
Valuation allowance(11.3)3.6 (4.2)
Foreign dividends and inclusions0.5 (12.7)122.9 
Net operating loss expiration and remeasurement2.8 (8.0)43.1 
Filing differences8.7 0.6 (19.1)
Changes in uncertain tax reserves0.2 (1.3)(5.3)
Advanced Manufacturing Production Credit(5.9)18.6 — 
Bargain Purchase gain
(15.7)— — 
Other0.2 (2.7)(0.9)
Effective tax rate1.0 %21.8 %142.0 %
Significant components of deferred tax assets and liabilities
The significant components of our deferred tax assets and liabilities as of December 31 are as follows:
20242023
Deferred tax assets:  
Accrued postretirement benefit cost$30.1 $30.7 
Net operating losses 473.3 467.6 
Disallowed interest expense37.1 29.2 
Derivative and hedging contracts0.1 1.2 
Fixed asset tax over book basis— 9.2 
Other29.4 28.3 
Total deferred tax assets570.0 566.2 
Valuation allowance(504.4)(537.6)
Net deferred tax assets$65.6 $28.6 
Deferred tax liabilities:  
Fixed asset book over tax basis(115.9)(62.0)
Derivatives— — 
Foreign basis differences0.6 (18.1)
Other(21.4)(20.6)
Total deferred tax liabilities(136.7)(100.7)
Net deferred tax liability$(71.1)$(72.1)
Changes in valuation allowance
The changes in the valuation allowance are as follows:
Year Ended December 31,
202420232022
Beginning balance, valuation allowance$537.6 $487.9 $485.8 
Remeasurement of deferred tax assets— — — 
Release of valuation allowance— — — 
Expiration of net operating losses(6.1)(7.2)(15.4)
Other change in valuation allowance(27.1)56.9 17.5 
Ending balance, valuation allowance$504.4 $537.6 $487.9 
Significant components of net operating loss carryforwards
The significant components of our NOLs are as follows:
20242023
Federal (1)
$1,571.2 $1,533.5 
State (2)
1,163.5 1,221.0 
Foreign (3)(4)
342.2 344.4 
(1)US federal NOLs begin to expire in 2028.
(2)US state NOLs begin to expire in 2027.
(3)NOLs in Iceland expire between 2025 and 2026.
(4)NOLs in Jamaica do not expire.
Reconciliation of beginning and ending amounts of gross unrecognized tax benefits
A reconciliation of the beginning and ending amounts of gross unrecognized tax benefits (excluding interest) is as follows:
202420232022
Balance as of January 1,  $3.0 $2.2 $4.0 
Additions based on tax positions related to the current year0.6 1.3 0.3 
Decreases due to lapse of applicable statute of limitations(0.1)(0.5)(2.1)
Balance as of December 31,$3.5 $3.0 $2.2 
v3.25.0.1
Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2024
Asset Retirement Obligation Disclosure [Abstract]  
Schedule of changes in asset retirement obligations
The reconciliation of the changes in our AROs is presented below:
Year ended December 31,
20242023
Beginning balance$51.1 $21.2 
Additional ARO liabilities incurred6.7 3.1 
ARO liabilities settled(4.6)(1.5)
Accretion expense2.1 2.0 
Acquired ARO liabilities (See Note 2)— 23.9 
Revisions in estimated cash flows10.8 2.4 
Ending balance$66.1 $51.1 
Current portion of asset retirement obligations (1)
4.6 1.6 
Asset retirement obligations - less current portion$61.5 $49.5 
v3.25.0.1
Business Segments (Tables)
 12 Months Ended
Dec. 31, 2024
Segment Reporting [Abstract]  
Reconciliation of assets from segment to consolidated
A reconciliation of our consolidated assets to the total of primary aluminum segment assets and capital expenditures is provided below.
Segment assets (1)
202420232022
Aluminum$1,896.6 $1,808.1 $1,432.4 
Corporate, unallocated42.8 38.4 39.6 
Total assets$1,939.4 $1,846.5 $1,472.0 
Capital expenditures$82.3 $95.0 $86.3 
(1)Segment assets include accounts receivable, due from affiliates, prepaid and other current assets, leases - right of use assets, inventory, intangible assets and property, plant and equipment, net; the remaining assets are unallocated corporate assets.
Schedule of revenue from external customers and long-lived assets, by geographical areas Included in the consolidated financial statements are the following amounts related to geographic locations:
 202420232022
Net sales: (1)
   
United States$1,427.0 $1,358.6 $1,737.2 
Iceland793.3 826.8 1,040.1 
Total Net sales
2,220.3 2,185.4 2,777.3 
Long-lived assets: (2)
   
United States$233.6 $219.1 $244.9 
Iceland526.4 529.4 491.0 
Jamaica255.2 275.8 — 
Other50.6 55.1 58.3 
(1)Includes sales of primary aluminum, scrap aluminum and alumina, and purchased aluminum and alumina.
(2)Includes long-lived assets other than financial instruments and deferred taxes.
Schedule of revenue by major customers by reporting segments A loss of these customers could have a material adverse effect on our results of operations. The net sales related to the customers is as follows:
Year Ended December 31,
202420232022
Glencore$1,312.1 $1,612.1 $1,671.1 
Southwire— — 331.3 
Schedule of segment information
The following table presents our segment information to reconcile to Segment EBITDA for the periods indicated and, because we only have one segment, our net income (loss) attributable to Century stockholders is identical to the information presented in the Consolidated Statements of Operations:
Year Ended December 31,
202420232022
Net sales$2,220.3 $2,185.4 $2,777.3 
Segment Cost of goods sold(1)
(2,014.7)(2,056.9)(2,597.0)
IRA Credit - Cost of goods sold(2)
89.7 56.5 — 
Asset impairment
— — (159.4)
Other segment items(3)
(25.4)(55.7)(12.9)
Segment EBITDA
269.9 129.3 8.0 
Depreciation, depletion, and amortization - Cost of goods sold(86.5)(80.7)(76.4)
Selling, general and administrative expenses(56.8)(44.3)(37.5)
Interest expense - affiliates(6.7)(1.8)— 
Interest expense(36.4)(33.7)(29.3)
Interest income2.1 2.0 0.5 
Net gain (loss) on forward and derivative contracts - nonaffiliates2.5 (62.4)210.4 
Net gain (loss) on forward and derivative contracts - affiliates(0.5)0.6 (13.3)
Bargain purchase gain245.9 — — 
Other(4)
(9.7)24.1 (29.1)
Income tax benefit (expense)(3.2)14.6 (47.4)
Net income (loss)320.6 (52.3)(14.1)
Net loss attributable to noncontrolling interests
16.2 9.2 — 
Net income (loss) attributable to Century stockholders, as reported$336.8 $(43.1)$(14.1)
(1)Includes raw materials, labor, energy, and other direct cost of goods sold.
(2)Advanced production credit related to Section 45X of the Inflation Reduction Act.
(3)Includes freight costs and FIFO inventory adjustment.
(4)Includes equity in losses or earnings from joint ventures and inventory revaluation to lower of cost or net realizable value.
v3.25.0.1
Derivatives (Tables)
 12 Months Ended
Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Schedule of derivatives not designated as hedging instruments
The following table sets forth the Company's derivative assets and liabilities that were accounted for at fair value and not designated as cash flow hedges as of December 31, 2024 and 2023, respectively:
Asset Fair Value
20242023
Commodity contracts (1)
$4.5 $2.9 
Foreign exchange contracts (2)
— — 
Total$4.5 $2.9 
 Liability Fair Value
20242023
Commodity contracts (1)
4.4 7.8 
Foreign exchange contracts (2)
— 0.1 
Total$4.4 $7.9 
(1)Commodity contracts reflect our outstanding LME and MWP forward financial sales contracts, fixed for floating swaps, HFO price swaps and Indiana Hub power price swaps. At December 31, 2024, $0.0 million of Due to affiliates was related to commodity contract liabilities with Glencore. At December 31, 2023, $6.4 million of Due to affiliates was related to commodity contract liabilities with Glencore.
(2)Foreign exchange contracts reflect our outstanding FX swaps and casthouse currency hedges.
Schedule of derivative instruments
The following table summarizes the net gain (loss) on forward and derivative contracts for the years ended December 31, 2024, 2023, and 2022:
Year Ended December 31,
202420232022
Commodity contracts (1)
$2.1 $63.5 $206.6 
Foreign exchange contracts(0.1)(1.7)(9.4)
   Total$2.0 $61.8 $197.2 
(1)For the years ended December 31, 2024, 2023, and 2022, $(0.5) million, $0.6 million, and $(13.3) million of net gain (loss), respectively, was with Glencore.
v3.25.0.1
Variable Interest Entity (Tables)
 12 Months Ended
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Schedule of Consolidated VIE's Assets and Liabilities
The table below shows the carrying amounts and classification of the consolidated VIE's assets and liabilities included in the Consolidated Balance Sheets as of December 31, 2024 and 2023.
December 31,
20242023
ASSETS
Cash and cash equivalents17.4 7.4 
Accounts receivable - net1.1 — 
Non-trade receivables13.1 38.3 
Due from affiliates75.1 76.7 
Inventories109.8 96.6 
Prepaid and other current assets2.0 8.7 
Total current assets218.5 227.7 
Property, plant and equipment - net232.1 248.7 
Other assets23.1 27.1 
TOTAL473.7 503.5 
LIABILITIES
LIABILITIES:
Accounts payable, trade39.1 73.1 
Accrued compensation and benefits8.5 2.3 
Due to affiliates49.6 55.4 
Accrued and other current liabilities7.2 7.1 
Total current liabilities104.4 137.9 
Accrued benefits costs - less current portion17.7 0.8 
Other liabilities66.7 36.1 
Asset retirement obligations - less current portion35.0 26.0 
Total noncurrent liabilities119.4 62.9 
TOTAL
223.8 200.8 
v3.25.0.1
Summary of Significant Accounting Policies (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Property, Plant and Equipment [Line Items]    
Allowance for expected losses $ 0.5 $ 0.5
Minimum | Building and Improvements    
Property, Plant and Equipment [Line Items]    
Useful life 10 years  
Minimum | Machinery and Equipment    
Property, Plant and Equipment [Line Items]    
Useful life 5 years  
Minimum | Technology and Software    
Property, Plant and Equipment [Line Items]    
Useful life 3 years  
Maximum | Building and Improvements    
Property, Plant and Equipment [Line Items]    
Useful life 45 years  
Maximum | Machinery and Equipment    
Property, Plant and Equipment [Line Items]    
Useful life 35 years  
Maximum | Technology and Software    
Property, Plant and Equipment [Line Items]    
Useful life 7 years  
Jamalco    
Schedule of Equity Method Investments [Line Items]    
Ownership percentage 55.00%  
Century Aluminum    
Schedule of Equity Method Investments [Line Items]    
Glencore beneficial ownership 42.90%  
Glencore economic ownership 45.80%  
v3.25.0.1
Acquisition of Jamalco - Narrative (Details) - USD ($)
 3 Months Ended 12 Months Ended
May 02, 2023
Mar. 31, 2024
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Business Acquisition [Line Items]          
Bargain purchase gain     $ 245,900,000 $ 0 $ 0
General Alumina Holdings Limited          
Business Acquisition [Line Items]          
Payments to acquire business $ 1.00        
Bargain purchase gain     $ 245,900,000 273,400,000  
Property, plant and equipment reduction   $ 29,000,000      
Purchase, gain reduction   $ 29,000,000      
Jamalco          
Business Acquisition [Line Items]          
Revenue since acquisition       150,300,000  
Loss of acquiree since acquisition       41,100,000  
Transaction costs       $ 1,400,000  
Jamalco          
Business Acquisition [Line Items]          
Ownership percentage     55.00%    
Jamalco | General Alumina Holdings Limited          
Business Acquisition [Line Items]          
Ownership percentage 55.00%        
Jamalco | Clarendon Alumina Production Limited          
Business Acquisition [Line Items]          
Glencore beneficial ownership 45.00%        
v3.25.0.1
Acquisition of Jamalco - Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
May 02, 2023
Business Acquisition [Line Items]      
Bargain purchase gain $ 0.0 $ 273.4  
General Alumina Holdings Limited      
Business Acquisition [Line Items]      
Cash and cash equivalents     $ 19.4
Restricted cash     8.3
Accounts receivable - net     7.7
Non-trade receivables     40.4
Inventories     103.9
Prepaid and other current assets     4.2
Property, plant and equipment     217.2
Other assets     26.1
Accounts payable, trade     (94.6)
Accrued and other current liabilities     (29.5)
Other liabilities     (36.5)
Asset retirement obligations     (23.9)
Total identifiable assets acquired and liabilities assumed     242.7
Less: noncontrolling interest     (3.2)
Bargain purchase gain     $ 245.9
v3.25.0.1
Acquisition of Jamalco - Unaudited Pro Forma Financial Information (Details) - General Alumina Holdings Limited - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Business Acquisition [Line Items]    
Revenue $ 2,235.1 $ 2,831.0
Earnings $ (45.9) $ (33.1)
v3.25.0.1
Curtailment of Operations - Hawesville (Details) - Curtailment Of Operations - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]    
Severance costs $ 6.8 $ 16.6
Gain (loss) on material sales $ 0.5 1.7
Temporary Facility Closing, Excess Capacity    
Restructuring Cost and Reserve [Line Items]    
Excess capacity charges   $ 9.0
Restructuring Incurred Cost, Statement Of Income Or Comprehensive Income, Extensible Enumeration, Not Disclosed Flag   demand capacity charges
v3.25.0.1
Related Party Transactions - Narrative (Details)
€ in Millions, $ in Millions
 1 Months Ended 12 Months Ended
Oct. 01, 2024
USD ($)
Aug. 30, 2024
EUR (€)
carbon_credit
Dec. 18, 2023
EUR (€)
carbon_credit
€ / carbonCredit
Sep. 28, 2023
EUR (€)
carbon_credit
€ / carbonCredit
Dec. 31, 2024
EUR (€)
carbon_credit
€ / carbonCredit
Aug. 31, 2024
EUR (€)
carbon_credit
€ / carbonCredit
Mar. 31, 2024
EUR (€)
€ / carbonCredit
Dec. 31, 2024
USD ($)
carbon_credit
€ / carbonCredit
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Related Party Transaction [Line Items]                    
Total net sales | $               $ 2,220.3 $ 2,185.4 $ 2,777.3
Vlissingen Facility Agreement | Affiliated Entity | Vlissingen                    
Related Party Transaction [Line Items]                    
Term extension 2 years                  
Credit facility face amount | $ $ 90.0                  
Stated interest rate, percentage 8.75%                  
Debt instrument, basis spread on variable rate 3.687%                  
Vlissingen Facility Agreement | Affiliated Entity | Vlissingen | Maximum                    
Related Party Transaction [Line Items]                    
Variable interest rate 9.00%                  
Vlissingen Facility Agreement | Affiliated Entity | Vlissingen | Minimum                    
Related Party Transaction [Line Items]                    
Variable interest rate 7.00%                  
Carbon Credit Sale | Affiliated Entity | Nordural Grundartangi ehf                    
Related Party Transaction [Line Items]                    
Carbon credit sold in transaction | carbon_credit     40,000 390,000 370,700 370,700   370,700    
Sale price (Euro per carbon credit) | € / carbonCredit     69.30 82.18            
Aggregate amount       € 32.1            
Carbon Credit Repurchase | Affiliated Entity | Nordural Grundartangi ehf                    
Related Party Transaction [Line Items]                    
Sale price (Euro per carbon credit) | € / carbonCredit     85.13 83.72 69.16 71.20 87.01 69.16    
Aggregate amount     € 33.2 € 32.7 € 25.6 € 26.4 € 33.9      
Additional Carbon Credit Repurchase | Affiliated Entity | Nordural Grundartangi ehf                    
Related Party Transaction [Line Items]                    
Sale price (Euro per carbon credit) | € / carbonCredit     70.71              
Aggregate amount     € 2.8              
Second Repurchase Agreement, Carbon Credit Repurchase | Affiliated Entity | Nordural Grundartangi ehf                    
Related Party Transaction [Line Items]                    
Sale price (Euro per carbon credit) | € / carbonCredit             72.59      
Aggregate amount             € 2.9      
Repurchase Agreement, Carbon Credits Settled | Affiliated Entity | Nordural Grundartangi ehf                    
Related Party Transaction [Line Items]                    
Carbon credit sold in transaction | carbon_credit   59,300                
Aggregate amount   € 11.1                
Glencore | Supply Commitment                    
Related Party Transaction [Line Items]                    
Total net sales | $               $ 191.3 $ 191.7 $ 24.9
Glencore | Sales Revenue | Customer Concentration Risk                    
Related Party Transaction [Line Items]                    
Concentration risk, percentage               59.10% 73.80% 60.20%
Century Aluminum                    
Related Party Transaction [Line Items]                    
Glencore beneficial ownership         42.90%     42.90%    
Glencore economic ownership         45.80%     45.80%    
v3.25.0.1
Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Related Party Transaction [Line Items]      
Net sales $ 2,220.3 $ 2,185.4 $ 2,777.3
Related Party      
Related Party Transaction [Line Items]      
Net sales 1,312.1 1,612.1 1,671.1
Related Party | Glencore      
Related Party Transaction [Line Items]      
Net sales 1,312.1 1,612.1 1,671.1
Purchases from Glencore $ 277.9 $ 181.4 $ 284.7
v3.25.0.1
Revenue - Breakdown of Revenue (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Disaggregation of Revenue [Line Items]      
Net sales $ 2,220.3 $ 2,185.4 $ 2,777.3
Contract liabilities 41.2 30.6  
Aluminum      
Disaggregation of Revenue [Line Items]      
Net sales 1,882.1 1,972.6 2,750.3
Alumina      
Disaggregation of Revenue [Line Items]      
Net sales 338.2 212.8 27.0
United States      
Disaggregation of Revenue [Line Items]      
Net sales 1,427.0 1,358.6 1,737.2
Iceland      
Disaggregation of Revenue [Line Items]      
Net sales $ 793.3 $ 826.8 $ 1,040.1
v3.25.0.1
Leases (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Lessee, Lease, Description [Line Items]    
Operating lease, weighted average remaining lease term 10 years 1 month 6 days 11 years 9 months 18 days
Operating lease, weighted average discount rate, percent 7.50% 7.30%
Right-of-use asset obtained in exchange for operating lease liability $ 2.0 $ 3.2
Operating lease, payments $ 5.0 4.6
Jamalco    
Lessee, Lease, Description [Line Items]    
Additional right of use assets from acquisition   $ 2.4
v3.25.0.1
Leases - ROU (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Leases [Abstract]    
ROUA [extensible list] Other assets Other assets
ROUA $ 21.0 $ 24.7
ROUL - current [extensible list] Accrued and other current liabilities Accrued and other current liabilities
ROUL - current $ 3.0 $ 2.3
ROUL -, noncurrent [extensible list] Other Liabilities, Noncurrent Other Liabilities, Noncurrent
ROUL - non-current $ 18.7 $ 21.9
ROUL $ 21.7 $ 24.2
v3.25.0.1
Leases - Maturities (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Leases [Abstract]    
2025 $ 3.9  
2026 3.3  
2027 2.8  
2028 2.8  
2029 2.7  
Thereafter 16.2  
Total 31.7  
Less: Interest (10.0)  
ROUL $ 21.7 $ 24.2
v3.25.0.1
Leases - Operating Expense (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Leases [Abstract]    
Operating leases expense $ 5.3 $ 4.9
Short term lease expense 3.2 0.6
Total $ 8.5 $ 5.5
v3.25.0.1
Fair Value Measurements - Recurring Fair Value Measurements (Details) - USD ($)
Dec. 31, 2024
Dec. 31, 2023
ASSETS:    
TOTAL $ 12,700,000 $ 19,900,000
LIABILITIES:    
TOTAL 4,400,000 7,900,000
Fair Value, Recurring    
ASSETS:    
Cash equivalents 7,900,000 16,800,000
Trust assets 300,000 200,000
Derivative instruments 4,500,000 2,900,000
LIABILITIES:    
Derivative instruments 4,400,000 7,900,000
Level 1    
ASSETS:    
TOTAL 8,200,000 17,000,000.0
LIABILITIES:    
TOTAL 0 0
Level 1 | Fair Value, Recurring    
ASSETS:    
Cash equivalents 7,900,000 16,800,000
Trust assets 300,000 200,000
Derivative instruments 0 0
LIABILITIES:    
Derivative instruments 0 0
Level 2    
ASSETS:    
TOTAL 4,500,000 2,900,000
LIABILITIES:    
TOTAL 4,400,000 7,900,000
Level 2 | Fair Value, Recurring    
ASSETS:    
Cash equivalents 0 0
Trust assets 0 0
Derivative instruments 4,500,000 2,900,000
LIABILITIES:    
Derivative instruments 4,400,000 7,900,000
Level 3    
ASSETS:    
TOTAL 0 0
LIABILITIES:    
TOTAL 0 0
Level 3 | Fair Value, Recurring    
ASSETS:    
Cash equivalents 0 0
Trust assets 0 0
Derivative instruments 0 0
LIABILITIES:    
Derivative instruments $ 0 $ 0
v3.25.0.1
Fair Value Measurements - Narrative (Details) - USD ($)
Dec. 31, 2024
Dec. 31, 2023
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Assets, fair value $ 12,700,000 $ 19,900,000
Liabilities, fair value 4,400,000 7,900,000
Level 3    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Assets, fair value 0 0
Liabilities, fair value $ 0 $ 0
v3.25.0.1
Fair Value Measurements - Level 3 Reconciliation (Details) - LME forward financial sales contracts - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Beginning balance $ 0.0 $ 1.8
Transfers out of Level 3   (1.8)
Transactions during 2024 0.0  
Ending balance 0.0 0.0
Change in unrealized gains (losses) 0.0 0.0
Beginning balance 0.0 (4.6)
Transfers out of Level 3   4.6
Transactions during 2024 0.0  
Ending balance 0.0 0.0
Change in unrealized gains (losses) $ 0.0 $ 0.0
v3.25.0.1
Debt - Activity (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Oct. 01, 2024
Dec. 31, 2023
Apr. 14, 2021
Apr. 09, 2021
Debt Instrument [Line Items]          
Total $ 528.2   $ 479.2    
Industrial Revenue Bonds, Variable          
Debt Instrument [Line Items]          
Maximum variable interest rate 12.00%        
Hancock County industrial revenue bonds ("IRBs") due April 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) $ 7.8   7.8    
Revolving Credit Facility | U.S revolving credit facility          
Debt Instrument [Line Items]          
Revolving credit facility $ 20.0   23.7    
Stated interest rate, percentage 8.00%        
Revolving Credit Facility | Foreign line of credit          
Debt Instrument [Line Items]          
Revolving credit facility $ 34.0   0.0    
Stated interest rate, percentage 7.84%        
Casthouse Facility | Foreign line of credit          
Debt Instrument [Line Items]          
Revolving credit facility $ 9.0   5.5    
Financing fees 0.0        
Secured debt $ 114.2   98.8    
Stated interest rate, percentage 8.06%        
Iceland Term Facility | Foreign line of credit          
Debt Instrument [Line Items]          
Revolving credit facility $ 0.0   1.3    
Stated interest rate, percentage 3.20%        
Vlissingen Facility Agreement | Foreign line of credit          
Debt Instrument [Line Items]          
Revolving credit facility $ 0.0   10.0    
Secured debt $ 10.0   0.0    
Stated interest rate, percentage 7.99% 8.75%      
Senior Secured Notes, 7.5% | Senior Notes          
Debt Instrument [Line Items]          
Financing fees $ 1.9        
Stated interest rate, percentage 7.50%     7.50%  
7.5% senior secured notes due April 1, 2028, net of financing fees of $1.9 million at December 31, 2024, interest payable semiannually $ 248.1   247.4    
Senior Convertible Notes, 2.75% | Senior Notes          
Debt Instrument [Line Items]          
Financing fees $ 1.2        
Stated interest rate, percentage 2.75%       2.75%
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.2 million at December 31, 2024, interest payable semiannually $ 85.1   $ 84.7    
Industrial revenue bonds due 2028          
Debt Instrument [Line Items]          
Stated interest rate, percentage 3.75%        
v3.25.0.1
Debt - Narrative (Details)
$ / shares in Units, € in Millions
 12 Months Ended
Oct. 01, 2024
USD ($)
Nov. 02, 2021
USD ($)
Apr. 14, 2021
USD ($)
Apr. 09, 2021
USD ($)
$ / shares
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Sep. 30, 2022
EUR (€)
Sep. 28, 2022
USD ($)
Jun. 14, 2022
USD ($)
Feb. 04, 2022
USD ($)
Nov. 30, 2013
USD ($)
Senior Secured Notes, 7.5% | Senior Notes                      
Debt Instrument [Line Items]                      
Stated interest rate, percentage     7.50%   7.50%            
Face amount     $ 250,000,000                
Proceeds from issuance of Senior Notes due 2028     $ 245,200,000                
Redemption price, percentage         100.00%            
Redemption period         12 months            
Percentage of outstanding amount, offer to purchase         101.00%            
Senior Secured Notes, 7.5% | Senior Notes | Level 2                      
Debt Instrument [Line Items]                      
Fair value of debt instrument         $ 253,100,000            
Senior Convertible Notes, 2.75% | Senior Notes                      
Debt Instrument [Line Items]                      
Stated interest rate, percentage       2.75% 2.75%            
Face amount       $ 86,300,000              
Percentage of principal amount redeemed       100.00% 100.00%            
Proceeds from issuance of Convertible Senior Notes       $ 83,700,000              
Conversion ratio       0.0533547              
Conversion price (in dollars per share) | $ / shares       $ 18.74              
Debt instrument, convertible, threshold percentage of stock price trigger         130.00%            
Debt instrument, trading days, term         20 days            
Debt instrument, consecutive trading days, term         30 days            
Senior Convertible Notes, 2.75% | Senior Notes | Level 2                      
Debt Instrument [Line Items]                      
Fair value of debt instrument         $ 102,600,000            
Revolving Credit Facility | U.S revolving credit facility                      
Debt Instrument [Line Items]                      
Stated interest rate, percentage         8.00%            
Credit facility face amount                 $ 250,000,000.0    
Letter of credit sub-facility amount         $ 65,600,000            
Outstanding borrowings         20,000,000.0            
Outstanding letters of credit issued         63,700,000            
Credit facility maximum amount         $ 250,000,000.0            
Revolving Credit Facility | Letter of Credit                      
Debt Instrument [Line Items]                      
Letter of credit sub-facility amount                 $ 150,000,000.0    
Revolving Credit Facility | Foreign line of credit                      
Debt Instrument [Line Items]                      
Stated interest rate, percentage         7.84%            
Credit facility face amount               $ 100,000,000.0     $ 50,000,000
Outstanding borrowings         $ 34,000,000.0            
Outstanding letters of credit issued         0            
Credit facility maximum amount         100,000,000.0         $ 80,000,000.0  
Casthouse Facility                      
Debt Instrument [Line Items]                      
Credit facility face amount   $ 130,000,000.0                  
Debt instrument, term   8 years                  
Debt instrument, quarterly installment fee   1.739%                  
Debt instrument, remaining payment after drawdown of funds   60.00%                  
Medium-term notes, outstanding borrowings         $ 123,200,000            
Debt instrument, arrangement fee, percentage of facility   0.78%                  
Debt instrument, arrangement fee, paid upfront   50.00%                  
Debt instrument, arrangement fee, paid at end of availability   50.00%                  
Line of credit facility, unused capacity, commitment fee percentage   0.38%                  
Casthouse Facility | Foreign line of credit                      
Debt Instrument [Line Items]                      
Stated interest rate, percentage         8.06%            
Secured debt         $ 114,200,000 $ 98,800,000          
Casthouse Facility | Secured Debt                      
Debt Instrument [Line Items]                      
Long-term debt   $ 430,000,000                  
Medium-term Notes                      
Debt Instrument [Line Items]                      
Credit facility face amount | €             € 13.6        
Iceland Term Facility | Foreign line of credit                      
Debt Instrument [Line Items]                      
Stated interest rate, percentage         3.20%            
Vlissingen Credit Facility | Foreign line of credit                      
Debt Instrument [Line Items]                      
Stated interest rate, percentage 8.75%       7.99%            
Credit facility face amount $ 90,000,000                    
Term extension 2 years                    
Secured debt         $ 10,000,000.0 $ 0          
Debt instrument, basis spread on variable rate 3.687%                    
Vlissingen Credit Facility | Foreign line of credit | Maximum                      
Debt Instrument [Line Items]                      
Variable interest rate 9.00%                    
Vlissingen Credit Facility | Foreign line of credit | Minimum                      
Debt Instrument [Line Items]                      
Variable interest rate 7.00%                    
Industrial Revenue Bonds, Variable                      
Debt Instrument [Line Items]                      
Maximum variable interest rate         12.00%            
Surety Bond                      
Debt Instrument [Line Items]                      
Loss contingency accrual         $ 6,600,000            
v3.25.0.1
Debt - Redemption Rights (Details) - Senior secured notes due June 01, 2025 - Long-term Debt
 12 Months Ended
Dec. 31, 2024
2024  
Debt Instrument [Line Items]  
Redemption price, percentage 103.75%
2025  
Debt Instrument [Line Items]  
Redemption price, percentage 101.875%
2026 and Thereafter  
Debt Instrument [Line Items]  
Redemption price, percentage 100.00%
v3.25.0.1
Debt - U.S. Credit Facility Schedule (Details) - U.S revolving credit facility - Revolving Credit Facility
$ in Millions
Dec. 31, 2024
USD ($)
Line of Credit Facility [Line Items]  
Credit facility maximum amount $ 250.0
Borrowing availability 149.3
Outstanding letters of credit issued 63.7
Outstanding borrowings 20.0
Borrowing availability, net of outstanding letters of credit and borrowings $ 65.6
v3.25.0.1
Debt - Iceland Credit Facility Schedule (Details) - Foreign line of credit - Revolving Credit Facility - USD ($)
$ in Millions
Dec. 31, 2024
Feb. 04, 2022
Line of Credit Facility [Line Items]    
Credit facility maximum amount $ 100.0 $ 80.0
Borrowing availability 100.0  
Outstanding letters of credit issued 0.0  
Outstanding borrowings 34.0  
Borrowing availability, net of outstanding letters of credit and borrowings $ 66.0  
v3.25.0.1
Shareholders' Equity (Details) - USD ($)
 117 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Mar. 31, 2015
Dec. 31, 2011
Dec. 31, 2008
Class of Stock [Line Items]          
Common stock, shares authorized (shares) 195,000,000 195,000,000      
Common stock, par value (in dollars per share) $ 0.01 $ 0.01      
Common stock, shares issued (shares) 100,475,086 99,876,385      
Common stock, shares outstanding (shares) 93,288,565 92,689,864      
Preferred stock, shares authorized (shares) 5,000,000 5,000,000      
Preferred stock, par value (in dollars per share) $ 0.01 $ 0.01      
Conversion of convertible preferred stock (shares) 100        
Liquidation preference (in dollars per share) $ 0.01        
Authorized repurchase amount $ 130,000,000.0     $ 60,000,000.0  
Additional repurchase amount     $ 70,000,000.0    
Treasury stock, common (in shares) 7,186,521        
Treasury stock, value $ 86,300,000 $ 86,300,000      
Repurchase of common stock (shares) 0        
Remaining authorized repurchase amount $ 43,700,000        
Series A Convertible Preferred Stock          
Class of Stock [Line Items]          
Preferred stock, par value (in dollars per share) $ 0.01        
Preferred stock, shares issued (shares)         160,000
Shares, outstanding (in shares) 49,715 52,284      
v3.25.0.1
Inventories (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Inventory, Net [Abstract]    
Raw materials $ 180.8 $ 162.5
Work-in-process 52.1 42.9
Finished goods 74.6 46.3
Operating and other supplies 231.5 225.3
Inventories $ 539.0 $ 477.0
v3.25.0.1
Property, Plant and Equipment (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Property, Plant and Equipment [Abstract]    
Land and improvements $ 104.3 $ 105.1
Mineral Reserves 34.7 35.8
Buildings and improvements 404.3 328.8
Machinery and equipment 1,664.0 1,580.7
Asset Retirement Obligation 35.3 21.8
Construction in progress 44.7 160.3
Property, plant and equipment, gross 2,287.3 2,232.5
Less accumulated depreciation, amortization and depletion (1,309.0) (1,228.3)
Property, plant and equipment - net $ 978.3 $ 1,004.2
v3.25.0.1
Property, Plant and Equipment (Detail Textual) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Property, Plant and Equipment [Abstract]      
Depreciation, depletion and amortization $ 81.8 $ 74.7 $ 73.4
v3.25.0.1
Accumulated Other Comprehensive Loss ("AOCL") - Components of Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Other comprehensive loss before income tax effect $ (105.6) $ (100.2)
Income tax effect 2.3 2.3
Accumulated other comprehensive loss (103.3) (97.9)
Defined benefit plan and other postretirement liabilities    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Other comprehensive loss before income tax effect (107.0) (101.8)
Income tax effect 2.6 2.6
Unrealized gain (loss) on financial instruments    
Accumulated Other Comprehensive Income (Loss) [Line Items]    
Other comprehensive loss before income tax effect 1.4 1.6
Income tax effect $ (0.3) $ (0.3)
v3.25.0.1
Accumulated Other Comprehensive Loss ("AOCL") - Changes In Components Of Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Beginning balance $ 355.6    
Other comprehensive income (loss) before reclassifications (11.9) $ (10.1) $ (5.9)
Net amount reclassified to net income (loss) 6.5 6.2 (5.8)
Ending balance 694.4 355.6  
Costs of goods sold [1] 2,035.3 2,093.5 2,730.6
Other income, net (4.5) (3.3) 15.3
Selling, general and administrative expenses 56.8 44.3 37.5
Other operating expense (income), net 6.8 15.8 0.0
Income tax expense 3.2 (14.6) 47.4
Net of tax (336.8) 43.1 14.1
Defined benefit plan and other postretirement liabilities      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Beginning balance (99.4) (95.6) (84.0)
Other comprehensive income (loss) before reclassifications (11.9) (10.1) (5.9)
Net amount reclassified to net income (loss) 6.7 6.3 (5.7)
Ending balance (104.6) (99.4) (95.6)
Unrealized gain (loss) on financial instruments      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Beginning balance 1.5 1.6 1.7
Other comprehensive income (loss) before reclassifications 0.0 0.0 0.0
Net amount reclassified to net income (loss) (0.2) (0.1) (0.1)
Ending balance 1.3 1.5 1.6
Accumulated other comprehensive loss      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Beginning balance (97.9) (94.0) (82.3)
Ending balance (103.3) (97.9) (94.0)
Reclassification out of Accumulated Other Comprehensive Income | Defined benefit plan and other postretirement liabilities      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Costs of goods sold (8.5) (1.0) 3.5
Other income, net 0.0 0.0 (8.9)
Selling, general and administrative expenses 1.1 (0.2) 3.3
Other operating expense (income), net 2.2 (2.6) (9.0)
Income tax expense 0.0 0.0 (0.3)
Net of tax (5.2) (3.8) (11.4)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gain (loss) on financial instruments      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Costs of goods sold (0.2) (0.1) (0.2)
Income tax expense 0.0 0.0 (0.1)
Net of tax $ (0.2) $ (0.1) $ (0.3)
[1]
(1) Including purchases from related party of $277.9 million, $181.4 million and $284.7 million for the years ended December 31, 2024, 2023 and 2022, respectively.
v3.25.0.1
Pension and Other Postretirement Benefits - Change in benefit obligation (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension      
Change in benefit obligation [Roll Forward]      
Benefit obligation at beginning of year $ 305.1 $ 263.0  
Service cost 4.0 3.3 $ 4.3
Interest cost 17.2 17.3 10.3
Plan amendments 0.0 1.1  
Actuarial (gain) loss (3.2) 11.0  
Medicare Part D 0.0 0.0  
Acquisition 0.0 28.6  
Benefits paid (21.4) (19.9)  
Exchange rates (0.4) (0.5)  
Plan participants' contributions 1.0 1.2  
Benefit obligation at end of year 302.3 305.1 263.0
OPEB      
Change in benefit obligation [Roll Forward]      
Benefit obligation at beginning of year 76.8 73.7  
Service cost 0.2 0.1 0.2
Interest cost 3.9 3.9 2.9
Plan amendments 0.0 0.0  
Actuarial (gain) loss 0.3 4.8  
Medicare Part D 0.2 0.3  
Acquisition 0.0 0.8  
Benefits paid (5.7) (6.8)  
Exchange rates 0.0 0.0  
Plan participants' contributions 0.0 0.0  
Benefit obligation at end of year $ 75.7 $ 76.8 $ 73.7
v3.25.0.1
Pension and Other Postretirement Benefits - Change in Plan Assets (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Pension    
Change in fair value of plan assets [Roll Forward]    
Fair value of plan assets at beginning of year $ 256.8 $ 216.6
Actual return on plan assets 6.8 21.4
Acquisition 0.0 31.5
Employer contributions 2.3 6.6
Medicare Part D subsidy received 0.0 0.0
Benefits paid (21.5) (19.9)
Exchange rates (0.3) (0.6)
Plan participants' contributions 1.0 1.2
Fair value of assets at end of year 245.1 256.8
OPEB    
Change in fair value of plan assets [Roll Forward]    
Fair value of plan assets at beginning of year 0.0 0.0
Actual return on plan assets 0.0 0.0
Acquisition 0.0 0.0
Employer contributions 5.5 6.5
Medicare Part D subsidy received 0.2 0.3
Benefits paid (5.7) (6.8)
Exchange rates 0.0 0.0
Plan participants' contributions 0.0
Fair value of assets at end of year $ 0.0 $ 0.0
v3.25.0.1
Pension and Other Postretirement Benefits - Funded status of plans (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Pension    
Defined Benefit Plan Disclosure [Line Items]    
Funded status $ (57.2) $ (48.3)
Current liabilities (1.8) (1.8)
Non-current liabilities (55.4) (46.5)
Net amount recognized (57.2) (48.3)
Net loss 82.3 82.1
Prior service cost (benefit) 1.6 1.8
Total 83.9 83.9
Projected benefit obligation for plans with accumulated benefit obligations in excess of plan assets 302.3 305.1
Accumulated benefit obligation for plans with accumulated benefit obligations in excess of plan assets 279.3 305.9
Fair value of plan assets for plans with accumulated benefit obligations in excess of plan assets 245.1 256.8
OPEB    
Defined Benefit Plan Disclosure [Line Items]    
Funded status (75.7) (76.8)
Current liabilities (6.5) (6.5)
Non-current liabilities (69.2) (70.3)
Net amount recognized (75.7) (76.8)
Net loss 14.4 14.8
Prior service cost (benefit) 0.0 0.0
Total $ 14.4 $ 14.8
v3.25.0.1
Pension and Other Postretirement Benefits - Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension      
Defined Benefit Plan Disclosure [Line Items]      
Service cost $ 4.0 $ 3.3 $ 4.3
Interest cost 17.2 17.3 10.3
Expected return on plan assets (18.3) (17.3) (23.5)
Amortization of prior service costs 0.2 0.1 0.1
Amortization of net loss 5.8 6.0 3.5
Net periodic benefit cost 8.9 9.4 (5.3)
Curtailment benefit 0.0 0.0 0.0
Total benefit cost 8.9 9.4 (5.3)
OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 0.2 0.1 0.2
Interest cost 3.9 3.9 2.9
Expected return on plan assets 0.0 0.0 0.0
Amortization of prior service costs 0.0 0.0 (1.3)
Amortization of net loss 0.7 0.1 1.3
Net periodic benefit cost 4.8 4.1 3.1
Curtailment benefit 0.0 0.0 (8.9)
Total benefit cost $ 4.8 $ 4.1 $ (5.8)
v3.25.0.1
Pension and Other Postretirement Benefits - Changes in Plan Assets & Benefit Obligation Recognized in OCI (pre-taxed) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]      
Net (gain) loss $ (11.9) $ (10.1) $ (5.9)
Amortization of prior service benefit during the period 0.2 0.1 (1.2)
Pension      
Defined Benefit Plan Disclosure [Line Items]      
Net (gain) loss (8.4) (6.9)  
Net loss (gain) transferred due to acquisition 0.0 (4.5)  
Prior service cost (benefit) 0.0 1.2  
Amortization of net loss, including recognition due to settlement (5.8) (6.0)  
Amortization of prior service benefit during the period 0.2 0.1  
Exchange rates (2.4) (1.1)  
Total amount recognized in other comprehensive income (loss) 0.0 (3.6)  
Net periodic benefit cost 8.9 9.4 (5.3)
Total recognized in net periodic benefit cost and other comprehensive income (loss) 8.9 5.8  
OPEB      
Defined Benefit Plan Disclosure [Line Items]      
Net (gain) loss (0.3) (4.8)  
Net loss (gain) transferred due to acquisition 0.0 (0.2)  
Prior service cost (benefit) 0.0 0.0  
Amortization of net loss, including recognition due to settlement (0.7) (0.2)  
Amortization of prior service benefit during the period 0.0 0.0  
Exchange rates 0.0 (0.1)  
Total amount recognized in other comprehensive income (loss) (0.4) 4.3  
Net periodic benefit cost 4.8 4.1 $ (5.8)
Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 4.4 $ 8.4  
v3.25.0.1
Pension and Other Postretirement Benefits - Weighted Average assumptions used in calculating benefit obligations (Details)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Pension    
Defined Benefit Plan Disclosure [Line Items]    
Discount rate 5.99% 5.19%
Measurement date Dec. 31, 2024 Dec. 31, 2023
Pension | United States    
Defined Benefit Plan Disclosure [Line Items]    
Rate of compensation increase 3.00% 3.50%
Pension | Jamaica    
Defined Benefit Plan Disclosure [Line Items]    
Rate of compensation increase 7.00%  
OPEB    
Defined Benefit Plan Disclosure [Line Items]    
Discount rate 5.62% 5.19%
Measurement date Dec. 31, 2024 Dec. 31, 2023
OPEB | United States    
Defined Benefit Plan Disclosure [Line Items]    
Rate of compensation increase 3.00% 3.50%
OPEB | Jamaica    
Defined Benefit Plan Disclosure [Line Items]    
Rate of compensation increase 7.00%  
v3.25.0.1
Pension and Other Postretirement Benefits - Weighted average assumptions used to determine net periodic benefit cost (Details)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Pension      
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]      
Measurement date 12/31/2023 12/31/2022 12/31/2021
Fiscal year end 12/31/2024 12/31/2023 12/31/2022
Discount rate 6.75% 5.50% 2.94%
Expected return on plan assets 7.28% 7.25% 7.25%
Pension | United States      
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]      
Rate of compensation increase, group 1 3.50% 4.00% 3.00%
Rate of compensation increase, group 2   3.50% 3.50%
Pension | Jamaica      
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]      
Rate of compensation increase, group 1 9.00%    
OPEB      
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]      
Measurement date 12/31/2023 12/31/2022 12/31/2021
Fiscal year end 12/31/2024 12/31/2023 12/31/2022
Discount rate 5.43% 5.57% 2.64%
Expected return on plan assets 0.00% 0.00% 0.00%
OPEB | United States      
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]      
Rate of compensation increase, group 1 3.50% 4.00% 3.00%
Rate of compensation increase, group 2   3.50% 3.50%
OPEB | Jamaica      
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]      
Rate of compensation increase, group 1 8.00%    
v3.25.0.1
Pension and Other Postretirement Benefits - Assumed health care trend rates (Details)
Dec. 31, 2024
United States  
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]  
Medical cost inflation, years 13 and thereafter 4.50%
Pre 65 | United States  
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]  
Medical cost inflation rate 8.50%
Pre 65 | Jamaica  
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]  
Medical cost inflation rate 8.00%
Post 65 | United States  
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]  
Medical cost inflation rate 7.50%
Post 65 | Jamaica  
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]  
Medical cost inflation rate 8.00%
v3.25.0.1
Pension and Other Postretirement Benefits - Pension Plan Asset Allocation (Details)
Dec. 31, 2024
Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]    
Target allocation percentage of assets 100.00%  
Actual plan asset allocations 100.00% 100.00%
Global equity    
Defined Benefit Plan Disclosure [Line Items]    
Target allocation percentage of assets 50.00%  
Actual plan asset allocations 51.00% 44.00%
Diversified credit    
Defined Benefit Plan Disclosure [Line Items]    
Target allocation percentage of assets 15.00%  
Actual plan asset allocations 17.00% 15.00%
Real assets    
Defined Benefit Plan Disclosure [Line Items]    
Target allocation percentage of assets 10.00%  
Actual plan asset allocations 11.00% 10.00%
Liability hedging assets    
Defined Benefit Plan Disclosure [Line Items]    
Target allocation percentage of assets 25.00%  
Actual plan asset allocations 20.00% 28.00%
Cash    
Defined Benefit Plan Disclosure [Line Items]    
Target allocation percentage of assets 0.00%  
Actual plan asset allocations 1.00% 3.00%
v3.25.0.1
Pension and Other Postretirement Benefits - Fair Value Hierarchy (Details) - Pension - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets $ 245.1 $ 256.8 $ 216.6
Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 32.6 31.4  
Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.6 0.6  
Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Assets measured at NAV      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 211.9 224.8  
Cash      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 3.5 5.0  
Cash | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.7 0.4  
Cash | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Cash | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Cash | Assets measured at NAV      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 2.8 4.6  
Global equity      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 128.1 119.7  
Global equity | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 20.0 19.7  
Global equity | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Global equity | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Global equity | Assets measured at NAV      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 108.1 100.0  
Diversified credit      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 47.1 45.9  
Diversified credit | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 11.8 11.2  
Diversified credit | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Diversified credit | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Diversified credit | Assets measured at NAV      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 35.3 34.7  
Real assets      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 23.1 22.8  
Real assets | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Real assets | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0    
Real assets | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Real assets | Assets measured at NAV      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 23.1 22.8  
Liability hedging assets      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 42.6 62.7  
Liability hedging assets | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Liability hedging assets | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Liability hedging assets | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Liability hedging assets | Assets measured at NAV      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 42.6 62.7  
Other      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.7 0.7  
Other | Level 1      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.1 0.1  
Other | Level 2      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.6 0.6  
Other | Level 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets 0.0 0.0  
Other | Assets measured at NAV      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of assets $ 0.0 $ 0.0  
v3.25.0.1
Pension and Other Postretirement Benefits - Expected Contribution Cash Flows (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Pension    
Defined Benefit Plan Disclosure [Line Items]    
Employer contributions $ 2.3 $ 6.6
Expected contributions in next twelve months 8.0  
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]    
2025 20.5  
2026 20.9  
2027 20.9  
2028 21.4  
2029 21.7  
2030 – 2034 94.8  
OPEB    
Defined Benefit Plan Disclosure [Line Items]    
Employer contributions 5.5 $ 6.5
Expected contributions in next twelve months 6.4  
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]    
2025 6.5  
2026 6.5  
2027 6.5  
2028 6.7  
2029 6.5  
2030 – 2034 $ 30.9  
v3.25.0.1
Pension and Other Postretirement Benefits - Participation in Multi-Employer Pension Plans (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Retirement Benefits [Abstract]        
EIN 236648508      
PN 499      
Pension protection act zone status     Green Green
Subject to financial improvement/rehabilitation plan No      
Contributions of century aluminum company $ 40 $ 200 $ 1,600  
Withdrawal from Plan Probable No      
Surcharge Imposed No      
Expiration date of collective bargaining agreement Mar. 31, 2026      
v3.25.0.1
Pension and Other Postretirement Benefits - Company matching contribution to defined contribution 401(K) plans (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Retirement Benefits [Abstract]      
Age requirement for future accruals 50 years    
Company matching contribution to defined contribution (401(k)) plans $ 6.3 $ 5.8 $ 6.0
v3.25.0.1
Share-based Compensation (Details)
$ in Millions
 12 Months Ended
Dec. 31, 2024
USD ($)
award_type
shares
Dec. 31, 2023
USD ($)
Amended and Restated Stock Option Plan    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share based compensation, vesting rights (in time period) 3 years  
Shares authorized (in shares) 12,900,000  
Shares remaining (in shares) 2,673,311  
Amended and Restated Stock Option Plan | Non-employee director    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share based compensation, vesting rights (in time period) 12 months  
Long Term Incentive Plan    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share based compensation, vesting rights (in time period) 3 years  
Number of award types provided | award_type 2  
Performance unit liability | $ $ 7.1 $ 3.3
v3.25.0.1
Share-based Compensation - Service Based Awards Rollforward (Details)
 12 Months Ended
Dec. 31, 2024
shares
Service-Based Share Awards  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]  
Service-based share awards outstanding, beginning of period (in shares) 1,156,774
Granted (in shares) 650,755
Vested (in shares) (263,227)
Forfeited (in shares) (139,407)
Service-based share awards outstanding, end of period (in shares) 1,404,895
Performance-based share awards  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]  
Service-based share awards outstanding, beginning of period (in shares) 602,564
Granted (in shares) 475,226
Vested (in shares) (303,315)
Forfeited (in shares) 0
Service-based share awards outstanding, end of period (in shares) 774,475
v3.25.0.1
Share-based Compensation - Service-Based Awards, Additional disclosures (Details) - $ / shares
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Service-Based Awards, Additional disclosures [Abstract]      
Weighted average per share fair value of service-based share grants (in dollars per share) $ 10.11 $ 12.58 $ 17.30
v3.25.0.1
Share-based Compensation - Share and performance-based compensation expense (Details) - USD ($)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Share and performance-based compensation expense [Abstract]      
Performance-based share (benefit) expense $ 9,300,000 $ 2,000,000.0 $ (5,000,000.0)
Service-based share expense 6,100,000 4,600,000 4,400,000
Total share-based compensation (benefit) expense before income tax 15,400,000 6,600,000 (600,000)
Income tax 0 0 0
Total share-based compensation (benefit) expense, net of income tax 15,400,000 6,600,000 (600,000)
Share-based payment arrangement, amount capitalized 0 $ 0 $ 0
Unrecognized compensation expense $ 13,200,000    
Weighted average period of expense recognition 1 year 8 months 12 days    
v3.25.0.1
Earnings Per Share - Schedule of EPS (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Earnings Per Share [Abstract]      
Net income attributable to Century stockholders $ 336.8 $ (43.1) $ (14.1)
Less: net income allocated to participating securities 17.9 $ 0.0 $ 0.0
Amount allocated to common stockholders   100.00% 100.00%
Basic EPS:      
Net income (loss) allocated to common stockholders $ 318.9 $ (43.1) $ (14.1)
Net income (loss) allocated to common stockholders (in shares) 92.8 92.4 91.4
Net income (loss) allocated to common stockholders (in dollars per share) $ 3.44 $ (0.47) $ (0.15)
Effect of Dilutive Securities      
Share-based compensation $ 0.0    
Share-based compensation (in shares) 1.0    
Convertible senior notes $ 2.7    
Convertible senior notes (in shares) 4.6    
Diluted EPS:      
Net income (loss) allocated to common stockholders $ 321.6 $ (43.1) $ (14.1)
Net income (loss) allocated to common stockholders (in shares) 98.4 92.4 91.4
Net income (loss) allocated to common stockholders (in dollars per share) $ 3.27 $ (0.47) $ (0.15)
v3.25.0.1
Earnings Per Share - Securities Excluded (Details) - shares
shares in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Share-based compensation      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Share based compensation (in shares) 0.6 1.0 1.7
Convertible preferred shares      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Share based compensation (in shares) 5.2 5.4 5.8
Convertible senior notes      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Share based compensation (in shares) 0.0 4.6 4.6
v3.25.0.1
Income Taxes - Components of Pre-tax Book Income (Loss) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Income Tax Disclosure [Abstract]      
U.S. $ 335.5 $ 78.0 $ (193.6)
Foreign  (11.7) (144.8) 227.0
Income (loss) before income taxes $ 323.8 $ (66.8) $ 33.4
v3.25.0.1
Income Taxes - Significant Components of Income Tax Expense (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Current:      
U.S. federal current expense (benefit) $ 0.0 $ 0.5 $ 0.0
State current expense (benefit) 0.0 0.0 0.2
Foreign current expense (benefit) 4.9 15.8 4.0
Total current expense (benefit) 4.9 16.3 4.2
Deferred:      
U.S. federal deferred benefit 0.0 (0.3) (0.3)
State deferred benefit 0.0 (0.1) 0.0
Foreign deferred tax (benefit) expense (1.7) (30.5) 43.5
Total deferred (benefit) expense (1.7) (30.9) 43.2
Total income tax (benefit) expense $ 3.2 $ (14.6) $ 47.4
v3.25.0.1
Income Taxes - Reconciliation of statutory to effective income tax rate (Details)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Effective Income Tax Rate Reconciliation, Amount [Abstract]      
Federal Statutory Rate 21.00% 21.00% 21.00%
Permanent differences 1.00% 1.10% (15.20%)
State taxes, net of Federal benefit 0.00% (0.10%) 0.10%
Rate change (0.50%) (0.30%) 0.40%
Foreign earnings taxed at different rates than U.S. 0.00% 2.00% (0.80%)
Valuation allowance (11.30%) 3.60% (4.20%)
Foreign dividends and inclusions 0.50% (12.70%) 122.90%
Net operating loss expiration and remeasurement 2.80% (8.00%) 43.10%
Filing differences 8.70% 0.60% (19.10%)
Changes in uncertain tax reserves 0.20% (1.30%) (5.30%)
Advanced Manufacturing Production Credit (5.90%) 18.60% 0.00%
Bargain Purchase gain (0.157) 0 0
Other 0.20% (2.70%) (0.90%)
Effective tax rate 1.00% 21.80% 142.00%
v3.25.0.1
Income Taxes - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Tax Credit Carryforward [Line Items]      
Reduction in cost of goods sold [1] $ (2,035,300,000) $ (2,093,500,000) $ (2,730,600,000)
Reduction in selling, general and administrative expenses (56,800,000) (44,300,000) $ (37,500,000)
Manufacturing credit receivable 81,500,000 59,300,000  
Manufacturing credit receivable - less current portion 70,400,000 0  
Valuation allowance (504,400,000) (537,600,000)  
Unrecognized tax benefits that would impact effective tax rate 1,400,000    
Inflation Reduction Act      
Tax Credit Carryforward [Line Items]      
Reduction in cost of goods sold 89,700,000 56,500,000  
Reduction in selling, general and administrative expenses $ 2,900,000 $ 2,800,000  
[1]
(1) Including purchases from related party of $277.9 million, $181.4 million and $284.7 million for the years ended December 31, 2024, 2023 and 2022, respectively.
v3.25.0.1
Income Taxes - Significant Components of our deferred tax assets & liabilities (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Deferred tax assets:    
Accrued postretirement benefit cost $ 30.1 $ 30.7
Net operating losses 473.3 467.6
Disallowed interest expense 37.1 29.2
Derivative and hedging contracts 0.1 1.2
Fixed asset tax over book basis 0.0 9.2
Other 29.4 28.3
Total deferred tax assets 570.0 566.2
Valuation allowance (504.4) (537.6)
Net deferred tax assets 65.6 28.6
Deferred tax liabilities:    
Fixed asset book over tax basis (115.9) (62.0)
Derivatives 0.0 0.0
Foreign basis differences 0.6 (18.1)
Other (21.4) (20.6)
Total deferred tax liabilities (136.7) (100.7)
Net deferred tax liability $ (71.1) $ (72.1)
v3.25.0.1
Income Taxes - Changes in Valuation Allowance (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance, valuation allowance $ 537.6 $ 487.9 $ 485.8
Remeasurement of deferred tax assets 0.0 0.0 0.0
Release of valuation allowance 0.0 0.0 0.0
Expiration of net operating losses (6.1) (7.2) (15.4)
Other change in valuation allowance (27.1) 56.9 17.5
Balance, valuation allowance $ 504.4 $ 537.6 $ 487.9
v3.25.0.1
Income Taxes - Net Operating Losses Carryforwards (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Federal    
Operating Loss Carryforwards [Line Items]    
Operating loss carryforwards $ 1,571.2 $ 1,533.5
State    
Operating Loss Carryforwards [Line Items]    
Operating loss carryforwards 1,163.5 1,221.0
Foreign    
Operating Loss Carryforwards [Line Items]    
Operating loss carryforwards $ 342.2 $ 344.4
v3.25.0.1
Income Taxes - Gross Unrecognized Tax Positions (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]      
Balance as of January 1,   $ 3.0 $ 2.2 $ 4.0
Additions based on tax positions related to the current year 0.6 1.3 0.3
Decreases due to lapse of applicable statute of limitations (0.1) (0.5) (2.1)
Balance as of December 31, $ 3.5 $ 3.0 $ 2.2
v3.25.0.1
Commitments and Contingencies (Details)
$ in Millions
 1 Months Ended 12 Months Ended
Oct. 01, 2021
USD ($)
Aug. 18, 2017
USD ($)
Sep. 30, 2017
USD ($)
Dec. 31, 2024
USD ($)
laborUnion
MW
Dec. 31, 2013
USD ($)
Labor Commitments [Abstract]          
Percentage of total work force in union       59.00%  
Percentage of Grundartangi work force represented by the labor unions       86.00%  
Number of labor unions Grundartangi subsidiary entered into a new labor agreement with | laborUnion       5  
Percentage of domestic based work force represented by a union       39.00%  
Percentage of foreign work force represented by union       0.61  
Contingent consideration, accrued interest and principal       $ 32.3  
E.ON Contingent Obligation | Long-term Debt          
Labor Commitments [Abstract]          
Stated interest rate, percentage       10.94%  
Netherlands          
Labor Commitments [Abstract]          
Percentage of total work force in union       100.00%  
Pension Benefit Guarantee Corporation          
PBGC Settlement [Abstract]          
Required pension contributions above minimum         $ 17.4
Pension contributions, amended term, annual contribution $ 2.4        
Pension contributions, amended term, total contribution $ 9.6     $ 7.2  
Pension contributions, term 4 years        
Kenergy | Century Marketer, LLC          
Power Contingencies [Abstract]          
Extension term       1 year  
Required termination period       1 year  
Hawesville | Kenergy          
Power Contingencies [Abstract]          
Extension term       1 year  
Required termination period       1 year  
Sebree | Kenergy          
Power Contingencies [Abstract]          
Extension term       1 year  
Required termination period       1 year  
Santee Cooper          
Power Contingencies [Abstract]          
Power agreement, power supply, percentage       100.00%  
Grundartangi - HS, Landsvirkjun          
Power Contingencies [Abstract]          
Power currently available under the power purchase agreement, available (in megawatts) | MW       545  
Grundartangi - Landsvirkjun          
Power Contingencies [Abstract]          
Power currently available under the power purchase agreement, available (in megawatts) | MW       25  
Ravenswood Retiree Medical Benefits Changes          
Ravenswood litigation [Abstract]          
Litigation settlement amount   $ 23.0      
Ravenswood litigation settlement installment period   10 years      
Litigation payment to trust     $ 5.0    
Gain (loss) related to litigation settlement     5.5    
Loss contingency accrual     $ 12.5    
Litigation settlement, annual installment       $ 2.0  
Litigation settlement installment period       9 years  
Other current liabilities       $ 2.0  
Other liabilities       $ 1.6  
v3.25.0.1
Asset Retirement Obligations (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Asset Retirement Obligation [Roll Forward]    
Beginning balance $ 51.1 $ 21.2
Additional ARO liabilities incurred 6.7 3.1
ARO liabilities settled (4.6) (1.5)
Accretion expense 2.1 2.0
Acquired ARO liabilities 0.0 23.9
Revisions in estimated cash flows 10.8 2.4
Ending balance 66.1 51.1
Current portion of asset retirement obligations 4.6 1.6
Asset retirement obligations - less current portion $ 61.5 $ 49.5
v3.25.0.1
Business Segments (Details)
 12 Months Ended
Dec. 31, 2024
segment
smelter
Dec. 31, 2023
Dec. 31, 2022
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]      
Number of primary aluminum smelters | smelter 3    
Number of operating segments 4    
Number of reportable segments 1    
Customer Concentration Risk | Sales Revenue | One Customer      
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]      
Concentration risk, percentage 10.00% 10.00%  
Customer Concentration Risk | Sales Revenue | Two Customers      
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]      
Concentration risk, percentage     10.00%
Bauxite Mining and Alumina Refinery Joint Venture      
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]      
Ownership percentage 55.00%    
v3.25.0.1
Business Segments - Segment Assets (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Segment Reporting, Asset Reconciling Item [Line Items]      
TOTAL $ 1,939.4 $ 1,846.5 $ 1,472.0
Capital expenditures 82.3 95.0 86.3
Aluminum      
Segment Reporting, Asset Reconciling Item [Line Items]      
TOTAL 1,896.6 1,808.1 1,432.4
Corporate, unallocated      
Segment Reporting, Asset Reconciling Item [Line Items]      
TOTAL $ 42.8 $ 38.4 $ 39.6
v3.25.0.1
Business Segments - Geography, Segment Reporting (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Revenues from External Customers and Long-Lived Assets [Line Items]      
Total Net sales $ 2,220.3 $ 2,185.4 $ 2,777.3
United States      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Total Net sales 1,427.0 1,358.6 1,737.2
Long-lived assets 233.6 219.1 244.9
Iceland      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Total Net sales 793.3 826.8 1,040.1
Long-lived assets 526.4 529.4 491.0
Jamaica      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Long-lived assets 255.2 275.8 0.0
Other      
Revenues from External Customers and Long-Lived Assets [Line Items]      
Long-lived assets $ 50.6 $ 55.1 $ 58.3
v3.25.0.1
Business Segments - Major Customers (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Glencore      
Revenue, Major Customer [Line Items]      
Revenues $ 1,312.1 $ 1,612.1 $ 1,671.1
Southwire      
Revenue, Major Customer [Line Items]      
Revenues $ 0.0 $ 0.0 $ 331.3
v3.25.0.1
Business Segments - Reconciliation of Net Income (Loss) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Total net sales $ 2,220.3 $ 2,185.4 $ 2,777.3
Segment Cost of goods sold [1] 2,035.3 2,093.5 2,730.6
Asset impairment 0.0 0.0 159.4
Depreciation, depletion and amortization 81.8 74.7 73.4
Selling, general and administrative expenses 56.8 44.3 37.5
Interest income 2.1 2.0 0.5
Net gain (loss) on forward and derivative contracts - nonaffiliates 2.0 61.8 197.2
Bargain purchase gain 245.9 0.0 0.0
Other income, net (4.5) (3.3) 15.3
Income tax benefit (expense) (3.2) 14.6 (47.4)
Net Income (loss) 320.7 (52.3) (14.1)
Net loss attributable to noncontrolling interests 16.1 9.2 0.0
Net income (loss) attributable to Century stockholders 336.8 (43.1) (14.1)
Related Party      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Total net sales 1,312.1 1,612.1 1,671.1
Segment Cost of goods sold 277.9 181.4 284.7
Interest expense (6.7) (1.8) 0.0
Net gain (loss) on forward and derivative contracts - nonaffiliates (0.5) 0.6 (13.3)
Nonrelated Party      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Total net sales 908.2 573.3 1,106.2
Interest expense (36.4) (33.7) (29.3)
Net gain (loss) on forward and derivative contracts - nonaffiliates 2.5 (62.4) 210.4
Reportable Segment      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Total net sales 2,220.3 2,185.4 2,777.3
Segment Cost of goods sold (2,014.7) (2,056.9) (2,597.0)
IRA Credit - Cost of goods sold 89.7 56.5 0.0
Asset impairment 0.0 0.0 (159.4)
Other segment items (25.4) (55.7) (12.9)
Segment EBITDA 269.9 129.3 8.0
Depreciation, depletion and amortization (86.5) (80.7) (76.4)
Selling, general and administrative expenses (56.8) (44.3) (37.5)
Interest income 2.1 2.0 0.5
Bargain purchase gain 245.9 0.0 0.0
Other income, net (9.7) 24.1 (29.1)
Income tax benefit (expense) (3.2) 14.6 (47.4)
Net Income (loss) 320.6 (52.3) (14.1)
Net loss attributable to noncontrolling interests 16.2 9.2 0.0
Net income (loss) attributable to Century stockholders 336.8 (43.1) (14.1)
Reportable Segment | Related Party      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Interest expense (6.7) (1.8) 0.0
Net gain (loss) on forward and derivative contracts - nonaffiliates (0.5) 0.6 (13.3)
Reportable Segment | Nonrelated Party      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]      
Interest expense (36.4) (33.7) (29.3)
Net gain (loss) on forward and derivative contracts - nonaffiliates $ 2.5 $ (62.4) $ 210.4
[1]
(1) Including purchases from related party of $277.9 million, $181.4 million and $284.7 million for the years ended December 31, 2024, 2023 and 2022, respectively.
v3.25.0.1
Derivatives - Narrative (Details)
 12 Months Ended
Dec. 31, 2024
DKK (kr)
Boe
MMBTU
MWh
t
Dec. 31, 2024
USD ($)
Dec. 31, 2023
USD ($)
Supply Commitment [Line Items]      
Restricted cash | $   $ 0 $ 0
LME forward financial sales contracts      
Supply Commitment [Line Items]      
Open position to offset fixed prices 32,000    
Fixed to Variable Midwest Premium Swap      
Supply Commitment [Line Items]      
Open position to offset fixed prices 32,000    
Fixed to Floating Swap      
Supply Commitment [Line Items]      
Open position to offset fixed prices 0    
USD ISK Forward Swap      
Supply Commitment [Line Items]      
Derivative, forward contracts | kr kr 0    
Henry Hub Natural Gas Price Swaps      
Supply Commitment [Line Items]      
Derivative liability, energy | MMBTU 0    
HFO Price Swaps      
Supply Commitment [Line Items]      
Derivative liability, energy | Boe 295,000    
Indiana Hub Power Price Swaps      
Supply Commitment [Line Items]      
Derivative liability, energy | MWh 591,192    
v3.25.0.1
Derivative - Assets and Liabilities (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Related Party    
Derivative [Line Items]    
Due to affiliates $ 109.3 $ 101.4
Commodity Contract | Related Party    
Derivative [Line Items]    
Due to affiliates 0.0 6.4
Not Designated as Hedging Instrument    
Derivative [Line Items]    
Asset Fair Value 4.5 2.9
Liability Fair Value 4.4 7.9
Not Designated as Hedging Instrument | Commodity Contract    
Derivative [Line Items]    
Asset Fair Value 4.5 2.9
Liability Fair Value 4.4 7.8
Not Designated as Hedging Instrument | Foreign Exchange Contract    
Derivative [Line Items]    
Asset Fair Value 0.0 0.0
Liability Fair Value $ 0.0 $ 0.1
v3.25.0.1
Derivative - Net Gain (Loss) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Derivative [Line Items]      
Net gain (loss) on forward and derivative contracts - nonaffiliates $ 2.0 $ 61.8 $ 197.2
Commodity Contract      
Derivative [Line Items]      
Net gain (loss) on forward and derivative contracts - nonaffiliates 2.1 63.5 206.6
Commodity Contract | Glencore      
Derivative [Line Items]      
Net gain (loss) on forward and derivative contracts - nonaffiliates (0.5) 0.6 (13.3)
Foreign Exchange Contract      
Derivative [Line Items]      
Net gain (loss) on forward and derivative contracts - nonaffiliates $ (0.1) $ (1.7) $ (9.4)
v3.25.0.1
Variable Interest Entity - Schedule of Consolidated VIE's Assets and Liabilities (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
ASSETS      
Cash and cash equivalents $ 32.9 $ 88.8  
Accounts receivable - net 75.8 53.7  
Non-trade receivables 13.2 36.2  
Inventories 539.0 477.0  
Prepaid and other current assets 28.3 27.5  
Total current assets 802.8 767.1  
Property, plant and equipment - net 978.3 1,004.2  
Other assets 87.9 75.2  
TOTAL 1,939.4 1,846.5 $ 1,472.0
LIABILITIES      
Accounts payable, trade 187.3 249.5  
Accrued compensation and benefits 49.8 38.1  
Accrued and other current liabilities 42.0 50.9  
Total current liabilities 463.7 763.0  
Accrued benefits costs - less current portion 130.4 120.3  
Other liabilities 92.6 66.3  
Asset retirement obligations - less current portion 61.5 49.5  
Total noncurrent liabilities 813.0 739.4  
Variable Interest Entity, Primary Beneficiary      
ASSETS      
Cash and cash equivalents 17.4 7.4  
Accounts receivable - net 1.1 0.0  
Non-trade receivables 13.1 38.3  
Inventories 109.8 96.6  
Prepaid and other current assets 2.0 8.7  
Total current assets 218.5 227.7  
Property, plant and equipment - net 232.1 248.7  
Other assets 23.1 27.1  
TOTAL 473.7 503.5  
LIABILITIES      
Accounts payable, trade 39.1 73.1  
Accrued compensation and benefits 8.5 2.3  
Accrued and other current liabilities 7.2 7.1  
Total current liabilities 104.4 137.9  
Accrued benefits costs - less current portion 17.7 0.8  
Other liabilities 66.7 36.1  
Asset retirement obligations - less current portion 35.0 26.0  
Total noncurrent liabilities 119.4 62.9  
TOTAL 223.8 200.8  
Variable Interest Entity, Primary Beneficiary | Related Party      
ASSETS      
Due from affiliates 75.1 76.7  
LIABILITIES      
Due to affiliates $ 49.6 $ 55.4