CENTURY ALUMINUM CO, 10-Q filed on 8/7/2025
Quarterly Report
v3.25.2
Cover - shares
 6 Months Ended
Jun. 30, 2025
Aug. 05, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2025  
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, Address Line Two Suite 1000  
Entity Address, City or Town Chicago  
Entity Address, State or Province IL  
Entity Address, Postal Zip Code 60606  
City Area Code 312  
Local Phone Number 696-3101  
Title of 12(b) Security Common Stock, $0.01 par value per share  
Entity Trading Symbol CENX  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding (in shares)   93,339,121
Entity Central Index Key 0000949157  
Amendment Flag false  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --12-31  
v3.25.2
CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)
shares in Millions, $ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Net sales        
Total net sales $ 628.1 $ 560.8 $ 1,262.0 $ 1,050.3
Cost of goods sold 591.9 540.4 1,165.2 [1] 1,013.4 [1]
Gross profit 36.2 20.4 96.8 36.9
Selling, general and administrative expenses 14.0 12.3 26.5 26.4
Other operating expenses - net 1.5 1.7 3.5 2.2
Operating income 20.7 6.4 66.8 8.3
Interest income 1.9 0.6 3.7 1.3
Bargain purchase gain 0.0 0.0 0.0 245.9
Other (loss) income - net (5.7) 1.1 (9.1) (0.4)
(Loss) income before income taxes (10.4) (6.2) 16.9 239.0
Income tax benefit (expense) 1.3 (0.5) (0.3) (1.0)
Net (loss) income (9.1) (6.7) 16.6 238.0
Net loss attributable to noncontrolling interests (4.5) (4.2) (8.5) (6.3)
Net (loss) income attributable to Century stockholders (4.6) (2.5) 25.1 244.3
Less: net income allocated to participating securities 0.0 0.0 1.3 13.0
Net (loss) income allocated to common stockholders $ (4.6) $ (2.5) $ 23.8 $ 231.3
Net (loss) income attributable to Century stockholders per common share:        
Basic (in dollars per share) $ (0.05) $ (0.03) $ 0.26 $ 2.50
Diluted (in dollars per share) $ (0.05) $ (0.03) $ 0.25 $ 2.24
Weighted-average common shares outstanding:        
Basic (in shares) 93.3 92.7 93.3 92.7
Diluted (in shares) 93.3 92.7 94.6 98.8
Related Party        
Net sales        
Total net sales $ 367.6 $ 324.2 $ 746.3 $ 639.2
Cost of goods sold 51.8 56.2 140.1 115.2
Interest expense (1.9) (1.4) (3.7) (3.3)
Net (loss) gain on forward and derivative contracts 0.0 (1.9) 0.0 2.5
Nonrelated Party        
Net sales        
Total net sales 260.5 236.6 515.7 411.1
Interest expense (9.8) (8.9) (19.8) (16.2)
Net (loss) gain on forward and derivative contracts $ (15.6) $ (2.1) $ (21.0) $ 0.9
[1]
(1) Purchases from related party were $51.8 million and $56.2 million for the three months ended June 30, 2025 and 2024, respectively. Purchases from related parties were $140.1 million and $115.2 million for the six months ended June 30, 2025 and 2024, respectively.
v3.25.2
CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Comprehensive (loss) income:        
Net (loss) income $ (9.1) $ (6.7) $ 16.6 $ 238.0
Other comprehensive income (loss) before income tax effect:        
Net loss on foreign currency cash flow hedges reclassified as income (0.1) 0.0 (0.1) (0.1)
Defined benefit plans and other postretirement benefits:        
Net loss arising during the period 0.0 0.0 0.0 (3.4)
Amortization of prior service (cost) benefit during the period 0.0 (0.1) 0.1 0.0
Amortization of net loss during the period 1.6 1.6 3.2 3.3
Other comprehensive income (loss) before income tax effect 1.5 1.5 3.2 (0.2)
Income tax effect 0.0 0.0 0.0 0.0
Other comprehensive income (loss) 1.5 1.5 3.2 (0.2)
Comprehensive (loss) income (7.6) (5.2) 19.8 237.8
Comprehensive loss attributable to noncontrolling interests (4.5) (4.2) (8.5) (6.3)
Comprehensive (loss) income attributable to Century stockholders $ (3.1) $ (1.0) $ 28.3 $ 244.1
v3.25.2
CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
ASSETS    
Cash and cash equivalents $ 40.7 $ 32.9
Restricted cash 2.8 2.8
Accounts receivable - net 108.2 75.8
Non-trade receivables 0.0 13.2
Manufacturing credit receivable 81.5 81.5
Inventories 513.4 539.0
Derivative assets 4.4 4.2
Prepaid and other current assets 25.5 28.3
Total current assets 790.3 802.8
Property, plant and equipment - net 975.6 978.3
Manufacturing credit receivable - less current portion 113.5 70.4
Other assets 69.6 87.9
Total assets 1,949.0 1,939.4
LIABILITIES:    
Accounts payable, trade 197.7 187.3
Non-trade payable 7.7 0.0
Accrued compensation and benefits 44.2 49.8
Accrued and other current liabilities 44.9 42.0
Derivative liabilities 19.4 4.4
Total current liabilities 451.1 463.7
Accrued benefits costs - less current portion 127.8 130.4
Other liabilities 96.8 92.6
Deferred taxes 73.5 71.2
Asset retirement obligations - less current portion 63.2 61.5
Total noncurrent liabilities 813.6 813.0
COMMITMENTS AND CONTINGENCIES (NOTE 12)
SHAREHOLDERS’ EQUITY:    
Preferred stock (Note 13) 0.0 0.0
Common stock (Note 13) 1.0 1.0
Additional paid-in capital 2,552.0 2,550.2
Treasury stock, at cost (86.3) (86.3)
Accumulated other comprehensive loss (100.1) (103.3)
Accumulated deficit (1,642.2) (1,667.2)
Total Century shareholders’ equity 724.4 694.4
Noncontrolling interests (40.1) (31.7)
Total equity 684.3 662.7
Total liabilities and equity 1,949.0 1,939.4
Related Party    
ASSETS    
Due from affiliates 13.8 25.1
LIABILITIES:    
Due to affiliates 100.7 109.3
Long-term debt 10.0 10.0
Nonrelated Party    
LIABILITIES:    
Current maturities of long-term debt 36.5 70.9
Long-term debt $ 442.3 $ 447.3
v3.25.2
CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
CASH FLOWS FROM OPERATING ACTIVITIES:    
Net income $ 16.6 $ 238.0
Adjustments to reconcile net income to net cash provided by (used in) operating activities:    
Unrealized loss (gain) on derivative instruments 14.5 (3.7)
Depreciation, depletion and amortization 41.4 41.7
Change in deferred tax provision 2.4 0.6
Bargain purchase gain 0.0 (245.9)
Other non-cash items - net 6.6 (1.8)
Change in operating assets and liabilities:    
Accounts receivable (15.2) (37.4)
Non-trade receivables 11.6 (1.6)
Manufacturing credit receivable (43.1) (23.8)
Due from affiliates 11.3 12.8
Inventories 27.5 9.4
Prepaid and other current assets 3.5 10.0
Accounts payable, trade 18.0 (13.4)
Due to affiliates (11.8) 8.8
Accrued and other current liabilities (3.9) (0.5)
Other - net 0.8 3.5
Net cash provided by (used in) operating activities 80.2 (3.3)
CASH FLOWS FROM INVESTING ACTIVITIES:    
Purchase of property, plant and equipment (45.0) (46.6)
Proceeds for joint venture partner's share of co-tenancy assets 11.4 0.0
Proceeds from sale of assets 0.0 2.3
Net cash used in investing activities (33.6) (44.3)
CASH FLOWS FROM FINANCING ACTIVITIES:    
Net cash (used in) provided by financing activities (38.8) 0.1
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH 7.8 (47.5)
Cash, cash equivalents and restricted cash, beginning of period 35.7 90.3
Cash, cash equivalents and restricted cash, end of period 43.5 42.8
Cash paid for:    
Interest 18.7 16.6
Taxes, net of refunds (0.1) 3.8
Non-cash investing activities:    
Capital expenditures 6.4 5.9
Capitalized interest 0.0 3.4
Distribution of property, plant and equipment to NCI 2.6 8.3
U.S. and Iceland Revolving Credit Facilities    
CASH FLOWS FROM FINANCING ACTIVITIES:    
Borrowings under revolving credit facilities 586.7 297.9
Repayments under facilities (621.0) (321.6)
Iceland Term Facility    
CASH FLOWS FROM FINANCING ACTIVITIES:    
Repayments under facilities 0.0 (1.2)
Casthouse Facility    
CASH FLOWS FROM FINANCING ACTIVITIES:    
Borrowings under Grundartangi casthouse debt facility 0.0 25.0
Repayments under Grundartangi casthouse debt facility $ (4.5) $ 0.0
v3.25.2
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, 2023     52,284            
Beginning 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)
Beginning balance (in shares) at Dec. 31, 2023       92,689,864          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Net income (loss) 238.0 244.3           244.3 (6.3)
Other comprehensive (loss) income (0.2) (0.2)         (0.2)    
Share-based compensation (in shares)       44,663          
Share-based compensation 1.8 1.8     1.8        
Conversion of preferred stock to common stock (in shares)     46 4,562          
Noncontrolling interest (0.8)               (0.8)
Ending balance (in shares) at Jun. 30, 2024     52,238            
Ending balance at Jun. 30, 2024 582.9 601.5 $ 0.0 $ 1.0 2,544.7 (86.3) (98.1) (1,759.8) (18.6)
Ending balance (in shares) at Jun. 30, 2024       92,739,089          
Beginning balance (in shares) at Mar. 31, 2024     52,238            
Beginning balance at Mar. 31, 2024 587.1 601.5 $ 0.0 $ 1.0 2,543.7 (86.3) (99.6) (1,757.3) (14.4)
Beginning balance (in shares) at Mar. 31, 2024       92,700,495          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Net income (loss) (6.7) (2.5)           (2.5) (4.2)
Other comprehensive (loss) income 1.5 1.5         1.5    
Share-based compensation (in shares)       38,594          
Share-based compensation 1.0 1.0     1.0        
Ending balance (in shares) at Jun. 30, 2024     52,238            
Ending balance at Jun. 30, 2024 582.9 601.5 $ 0.0 $ 1.0 2,544.7 (86.3) (98.1) (1,759.8) (18.6)
Ending balance (in shares) at Jun. 30, 2024       92,739,089          
Beginning balance (in shares) at Dec. 31, 2024     49,715            
Beginning 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)
Beginning balance (in shares) at Dec. 31, 2024 93,288,565     93,288,565          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Net income (loss) $ 16.6 25.1           25.1 (8.5)
Other comprehensive (loss) income 3.2 3.2         3.2    
Share-based compensation (in shares)       30,486          
Share-based compensation 1.8 1.8     1.8        
Conversion of preferred stock to common stock (in shares)     201 20,070          
Ending balance (in shares) at Jun. 30, 2025     49,514            
Ending balance at Jun. 30, 2025 $ 684.3 724.4 $ 0.0 $ 1.0 2,552.0 (86.3) (100.1) (1,642.2) (40.1)
Ending balance (in shares) at Jun. 30, 2025 93,339,121     93,339,121          
Beginning balance (in shares) at Mar. 31, 2025     49,679            
Beginning balance at Mar. 31, 2025 $ 690.7 726.3 $ 0.0 $ 1.0 2,550.8 (86.3) (101.6) (1,637.6) (35.6)
Beginning balance (in shares) at Mar. 31, 2025       93,296,937          
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Net income (loss) (9.1) (4.6)           (4.6) (4.5)
Other comprehensive (loss) income 1.5 1.5         1.5    
Share-based compensation (in shares)       25,707          
Share-based compensation 1.2 1.2     1.2        
Conversion of preferred stock to common stock (in shares)     165 16,477          
Ending balance (in shares) at Jun. 30, 2025     49,514            
Ending balance at Jun. 30, 2025 $ 684.3 $ 724.4 $ 0.0 $ 1.0 $ 2,552.0 $ (86.3) $ (100.1) $ (1,642.2) $ (40.1)
Ending balance (in shares) at Jun. 30, 2025 93,339,121     93,339,121          
v3.25.2
CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Cost of goods sold $ 591.9 $ 540.4 $ 1,165.2 [1] $ 1,013.4 [1]
Related Party        
Cost of goods sold $ 51.8 $ 56.2 $ 140.1 $ 115.2
[1]
(1) Purchases from related party were $51.8 million and $56.2 million for the three months ended June 30, 2025 and 2024, respectively. Purchases from related parties were $140.1 million and $115.2 million for the six months ended June 30, 2025 and 2024, respectively.
v3.25.2
General
 6 Months Ended
Jun. 30, 2025
Accounting Policies [Abstract]  
General
1.    General
Description of Business
Century Aluminum is a producer of primary aluminum, which trades as a global commodity, and owns a 55% interest in a bauxite mining and alumina refinery joint venture. We are organized as a holding company, with our operating primary aluminum smelters and our bauxite mining and alumina refinery joint venture owned by separate subsidiaries.
Throughout this Form 10-Q, and unless expressly stated otherwise or as the context otherwise requires, "Century Aluminum", "Century", "the Company", "we", "us", "our" and "ours" refer to Century Aluminum Company and its consolidated subsidiaries.
Basis of Presentation
The accompanying unaudited interim consolidated financial statements of Century Aluminum Company should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2024. In management’s opinion, the unaudited interim consolidated financial statements reflect all adjustments, which are of a normal and recurring nature, that are necessary for a fair presentation of financial results for the interim periods presented. Operating results for the first six months of 2025 are not necessarily indicative of the results that may be expected for the year ending December 31, 2025.
Our consolidated financial statements include the consolidated results of the Jamalco joint venture ("Jamalco"), an unincorporated joint venture between Clarendon Alumina Production Limited ("CAP") and General Alumina Jamaica Limited ("GAJL"), an indirect, wholly-owned subsidiary of the Company through General Alumina Holdings Limited ("GAHL"). CAP's interest in the joint venture is reflected as noncontrolling interest on the accompanying Consolidated Balance Sheets. The acquisition of all the outstanding capital of GAHL 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 of fair value over the consideration paid to the seller presented as a bargain purchase gain of $245.9 million recognized within the Consolidated Statements of Operations for the six months ended June 30, 2024.
Recent Accounting Pronouncements
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.
v3.25.2
Related Party Transactions
 6 Months Ended
Jun. 30, 2025
Related Party Transactions [Abstract]  
Related Party Transactions
2.    Related Party Transactions
The significant related party transactions occurring during the three and six months ended June 30, 2025 and 2024 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 June 30, 2025, 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 13. Shareholders' Equity for a 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, alumina and other raw materials; tolling agreements; forward financial contracts and borrowing and other debt transactions.
Sales to Glencore
For the three months ended June 30, 2025 and 2024, we derived approximately 58.5% and 57.8% of our consolidated net sales from Glencore, respectively. For the six months ended June 30, 2025 and 2024, we derived approximately 59.1% and 60.8% of our consolidated net 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 primarily 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 three and six months ended June 30, 2025, the Company recognized $48.0 million and $126.4 million, respectively, of revenue related to alumina sales to Glencore. For the three and six months ended June 30, 2024, the Company recognized $50.3 million and $85.8 million, respectively, of revenue related to alumina sales to Glencore.
Purchases from Glencore
We purchase a portion of our alumina and certain other raw material requirements from Glencore. Alumina purchases from Glencore during the three and six months ended June 30, 2025 and 2024 were priced based on published alumina and aluminum indices as well as fixed prices.
Financial Contracts with Glencore
From time to time, we enter into certain financial contracts with Glencore. See Note 10. Derivatives regarding these forward financial sales contracts.
Summary
A summary of the aforementioned significant related party sales and purchases is as follows: 
 Three months ended
June 30,		Six months ended
June 30,
 2025202420252024
Net sales to Glencore367.6 324.2 746.3 $639.2 
Purchases from Glencore(1)
51.8 56.2 140.1 115.2 
(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. Under the Vlissingen Credit Facility Vlissingen may borrow from time to time up to $90.0 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 11. Debt for additional information. Borrowings under the Vlissingen Credit Facility are expected to be used for general corporate and working capital purposes of Century and its subsidiaries.
Carbon Credit Repurchase Agreement
In September 2023, our wholly owned subsidiary Nordural Grundartangi ehf ("Grundartangi"), entered into a structured repurchase arrangement with Glencore and 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 (the "Original Carbon Credit Agreement"). Pursuant to the terms of the Original Carbon Credit Agreement, Grundartangi would repurchase the same number of Carbon Credits at a price of €83.72 per Carbon Credit, for an aggregate amount of €32.7 million. The Original Carbon Credit Agreement was amended in December 2023, March 2024, August 2024 and December 2024, in each case to extend the repurchase window and increase the repurchase price (collectively, the "Amended Carbon Credit Agreement"). The Amended Carbon Credit Agreement (i) settled 19,300 Carbon Credits, (ii) extended the repurchase window from December 2024 to August 2025 for the remaining 370,700 Carbon Credits and (iii) revised the repurchase price to €69.16 per Carbon Credit, for an aggregate amount of €25.6 million.
In December 2023, Grundartangi also entered into a second structured repurchase agreement with Glencore pursuant to which it sold 40,000 Carbon Credits at a price of €69.30 per Carbon Credit and agreed to repurchase the same number of Carbon Credits at a price of €70.71 per Carbon Credit for an aggregate amount of €2.8 million (the "Second Carbon Credit Agreement"). In March 2024 and August 2024, the Second Carbon Credit Agreement was amended to (i) increase the number of Carbon Credits subject to the Second Carbon Agreement by 19,300 credits, (ii) extend the repurchase window from March 2024 to August 2024 with respect to all 59,300 Carbon Credits and (iii) revised the purchase price to €186.74 per Carbon Credit, for an aggregate amount of €11.1 million. On August 30, 2024 all 59,300 Carbon Credits subject to the Second Carbon Credit Agreement were settled in full.
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").
v3.25.2
Revenue
 6 Months Ended
Jun. 30, 2025
Revenue Recognition and Deferred Revenue [Abstract]  
Revenue
3.    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.
Contract liabilities are recorded when cash payments are received or due in advance of performance. Amounts recognized in Due to affiliates was $42.4 million and $41.2 million, as of June 30, 2025 and December 31, 2024, respectively.
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 three and six months ended June 30, 2025 and 2024.
Net SalesThree months ended June 30,Six months ended June 30,
2025202420252024
Aluminum$568.6 $454.9 $1,104.4 $904.3 
Alumina59.5 105.9 157.6 146.0 
Total$628.1 $560.8 $1,262.0 $1,050.3 
Our net sales are attributed to geographic area based on the location of the selling entity. Included in the consolidated financial statements are the following amounts related to geographic locations:
Three months ended June 30,Six months ended June 30,
 2025202420252024
Net sales: (1)
   
United States$391.8 $375.0 805.6 $675.0 
Iceland236.3 185.8 $456.4 375.3 
Total Net sales
$628.1 $560.8 $1,262.0 $1,050.3 
(1)Includes sales of primary aluminum, scrap aluminum and alumina, and purchased aluminum and alumina.
v3.25.2
Income Taxes
 6 Months Ended
Jun. 30, 2025
Income Tax Disclosure [Abstract]  
Income Taxes
4.    Income Taxes
For the three months ended June 30, 2025 and 2024, we recorded an income tax benefit of $1.3 million and an income tax expense of $0.5 million, respectively. For the six months ended June 30, 2025 and 2024, we recorded income tax expense of $0.3 million and $1.0 million, respectively. The change is primarily due to changes in pretax income amounts and jurisdictional mix on a year over year basis.
Our income tax expense or benefit for interim periods is determined using an estimate of our annual effective tax rate, adjusted for discrete items. The application of the accounting requirements for income taxes in interim periods, after consideration of our valuation allowance on domestic losses, causes a significant variation in the typical relationship between income tax expense/benefit and pretax accounting income/loss as reported on the Consolidated Statements of Operations.
As of June 30, 2025, all of Century's U.S. and certain foreign deferred tax assets, net of deferred tax liabilities, continue to be subject to a full valuation allowance.
Section 45X of the Inflation Reduction Act of 2022 ("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 October 24, 2024, the U.S. Department of the Treasury and the Internal Revenue Service issued final regulations on the production tax credit requirements under Internal Revenue Code Section 45X (the "IRA Regulations"). The IRA Regulations provide guidance on rules that taxpayers must satisfy to qualify for the IRA Section 45X tax credit. For the three months ended June 30, 2025 and 2024, the Company recognized a reduction of $21.9 million and $10.7 million in Cost of goods sold and a reduction of $0.5 million and $0.5 million in Selling, general and administrative expenses, respectively, within the Consolidated Statements of Operations. Comparatively, for the six months ended June 30, 2025 and 2024, the Company recognized a reduction of $41.8 million and $22.6 million in Cost of goods sold and a reduction of $1.3 million and $1.2 million in Selling, general and administrative expenses, respectively, within the Consolidated Statements of Operations.
v3.25.2
Earnings Per Share
 6 Months Ended
Jun. 30, 2025
Earnings Per Share [Abstract]  
Earnings Per Share
5.    Earnings Per Share
Basic earnings per share ("EPS") amounts are calculated by dividing earnings available to common stockholders by the weighted average number of common shares outstanding using the two-class method. Diluted EPS 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. Dilutive common equivalent shares are calculated using the more dilutive of either the if-converted or two-class methods.
The following table shows the basic and diluted earnings per share:
For the three months ended June 30,
20252024
Net Income (Loss)
Shares
(in millions)
$ Per ShareNet Income (Loss)
Shares
(in millions)
$ Per Share
Net (loss) income attributable to Century stockholders$(4.6)$(2.5)
Less: net income allocated to participating securities— — 
Basic EPS:
Net (loss) income allocated to common stockholders$(4.6)93.3 $(0.05)$(2.5)92.7 $(0.03)
Effect of Dilutive Securities(1):
Share-based compensation— — — — 
Convertible senior notes— — — — 
Diluted EPS:
Net (loss) income allocated to common stockholders$(4.6)93.3 $(0.05)$(2.5)92.7 $(0.03)
For the six months ended June 30,
2025
2024
Net Income (Loss)
Shares
(in millions)
Per ShareNet Income (Loss)
Shares
(in millions)
Per Share
Net (loss) income attributable to Century stockholders$25.1 $244.3 
Less: net income allocated to participating securities1.3 13.0 
Basic EPS:
Net (loss) income allocated to common stockholders$23.8 93.3 $0.26 $231.3 92.7 $2.50 
Effect of Dilutive Securities(1):
Share-based compensation— 1.3 (12.2)1.5 
Convertible senior notes— — 2.6 4.6 
Diluted EPS:
Net (loss) income allocated to common stockholders$23.8 94.6 $0.25 $221.7 98.8 $2.24 
Three months ended
June 30,		Six months ended
June 30,
Securities excluded from the calculation of diluted EPS (in millions)(1):
2025202420252024
Share-based compensation1.7 1.9 0.7 — 
Convertible preferred shares5.0 5.2 5.0 5.2 
Convertible notes4.6 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.
v3.25.2
Accumulated Other Comprehensive Loss ("AOCL")
 6 Months Ended
Jun. 30, 2025
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]  
Accumulated Other Comprehensive Loss ("AOCL")
6.    Accumulated Other Comprehensive Loss ("AOCL")
Components of AOCL:
June 30, 2025
December 31, 2024
Defined benefit plan liabilities
$(103.7)$(107.0)
Unrealized gain on financial instruments1.3 1.4 
Other comprehensive loss before income tax effect
(102.4)(105.6)
Income tax effect(1)
2.3 2.3 
Accumulated other comprehensive loss
$(100.1)$(103.3)
(1)The allocation of the income tax effect to the components of other comprehensive loss is as follows:
June 30, 2025
December 31, 2024
Defined benefit plan liabilities$2.6 $2.6 
Unrealized gain on financial instruments(0.3)(0.3)
The following table summarizes the changes in the accumulated balances for each component of AOCL:
Defined benefit plan and other postretirement liabilitiesUnrealized gain on financial instrumentsTotal, net of tax
Balance, March 31, 2025$(102.9)$1.3 $(101.6)
Other comprehensive loss before reclassifications— — — 
Net amount reclassified to net income (loss)1.6 (0.1)1.5 
Balance, June 30, 2025$(101.3)$1.2 $(100.1)
Balance, March 31, 2024$(101.0)$1.4 $(99.6)
Net amount reclassified to net income (loss)1.5 — 1.5 
Balance, June 30, 2024$(99.5)$1.4 $(98.1)
Balance, December 31, 2024$(104.6)$1.3 $(103.3)
Other comprehensive loss before reclassifications— — — 
Net amount reclassified to net income (loss)3.3 (0.1)3.2 
Balance, June 30, 2025$(101.3)$1.2 $(100.1)
Balance, December 31, 2023$(99.4)$1.5 $(97.9)
Other comprehensive loss before reclassifications$(3.4)— $(3.4)
Net amount reclassified to net income (loss)3.3 (0.1)3.2 
Balance, June 30, 2024$(99.5)$1.4 $(98.1)

Reclassifications out of AOCL were included in the Consolidated Statements of Operations as follows:
Three months ended
June 30,		Six months ended
June 30,
AOCL ComponentsLocation2025202420252024
Defined benefit plan and other postretirement liabilitiesCost of goods sold$1.5 $0.7 $2.3 $1.6 
Selling, general and administrative expenses0.1 0.1 0.3 0.3 
Other operating expense - net— 0.7 0.7 1.4 
Income tax effect— — — — 
Net of tax$1.6 $1.5 $3.3 $3.3 
Unrealized gain on financial instrumentsCost of goods sold$(0.1)$— $(0.1)$(0.1)
Income tax effect— — — — 
Net of tax$(0.1)$— $(0.1)$(0.1)
v3.25.2
Components of Net Periodic Benefit Cost
 6 Months Ended
Jun. 30, 2025
Retirement Benefits [Abstract]  
Components of Net Periodic Benefit Cost
7.    Components of Net Periodic Benefit Cost
Pension Benefits
Three months ended June 30,Six months ended
June 30,
2025202420252024
Service cost$0.6 $0.7 $1.3 $1.3 
Interest cost3.5 3.2 6.8 6.7 
Expected return on plan assets(4.0)(4.1)(7.9)(7.9)
Amortization of prior service benefit— — 0.1 0.1 
Amortization of net loss1.5 1.3 2.9 3.0 
Net periodic benefit cost$1.6 $1.1 $3.2 $3.2 
Other Postretirement Benefits
Three months ended June 30,Six months ended
June 30,
2025202420252024
Service cost$0.1 $0.1 $0.1 $0.1 
Interest cost0.9 0.9 1.9 1.9 
Amortization of prior service cost— (0.1)— (0.1)
Amortization of net loss0.1 0.3 0.3 0.3 
Net periodic benefit cost$1.1 $1.2 $2.3 $2.2 
v3.25.2
Inventories
 6 Months Ended
Jun. 30, 2025
Inventory, Net [Abstract]  
Inventories
8.    Inventories
Inventories consist of the following:
June 30, 2025December 31, 2024
Raw materials$178.5 $180.8 
Work-in-process50.6 52.1 
Finished goods57.7 74.6 
Operating and other supplies226.6 231.5 
Total inventories$513.4 $539.0 
Inventories are stated at the lower of cost or Net Realizable Value ("NRV") using the first-in, first-out or the weighted average cost method.
v3.25.2
Fair Value Measurements
 6 Months Ended
Jun. 30, 2025
Fair Value Disclosures [Abstract]  
Fair Value Measurements
9.    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 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 June 30, 2025
Level 1
Level 2
Level 3
Total
ASSETS:
Cash equivalents$2.8 $— $— $2.8 
Trust assets(1)
1.1 — — 1.1 
Derivative instruments— 4.6 — 4.6 
TOTAL$3.9 $4.6 $— $8.5 
LIABILITIES:
Derivative instruments$— $19.8 $— $19.8 
TOTAL$— $19.8 $— $19.8 

Recurring Fair Value Measurements
As of December 31, 2024
Level 1
Level 2
Level 3
Total
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 
(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 or inputs 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
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.
During the three and six months ended June 30, 2025 and 2024, there were no Level 3 assets and liabilities measured at fair value on a recurring basis.
v3.25.2
Derivatives
 6 Months Ended
Jun. 30, 2025
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Derivatives
10.    Derivatives
As of June 30, 2025, we had an open position of 37,400 tonnes related to LME forward financial sales contracts to fix the forward LME aluminum price. These contracts are expected to settle monthly through September 2026. We also had an open position of 37,400 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 June 30, 2025, we had 885 tonnes open fixed for floating swaps. These contracts are expected to settle monthly through November 2025.
We have entered into financial contracts to hedge a portion of our Jamalco fuel cost exposure ("HFO price swaps"). The volume of heavy fuel oil ("HFO") consumed at Jamalco is measured per barrel and as of June 30, 2025, we had an open position of 270,000 barrels. The HFO price swaps are expected to settle monthly through May 2026.
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 June 30, 2025, we had an open position of 690,648 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 June 30, 2025 and December 31, 2024, the Company had no recorded restricted cash as collateral related to open derivative contracts under the master arrangements with our counterparties.
The following tables set forth the Company's derivative assets and liabilities that were accounted for at fair value and not designated as cash flow hedges as of June 30, 2025 and December 31, 2024, respectively:
Asset Fair Value
June 30, 2025December 31, 2024
Commodity contracts(1)
$4.6 $4.5 
Liability Fair Value
June 30, 2025December 31, 2024
Commodity contracts(1)
$19.8 $4.4 
(1)Commodity contracts reflect our outstanding LME and MWP forward financial sales contracts, Indy Hub power price swaps, fixed for floating swaps, and HFO price swaps. At June 30, 2025, and December 31, 2024, there were no commodity contracts with Glencore.
The following table summarizes the net (loss) gain on forward and derivative contracts:
Three months ended
June 30,		Six months ended
June 30,
2025202420252024
Commodity contracts(1)
$(15.5)$(4.0)$(20.9)$3.5 
Foreign exchange contracts— — — (0.1)
   Total$(15.5)$(4.0)$(20.9)$3.4 
(1)For the three and six months ended June 30, 2025, there were no forward and derivative contracts with Glencore. For the three and six months ended June 30, 2024, $1.9 million of the net loss and $2.5 million of the net gain was with Glencore, respectively.
v3.25.2
Debt
 6 Months Ended
Jun. 30, 2025
Debt Disclosure [Abstract]  
Debt
11.    Debt
June 30, 2025December 31, 2024
Debt classified as current liabilities:
Hancock County industrial revenue bonds ("IRBs") due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%))(1)
$7.8 $7.8 
U.S. Revolving Credit Facility(2)
19.6 20.0 
Iceland Revolving Credit Facility(3)
— 34.0 
Grundartangi Casthouse Facility(4)
9.0 9.0 
Debt classified as non-current liabilities:
Grundartangi Casthouse Facility, net of financing fees of $1.0 million at June 30, 2025(4)
108.7 114.2 
Vlissingen Credit Facility(5)
10.0 10.0 
7.5% senior secured notes due April 1, 2028, net of financing fees of $1.6 million at June 30, 2025, interest payable semiannually
248.4 248.1 
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.0 million at June 30, 2025, interest payable semiannually
85.3 85.1 
Total$488.8 $528.2 
(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 June 30, 2025 was 2.05%.
(2)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at June 30, 2025 was 8.00%.
(3)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at June 30, 2025 was 7.82%.
(4)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at June 30, 2025 was 8.04%.
(5)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at June 30, 2025 was 7.98%.
7.5% Senior Secured Notes due 2028
In April 2021, we issued $250.0 million in aggregate principal amount of 7.5% senior secured notes due April 1, 2028 (the "2028 Notes"). We received proceeds of $245.2 million, after payment of certain financing fees and related expenses. The 2028 Notes bear interest semi-annually in arrears on April 1 and October 1 of each year, which began on October 1, 2021, at a rate of 7.5% per annum in cash. 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.
As of June 30, 2025, the total estimated fair value of the 2028 Notes was $254.1 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
In April 2021, we completed a private offering of $86.3 million aggregate principal amount of convertible senior notes due May 1, 2028 unless earlier converted, repurchased, or redeemed (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 Convertible Notes bear interest semi-annually in arrears on May 1 and November 1 of each year at a rate of 2.75% per annum in cash.
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. As of June 30, 2025, the conversion rate remains unchanged.
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.
As of June 30, 2025, the if-converted value of the Convertible Notes did not exceed the outstanding principal amount.
As of June 30, 2025, the total estimated fair value of the Convertible Notes was $103.3 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
We and certain of our direct and indirect domestic subsidiaries have a senior secured revolving credit facility with a syndicate of lenders (as amended from time to time, 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 in the aggregate, 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 June 30, 2025, there were $19.6 million of outstanding borrowings and $47.3 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:June 30, 2025
Credit facility maximum amount$250.0 
Borrowing availability208.6 
Outstanding letters of credit issued47.3 
Outstanding borrowings19.6 
Borrowing availability, net of outstanding letters of credit and borrowings141.8 
Iceland Revolving Credit Facility
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. On September 28, 2022, we further amended the Iceland revolving credit facility and increased the facility amount to $100.0 million in the 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 June 30, 2025, there were no 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:June 30, 2025
Credit facility maximum amount$100.0 
Borrowing availability100.0 
Outstanding letters of credit issued— 
Outstanding borrowings— 
Borrowing availability, net of borrowings100.0 
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 June 30, 2025, there were $117.7 million in outstanding borrowings under the Casthouse Facility.
Vlissingen Credit Facility
On December 9, 2022, Vlissingen entered into a $90.0 million 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 $90.0 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. As of June 30, 2025, there were $10.0 million in outstanding borrowings under the Vlissingen Credit Facility.
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 June 30, 2025, 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.
Covenant Compliance
As of June 30, 2025, we and our subsidiaries were in compliance with financial covenants or maintained availability above applicable covenant triggers.
v3.25.2
Commitments and Contingencies
 6 Months Ended
Jun. 30, 2025
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies
12.    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
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 June 30, 2025, $2.0 million was recorded in Accrued and other current liabilities and $1.8 million was recorded in Other liabilities.
PBGC Settlement
In 2013, we entered into a settlement agreement with the Pension Benefit Guaranty 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. In October 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 the next 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 June 30, 2025, we have made contributions of $7.2 million related to the Amended PBGC Settlement Agreement.
Power Commitments and Contingencies
Hawesville and Sebree
Hawesville and Sebree each has a power supply arrangement with Kenergy and Century Marketer, LLC ("Century Marketer"), Century's wholly-owned subsidiary that acts as a Midcontinent Independent System Operator ("MISO") market participant. Under these arrangements, Hawesville and Sebree get access to power at 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 and 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 contracts with Hawesville and Sebree both have 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 of aggregate power 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 88% 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 ratified on April 22, 2025, and is effective through December 31, 2030.
100% of Vlissingen's work force 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 38% 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 the 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 negotiated 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 June 30, 2025, the principal and accrued interest for the contingent obligation was $33.0 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 June 30, 2025, based on the curtailment of Hawesville's operations, 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.
v3.25.2
Shareholders’ Equity
 6 Months Ended
Jun. 30, 2025
Stockholders' Equity Note [Abstract]  
Shareholders’ Equity
13.    Shareholders' Equity
Common Stock
As of June 30, 2025 and December 31, 2024, we had 195,000,000 shares of common stock, $0.01 par value per share, authorized under our Restated Certificate of Incorporation, of which 100,525,642 shares were issued and 93,339,121 shares were outstanding at June 30, 2025, and 100,475,086 were issued and 93,288,565 shares were outstanding at December 31, 2024.
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 June 30, 2025 and December 31, 2024, we had 5,000,000 shares of preferred stock, $0.01 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, liquidating 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. At June 30, 2025 and December 31, 2024, 49,514 and 49,715 shares of Series A Convertible Preferred Stock were outstanding, respectively. Glencore holds all of the issued and outstanding Series A Convertible Preferred Stock.
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 stock for each share of preferred stock. Our Series A Convertible Preferred Stock has a par value of $0.01 per share.
Stock Repurchase Program
In 2011, our Board of Directors authorized a $60.0 million common 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 convertible 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 June 30, 2025 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 June 30, 2025.
v3.25.2
Business Segments
 6 Months Ended
Jun. 30, 2025
Segment Reporting [Abstract]  
Business Segments
14.    Business Segments
The Company is a producer of alumina and primary aluminum. The Company has organized itself, including management personnel and systems, financial processes, operational execution, governance and risk oversight, regulatory compliance, and
every other aspect of the Company’s operations, to assess and manage the business on a holistic basis, from mine to metal, which tracks the upstream manufacturing process for aluminum. To better reflect this operational and organizational approach, and to further enhance the reporting of its financial and operating results, beginning with the quarter ended March 31, 2025, the Company’s Chief Executive Officer and Chief Operating Decision Maker ("CODM") regularly receives and reviews financial information at the consolidated level to evaluate business performance and make operating decisions. The CODM uses the U.S. GAAP measure of consolidated Net Income to evaluate the Company’s financial performance and allocate resources.
Given the change described above, the Company has determined that neither its three smelters nor Jamalco’s mining and refining operations meet the definition of operating segments. As a result, the Company has determined that the Company has only one operating and only one reportable segment, and it is managed on a consolidated basis. In accordance with ASC 280-10-50-34, the corresponding information for earlier periods is recast in the tables below to conform with the updated presentation.
The CODM uses the U.S. GAAP measurement of consolidated Net income to develop forecasting, evaluate overall profitability performance and to make key operating decisions, such as the allocation of budget between sales, cost of good sold and selling, general and administrative expenses.
Segment assets are reported on our Consolidated Balance Sheets as Total assets. Our Consolidated Statements of Cash Flows presents Depreciation, depletion and amortization expense and includes the measure of Capital expenditures as Purchase of property, plant and equipment.
The following table presents information about the Company's single segment for the three and six months ended June 30, 2025 and 2024.
Three months ended
June 30,		Six months ended
June 30,
2025202420252024
Net sales$628.1 $560.8 $1,262.0 $1,050.3 
Segment Cost of goods sold(1),(2)
(593.2)(532.0)(1,165.6)(1,001.5)
IRA Credit(1),(3)
21.9 10.7 41.8 22.6 
Lower of cost or NRV inventory adjustment(1),(4)
1.2 1.7 1.9 7.3 
Property and equipment expense(1),(5)
(21.8)(20.8)(43.3)(41.8)
Selling, general and administrative expenses(14.0)(12.3)(26.5)(26.4)
Other operating expenses - net(1.5)(1.7)(3.5)(2.2)
Interest expense - nonaffiliates(9.8)(8.9)(19.8)(16.2)
Interest expense - affiliates(1.9)(1.4)(3.7)(3.3)
Interest income1.9 0.6 3.7 1.3 
Net (loss) gain on forward and derivative contracts - nonaffiliates(15.6)(2.1)(21.0)0.9 
Net (loss) gain on forward and derivative contracts - affiliates— (1.9)— 2.5 
Bargain purchase gain— — — 245.9 
Other (loss) income - net(5.7)1.1 (9.1)(0.4)
Income tax benefit (expense)1.3 (0.5)(0.3)(1.0)
Net (loss) income$(9.1)$(6.7)$16.6 $238.0 
(1)Indicates a component of Cost of goods sold.
(2)Includes raw materials, labor, energy, freight costs, FIFO inventory adjustments and other direct cost of goods sold.
(3)Advanced production credit related to Section 45X of the IRA.
(4)Includes inventory revaluation to lower of cost or net realizable value and changes in inventory reserve.
(5)Represents the depreciation expenses and expenses related to leased assets that are directly related to the cost of goods sold.
v3.25.2
Variable Interest Entity
 6 Months Ended
Jun. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Variable Interest Entity
15.    Variable Interest Entity
The Company consolidates Jamalco, a bauxite mining and alumina refinery in Jamaica, under the variable interest entity ("VIE") model. 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.
The Company owns a 55% ownership interest in Jamalco through its wholly-owned subsidiary, GAJL, which serves as the managing partner. The Company is responsible for funding 55% of Jamalco's operating costs and capital requirements and is not obligated to provide additional financial support beyond its equity interest. Upon acquisition, the Company made an immediate equity contribution to Jamalco and has provided subsequent financing of costs for Jamalco to perform its activities in the ordinary course of business.
The Company obtains direct ownership of our 55% share of Jamalco’s outputs and purchases the remaining 45% of the output from the Government of Jamaica. Through direct ownership and purchase, 100% of Jamalco’s output is either retained and utilized in the Company’s business operations or sold by the Company. The Company’s consolidated statement of cash flows reflects 100% of cash flows related to the Jamalco operations. The Company receives cash proceeds from the Government of Jamaica for its 45% interest of the Jamalco operating costs and capital requirements.
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 June 30, 2025 and December 31, 2024.
June 30, 2025
December 31, 2024
ASSETS
Cash and cash equivalents33.0 17.4 
Accounts receivable - net0.6 1.1 
Non-trade receivables— 13.1 
Due from affiliates— 75.1 
Inventories85.5 109.8 
Prepaid and other current assets5.3 2.0 
Total current assets124.4 218.5 
Property, plant and equipment - net54.5 232.1 
Other assets10.9 23.1 
TOTAL189.8 473.7 
LIABILITIES
LIABILITIES:
Accounts payable, trade43.4 39.1 
Accrued compensation and benefits6.1 8.5 
Due to affiliates14.3 49.6 
Accrued and other current liabilities2.7 7.2 
Total current liabilities66.5 104.4 
Accrued benefits costs - less current portion— 17.7 
Other liabilities61.9 66.7 
Asset retirement obligations - less current portion10.9 35.0 
Total noncurrent liabilities72.8 119.4 
TOTAL
139.3 223.8 
v3.25.2
Subsequent Events
 6 Months Ended
Jun. 30, 2025
Subsequent Events [Abstract]  
Subsequent Events Subsequent Events
Refinancing Transactions
On July 22, 2025, we completed the issuance of $400.0 million aggregate principal amount of 6.875% Senior Secured Notes due August 2032 (the "2032 Notes"). We received net proceeds of $395 million after payment of certain financing fees and related expenses. The net proceeds have been, or will be, applied as described below. The 2032 Notes bear interest semi-annually in arrears on February 1 and August 1 of each year, beginning on February 1, 2026, at a rate of 6.875% per annum payable in cash. The 2032 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. The net proceeds from the 2032 Notes issuance were used to redeem the 2028 Notes and will be used to repay borrowings under the Company's credit facilities and to pay fees and expenses relating to these transactions.
On July 22, 2025, we determined that all conditions precedent to the redemption (the “Redemption”) of our 2028 Notes pursuant to its Conditional Notice of Full Redemption issued on July 21, 2025 had been satisfied. Accordingly, the 2028 Notes were redeemed on August 5, 2025 at an aggregate redemption price of $261.1 million, consisting of 101.875% of the principal due and payable on the 2028 Notes plus accrued and unpaid interest to but excluding the August 5, 2025 redemption date. In connection with the Redemption, effective July 22, 2025, the Company satisfied and discharged all its obligations under and in accordance with the terms of the indenture governing the 2028 Notes.
On August 1, 2025, we repaid the $10 million in outstanding borrowings under the Vlissingen Credit Facility.
Fifth Amendment to Second Amended and Restated Loan and Security Agreement
On July 22, 2025, we amended the U.S. revolving credit facility to, among other items, extend the maturity date of the Existing Credit Facility to July 22, 2030 and revise the calculation of Term SOFR Adjustment (as defined in the Existing Credit Facility) to 0.10% per annum for all interest periods.
v3.25.2
Insider Trading Arrangements
 3 Months Ended
Jun. 30, 2025
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
v3.25.2
General (Policies)
 6 Months Ended
Jun. 30, 2025
Accounting Policies [Abstract]  
Basis of Presentation
Basis of Presentation
The accompanying unaudited interim consolidated financial statements of Century Aluminum Company should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2024. In management’s opinion, the unaudited interim consolidated financial statements reflect all adjustments, which are of a normal and recurring nature, that are necessary for a fair presentation of financial results for the interim periods presented. Operating results for the first six months of 2025 are not necessarily indicative of the results that may be expected for the year ending December 31, 2025.
Recent Accounting Pronouncements
Recent Accounting Pronouncements
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.
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.
v3.25.2
Related Party Transactions (Tables)
 6 Months Ended
Jun. 30, 2025
Related Party Transactions [Abstract]  
Schedule of related party transactions
A summary of the aforementioned significant related party sales and purchases is as follows: 
 Three months ended
June 30,		Six months ended
June 30,
 2025202420252024
Net sales to Glencore367.6 324.2 746.3 $639.2 
Purchases from Glencore(1)
51.8 56.2 140.1 115.2 
(1)Includes settlements of financial contract positions.
v3.25.2
Revenue (Tables)
 6 Months Ended
Jun. 30, 2025
Revenue Recognition and Deferred Revenue [Abstract]  
Schedule of disaggregation of revenue
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 three and six months ended June 30, 2025 and 2024.
Net SalesThree months ended June 30,Six months ended June 30,
2025202420252024
Aluminum$568.6 $454.9 $1,104.4 $904.3 
Alumina59.5 105.9 157.6 146.0 
Total$628.1 $560.8 $1,262.0 $1,050.3 
Schedule of revenue by geographic area
Our net sales are attributed to geographic area based on the location of the selling entity. Included in the consolidated financial statements are the following amounts related to geographic locations:
Three months ended June 30,Six months ended June 30,
 2025202420252024
Net sales: (1)
   
United States$391.8 $375.0 805.6 $675.0 
Iceland236.3 185.8 $456.4 375.3 
Total Net sales
$628.1 $560.8 $1,262.0 $1,050.3 
(1)Includes sales of primary aluminum, scrap aluminum and alumina, and purchased aluminum and alumina.
v3.25.2
Earnings Per Share (Tables)
 6 Months Ended
Jun. 30, 2025
Earnings Per Share [Abstract]  
Schedule of basic and diluted earnings per share and securities excluded from the calculation of diluted EPS
The following table shows the basic and diluted earnings per share:
For the three months ended June 30,
20252024
Net Income (Loss)
Shares
(in millions)
$ Per ShareNet Income (Loss)
Shares
(in millions)
$ Per Share
Net (loss) income attributable to Century stockholders$(4.6)$(2.5)
Less: net income allocated to participating securities— — 
Basic EPS:
Net (loss) income allocated to common stockholders$(4.6)93.3 $(0.05)$(2.5)92.7 $(0.03)
Effect of Dilutive Securities(1):
Share-based compensation— — — — 
Convertible senior notes— — — — 
Diluted EPS:
Net (loss) income allocated to common stockholders$(4.6)93.3 $(0.05)$(2.5)92.7 $(0.03)
For the six months ended June 30,
2025
2024
Net Income (Loss)
Shares
(in millions)
Per ShareNet Income (Loss)
Shares
(in millions)
Per Share
Net (loss) income attributable to Century stockholders$25.1 $244.3 
Less: net income allocated to participating securities1.3 13.0 
Basic EPS:
Net (loss) income allocated to common stockholders$23.8 93.3 $0.26 $231.3 92.7 $2.50 
Effect of Dilutive Securities(1):
Share-based compensation— 1.3 (12.2)1.5 
Convertible senior notes— — 2.6 4.6 
Diluted EPS:
Net (loss) income allocated to common stockholders$23.8 94.6 $0.25 $221.7 98.8 $2.24 
Three months ended
June 30,		Six months ended
June 30,
Securities excluded from the calculation of diluted EPS (in millions)(1):
2025202420252024
Share-based compensation1.7 1.9 0.7 — 
Convertible preferred shares5.0 5.2 5.0 5.2 
Convertible notes4.6 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.
v3.25.2
Accumulated Other Comprehensive Loss ("AOCL") (Tables)
 6 Months Ended
Jun. 30, 2025
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]  
Schedule of accumulated balances for each component of AOCI
Components of AOCL:
June 30, 2025
December 31, 2024
Defined benefit plan liabilities
$(103.7)$(107.0)
Unrealized gain on financial instruments1.3 1.4 
Other comprehensive loss before income tax effect
(102.4)(105.6)
Income tax effect(1)
2.3 2.3 
Accumulated other comprehensive loss
$(100.1)$(103.3)
(1)The allocation of the income tax effect to the components of other comprehensive loss is as follows:
June 30, 2025
December 31, 2024
Defined benefit plan liabilities$2.6 $2.6 
Unrealized gain on financial instruments(0.3)(0.3)
The following table summarizes the changes in the accumulated balances for each component of AOCL:
Defined benefit plan and other postretirement liabilitiesUnrealized gain on financial instrumentsTotal, net of tax
Balance, March 31, 2025$(102.9)$1.3 $(101.6)
Other comprehensive loss before reclassifications— — — 
Net amount reclassified to net income (loss)1.6 (0.1)1.5 
Balance, June 30, 2025$(101.3)$1.2 $(100.1)
Balance, March 31, 2024$(101.0)$1.4 $(99.6)
Net amount reclassified to net income (loss)1.5 — 1.5 
Balance, June 30, 2024$(99.5)$1.4 $(98.1)
Balance, December 31, 2024$(104.6)$1.3 $(103.3)
Other comprehensive loss before reclassifications— — — 
Net amount reclassified to net income (loss)3.3 (0.1)3.2 
Balance, June 30, 2025$(101.3)$1.2 $(100.1)
Balance, December 31, 2023$(99.4)$1.5 $(97.9)
Other comprehensive loss before reclassifications$(3.4)— $(3.4)
Net amount reclassified to net income (loss)3.3 (0.1)3.2 
Balance, June 30, 2024$(99.5)$1.4 $(98.1)
Schedule of reclassification out of AOCI
Reclassifications out of AOCL were included in the Consolidated Statements of Operations as follows:
Three months ended
June 30,		Six months ended
June 30,
AOCL ComponentsLocation2025202420252024
Defined benefit plan and other postretirement liabilitiesCost of goods sold$1.5 $0.7 $2.3 $1.6 
Selling, general and administrative expenses0.1 0.1 0.3 0.3 
Other operating expense - net— 0.7 0.7 1.4 
Income tax effect— — — — 
Net of tax$1.6 $1.5 $3.3 $3.3 
Unrealized gain on financial instrumentsCost of goods sold$(0.1)$— $(0.1)$(0.1)
Income tax effect— — — — 
Net of tax$(0.1)$— $(0.1)$(0.1)
v3.25.2
Components of Net Periodic Benefit Cost (Tables)
 6 Months Ended
Jun. 30, 2025
Retirement Benefits [Abstract]  
Schedule of net periodic benefit cost
Pension Benefits
Three months ended June 30,Six months ended
June 30,
2025202420252024
Service cost$0.6 $0.7 $1.3 $1.3 
Interest cost3.5 3.2 6.8 6.7 
Expected return on plan assets(4.0)(4.1)(7.9)(7.9)
Amortization of prior service benefit— — 0.1 0.1 
Amortization of net loss1.5 1.3 2.9 3.0 
Net periodic benefit cost$1.6 $1.1 $3.2 $3.2 
Other Postretirement Benefits
Three months ended June 30,Six months ended
June 30,
2025202420252024
Service cost$0.1 $0.1 $0.1 $0.1 
Interest cost0.9 0.9 1.9 1.9 
Amortization of prior service cost— (0.1)— (0.1)
Amortization of net loss0.1 0.3 0.3 0.3 
Net periodic benefit cost$1.1 $1.2 $2.3 $2.2 
v3.25.2
Inventories (Tables)
 6 Months Ended
Jun. 30, 2025
Inventory, Net [Abstract]  
Schedule of inventories
Inventories consist of the following:
June 30, 2025December 31, 2024
Raw materials$178.5 $180.8 
Work-in-process50.6 52.1 
Finished goods57.7 74.6 
Operating and other supplies226.6 231.5 
Total inventories$513.4 $539.0 
v3.25.2
Fair Value Measurements (Tables)
 6 Months Ended
Jun. 30, 2025
Fair Value Disclosures [Abstract]  
Schedule of financial assets and liabilities at fair value on a recurring basis
Recurring Fair Value Measurements
As of June 30, 2025
Level 1
Level 2
Level 3
Total
ASSETS:
Cash equivalents$2.8 $— $— $2.8 
Trust assets(1)
1.1 — — 1.1 
Derivative instruments— 4.6 — 4.6 
TOTAL$3.9 $4.6 $— $8.5 
LIABILITIES:
Derivative instruments$— $19.8 $— $19.8 
TOTAL$— $19.8 $— $19.8 

Recurring Fair Value Measurements
As of December 31, 2024
Level 1
Level 2
Level 3
Total
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 
(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 or inputs 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
Heavy Fuel Oil ("HFO") price swapsDiscounted cash flowsQuoted HFO forward market
v3.25.2
Derivatives (Tables)
 6 Months Ended
Jun. 30, 2025
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Schedule of derivatives not designated as hedging instruments
The following tables set forth the Company's derivative assets and liabilities that were accounted for at fair value and not designated as cash flow hedges as of June 30, 2025 and December 31, 2024, respectively:
Asset Fair Value
June 30, 2025December 31, 2024
Commodity contracts(1)
$4.6 $4.5 
Liability Fair Value
June 30, 2025December 31, 2024
Commodity contracts(1)
$19.8 $4.4 
(1)Commodity contracts reflect our outstanding LME and MWP forward financial sales contracts, Indy Hub power price swaps, fixed for floating swaps, and HFO price swaps. At June 30, 2025, and December 31, 2024, there were no commodity contracts with Glencore.
Schedule of derivative instruments
The following table summarizes the net (loss) gain on forward and derivative contracts:
Three months ended
June 30,		Six months ended
June 30,
2025202420252024
Commodity contracts(1)
$(15.5)$(4.0)$(20.9)$3.5 
Foreign exchange contracts— — — (0.1)
   Total$(15.5)$(4.0)$(20.9)$3.4 
(1)For the three and six months ended June 30, 2025, there were no forward and derivative contracts with Glencore. For the three and six months ended June 30, 2024, $1.9 million of the net loss and $2.5 million of the net gain was with Glencore, respectively.
v3.25.2
Debt (Tables)
 6 Months Ended
Jun. 30, 2025
Debt Disclosure [Abstract]  
Schedule of debt
June 30, 2025December 31, 2024
Debt classified as current liabilities:
Hancock County industrial revenue bonds ("IRBs") due April 1, 2028, interest payable quarterly (variable interest rates (not to exceed 12%))(1)
$7.8 $7.8 
U.S. Revolving Credit Facility(2)
19.6 20.0 
Iceland Revolving Credit Facility(3)
— 34.0 
Grundartangi Casthouse Facility(4)
9.0 9.0 
Debt classified as non-current liabilities:
Grundartangi Casthouse Facility, net of financing fees of $1.0 million at June 30, 2025(4)
108.7 114.2 
Vlissingen Credit Facility(5)
10.0 10.0 
7.5% senior secured notes due April 1, 2028, net of financing fees of $1.6 million at June 30, 2025, interest payable semiannually
248.4 248.1 
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.0 million at June 30, 2025, interest payable semiannually
85.3 85.1 
Total$488.8 $528.2 
(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 June 30, 2025 was 2.05%.
(2)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at June 30, 2025 was 8.00%.
(3)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at June 30, 2025 was 7.82%.
(4)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at June 30, 2025 was 8.04%.
(5)We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at June 30, 2025 was 7.98%.
Schedule of line of credit facilities
Status of our U.S. revolving credit facility:June 30, 2025
Credit facility maximum amount$250.0 
Borrowing availability208.6 
Outstanding letters of credit issued47.3 
Outstanding borrowings19.6 
Borrowing availability, net of outstanding letters of credit and borrowings141.8 
Status of our Iceland revolving credit facility:June 30, 2025
Credit facility maximum amount$100.0 
Borrowing availability100.0 
Outstanding letters of credit issued— 
Outstanding borrowings— 
Borrowing availability, net of borrowings100.0 
v3.25.2
Business Segments (Tables)
 6 Months Ended
Jun. 30, 2025
Segment Reporting [Abstract]  
Schedule of segment information
The following table presents information about the Company's single segment for the three and six months ended June 30, 2025 and 2024.
Three months ended
June 30,		Six months ended
June 30,
2025202420252024
Net sales$628.1 $560.8 $1,262.0 $1,050.3 
Segment Cost of goods sold(1),(2)
(593.2)(532.0)(1,165.6)(1,001.5)
IRA Credit(1),(3)
21.9 10.7 41.8 22.6 
Lower of cost or NRV inventory adjustment(1),(4)
1.2 1.7 1.9 7.3 
Property and equipment expense(1),(5)
(21.8)(20.8)(43.3)(41.8)
Selling, general and administrative expenses(14.0)(12.3)(26.5)(26.4)
Other operating expenses - net(1.5)(1.7)(3.5)(2.2)
Interest expense - nonaffiliates(9.8)(8.9)(19.8)(16.2)
Interest expense - affiliates(1.9)(1.4)(3.7)(3.3)
Interest income1.9 0.6 3.7 1.3 
Net (loss) gain on forward and derivative contracts - nonaffiliates(15.6)(2.1)(21.0)0.9 
Net (loss) gain on forward and derivative contracts - affiliates— (1.9)— 2.5 
Bargain purchase gain— — — 245.9 
Other (loss) income - net(5.7)1.1 (9.1)(0.4)
Income tax benefit (expense)1.3 (0.5)(0.3)(1.0)
Net (loss) income$(9.1)$(6.7)$16.6 $238.0 
(1)Indicates a component of Cost of goods sold.
(2)Includes raw materials, labor, energy, freight costs, FIFO inventory adjustments and other direct cost of goods sold.
(3)Advanced production credit related to Section 45X of the IRA.
(4)Includes inventory revaluation to lower of cost or net realizable value and changes in inventory reserve.
(5)Represents the depreciation expenses and expenses related to leased assets that are directly related to the cost of goods sold.
v3.25.2
Variable Interest Entity (Tables)
 6 Months Ended
Jun. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Schedule of consolidated VIE's assets and liabilities
The table below shows the carrying amounts and classification of the consolidated VIE's assets and liabilities included in the Consolidated Balance Sheets as of June 30, 2025 and December 31, 2024.
June 30, 2025
December 31, 2024
ASSETS
Cash and cash equivalents33.0 17.4 
Accounts receivable - net0.6 1.1 
Non-trade receivables— 13.1 
Due from affiliates— 75.1 
Inventories85.5 109.8 
Prepaid and other current assets5.3 2.0 
Total current assets124.4 218.5 
Property, plant and equipment - net54.5 232.1 
Other assets10.9 23.1 
TOTAL189.8 473.7 
LIABILITIES
LIABILITIES:
Accounts payable, trade43.4 39.1 
Accrued compensation and benefits6.1 8.5 
Due to affiliates14.3 49.6 
Accrued and other current liabilities2.7 7.2 
Total current liabilities66.5 104.4 
Accrued benefits costs - less current portion— 17.7 
Other liabilities61.9 66.7 
Asset retirement obligations - less current portion10.9 35.0 
Total noncurrent liabilities72.8 119.4 
TOTAL
139.3 223.8 
v3.25.2
General (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Segment Reporting Information [Line Items]        
Bargain purchase gain $ 0.0 $ 0.0 $ 0.0 $ 245.9
Bauxite Mining and Alumina Refinery Joint Venture        
Segment Reporting Information [Line Items]        
Noncontrolling interest, ownership percentage by parent 55.00%   55.00%  
General Alumina Holdings Limited        
Segment Reporting Information [Line Items]        
Bargain purchase gain       $ 245.9
v3.25.2
Related Party Transactions - Narrative (Details)
€ in Millions, $ in Millions
 1 Months Ended 3 Months Ended 6 Months Ended
Oct. 01, 2024
USD ($)
Dec. 31, 2024
EUR (€)
carbon_credit
€ / carbonCredit
Aug. 31, 2024
EUR (€)
carbon_credit
€ / carbonCredit
Dec. 31, 2023
EUR (€)
carbon_credit
€ / carbonCredit
Sep. 30, 2023
EUR (€)
carbon_credit
€ / carbonCredit
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Aug. 30, 2024
carbon_credit
Related Party Transaction [Line Items]                    
Net sales | $           $ 628.1 $ 560.8 $ 1,262.0 $ 1,050.3  
Vlissingen Credit Facility | Affiliated Entity | Vlissingen                    
Related Party Transaction [Line Items]                    
Term extension 2 years                  
Credit facility maximum amount | $ $ 90.0                  
Stated interest rate, percentage 8.75%                  
Debt instrument, basis spread on variable rate 3.687%                  
Vlissingen Credit Facility | Affiliated Entity | Vlissingen | Maximum                    
Related Party Transaction [Line Items]                    
Variable interest rate 9.00%                  
Vlissingen Credit Facility | Affiliated Entity | Vlissingen | Minimum                    
Related Party Transaction [Line Items]                    
Variable interest rate 7.00%                  
Carbon Credit Sale | Affiliated Entity | Grundartangi                    
Related Party Transaction [Line Items]                    
Carbon credit sold in transaction   370,700     390,000          
Sale price (Euro per carbon credit) | € / carbonCredit         82.18          
Aggregate amount | €         € 32.1          
Carbon Credit Repurchase | Affiliated Entity | Grundartangi                    
Related Party Transaction [Line Items]                    
Sale price (Euro per carbon credit) | € / carbonCredit   69.16     83.72          
Aggregate amount | €   € 25.6     € 32.7          
Repurchase Agreement, Carbon Credits Settled | Affiliated Entity | Grundartangi                    
Related Party Transaction [Line Items]                    
Carbon credit sold in transaction   19,300                
Second Repurchase Agreement | Affiliated Entity | Grundartangi                    
Related Party Transaction [Line Items]                    
Carbon credit sold in transaction     59,300              
Sale price (Euro per carbon credit) | € / carbonCredit     186.74              
Aggregate amount | €     € 11.1              
Carbon Credit Sale | Affiliated Entity | Grundartangi                    
Related Party Transaction [Line Items]                    
Carbon credit sold in transaction       40,000            
Sale price (Euro per carbon credit) | € / carbonCredit       69.30            
Carbon Credit Repurchase | Affiliated Entity | Grundartangi                    
Related Party Transaction [Line Items]                    
Sale price (Euro per carbon credit) | € / carbonCredit       70.71            
Aggregate amount | €       € 2.8            
Carbon Credit Increase | Affiliated Entity | Grundartangi                    
Related Party Transaction [Line Items]                    
Carbon credit sold in transaction     19,300              
Carbon Credit Settled | Affiliated Entity | Grundartangi                    
Related Party Transaction [Line Items]                    
Carbon credit sold in transaction                   59,300
Glencore | Supply Commitment                    
Related Party Transaction [Line Items]                    
Net sales | $           $ 48.0 $ 50.3 $ 126.4 $ 85.8  
Glencore | Consolidated sales | Customer concentration risk                    
Related Party Transaction [Line Items]                    
Major customer, percentage of revenue, net (percent)           58.50% 57.80% 59.10% 60.80%  
Century Aluminum | Glencore                    
Related Party Transaction [Line Items]                    
Ownership percentage by noncontrolling owners           42.90%   42.90%    
Economic ownership percentage by related party           45.80%   45.80%    
v3.25.2
Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Related Party Transaction [Line Items]        
Net sales $ 628.1 $ 560.8 $ 1,262.0 $ 1,050.3
Related Party        
Related Party Transaction [Line Items]        
Net sales 367.6 324.2 746.3 639.2
Related Party | Glencore        
Related Party Transaction [Line Items]        
Net sales 367.6 324.2 746.3 639.2
Purchases from Glencore $ 51.8 $ 56.2 $ 140.1 $ 115.2
v3.25.2
Revenue - Narrative (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Revenue from Contract with Customer [Abstract]    
Contract liabilities $ 42.4 $ 41.2
v3.25.2
Revenue - Disaggregation of Revenue by Product Category (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Disaggregation of Revenue [Line Items]        
Net sales $ 628.1 $ 560.8 $ 1,262.0 $ 1,050.3
Aluminum        
Disaggregation of Revenue [Line Items]        
Net sales 568.6 454.9 1,104.4 904.3
Alumina        
Disaggregation of Revenue [Line Items]        
Net sales $ 59.5 $ 105.9 $ 157.6 $ 146.0
v3.25.2
Revenue - Schedule of Revenue by Geographic Area (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Disaggregation of Revenue [Line Items]        
Net sales $ 628.1 $ 560.8 $ 1,262.0 $ 1,050.3
United States        
Disaggregation of Revenue [Line Items]        
Net sales 391.8 375.0 805.6 675.0
Iceland        
Disaggregation of Revenue [Line Items]        
Net sales $ 236.3 $ 185.8 $ 456.4 $ 375.3
v3.25.2
Income Taxes (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]        
Income tax expense (benefit) $ (1.3) $ 0.5 $ 0.3 $ 1.0
Reduction in cost of goods sold (591.9) (540.4) (1,165.2) [1] (1,013.4) [1]
Reduction in selling, general and administrative expenses (14.0) (12.3) (26.5) (26.4)
Inflation Reduction Act        
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]        
Reduction in cost of goods sold 21.9 10.7 41.8 22.6
Reduction in selling, general and administrative expenses $ 0.5 $ 0.5 $ 1.3 $ 1.2
[1]
(1) Purchases from related party were $51.8 million and $56.2 million for the three months ended June 30, 2025 and 2024, respectively. Purchases from related parties were $140.1 million and $115.2 million for the six months ended June 30, 2025 and 2024, respectively.
v3.25.2
Earnings Per Share - Schedule of EPS (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Earnings Per Share [Abstract]        
Net (loss) income attributable to Century stockholders $ (4.6) $ (2.5) $ 25.1 $ 244.3
Less: net income allocated to participating securities 0.0 0.0 1.3 13.0
Basic EPS:        
Net (loss) income allocated to common stockholders $ (4.6) $ (2.5) $ 23.8 $ 231.3
Net (loss) income allocated to common stockholders (in shares) 93.3 92.7 93.3 92.7
Net (loss) income allocated to common stockholders (in dollars per share) $ (0.05) $ (0.03) $ 0.26 $ 2.50
Effect of Dilutive Securities        
Share-based compensation $ 0.0 $ 0.0 $ 0.0 $ (12.2)
Share-based compensation (in shares) 0.0 0.0 1.3 1.5
Convertible senior notes $ 0.0 $ 0.0 $ 0.0 $ 2.6
Convertible senior notes (in shares) 0.0 0.0 0.0 4.6
Diluted EPS:        
Net (loss) income allocated to common stockholders $ (4.6) $ (2.5) $ 23.8 $ 221.7
Net (loss) income allocated to common stockholders (in shares) 93.3 92.7 94.6 98.8
Net (loss) income allocated to common stockholders (in dollars per share) $ (0.05) $ (0.03) $ 0.25 $ 2.24
v3.25.2
Earnings Per Share - Securities Excluded (Details) - shares
shares in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Share-based compensation        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Securities excluded from calculation of diluted EPS (in shares) 1.7 1.9 0.7 0.0
Convertible preferred shares        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Securities excluded from calculation of diluted EPS (in shares) 5.0 5.2 5.0 5.2
Convertible notes        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Securities excluded from calculation of diluted EPS (in shares) 4.6 4.6 4.6 0.0
v3.25.2
Accumulated Other Comprehensive Loss ("AOCL") - Components of AOCL (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]          
Other comprehensive loss before income tax effect $ (102.4)   $ (102.4)   $ (105.6)
Defined benefit plan liabilities 2.3   2.3   2.3
Accumulated other comprehensive loss (100.1)   (100.1)   (103.3)
AOCI Attributable to Parent, Net of Tax [Roll Forward]          
Beginning balance 690.7 $ 587.1 662.7 $ 344.1  
Other comprehensive loss before reclassifications 0.0   0.0 (3.4)  
Net amount reclassified to net income (loss) 1.5 1.5 3.2 3.2  
Ending balance 684.3 582.9 684.3 582.9  
Defined benefit plan liabilities          
Accumulated Other Comprehensive Income (Loss) [Line Items]          
Other comprehensive loss before income tax effect (103.7)   (103.7)   (107.0)
Defined benefit plan liabilities 2.6   2.6   2.6
AOCI Attributable to Parent, Net of Tax [Roll Forward]          
Beginning balance (102.9) (101.0) (104.6) (99.4)  
Other comprehensive loss before reclassifications 0.0   0.0 (3.4)  
Net amount reclassified to net income (loss) 1.6 1.5 3.3 3.3  
Ending balance (101.3) (99.5) (101.3) (99.5)  
Unrealized gain on financial instruments          
Accumulated Other Comprehensive Income (Loss) [Line Items]          
Other comprehensive loss before income tax effect 1.3   1.3   1.4
Defined benefit plan liabilities (0.3)   (0.3)   $ (0.3)
AOCI Attributable to Parent, Net of Tax [Roll Forward]          
Beginning balance 1.3 1.4 1.3 1.5  
Other comprehensive loss before reclassifications 0.0   0.0 0.0  
Net amount reclassified to net income (loss) (0.1) 0.0 (0.1) (0.1)  
Ending balance 1.2 1.4 1.2 1.4  
Accumulated other comprehensive loss          
AOCI Attributable to Parent, Net of Tax [Roll Forward]          
Beginning balance (101.6) (99.6) (103.3) (97.9)  
Ending balance $ (100.1) $ (98.1) $ (100.1) $ (98.1)  
v3.25.2
Accumulated Other Comprehensive Loss ("AOCL") - Reclassifications out of AOCL (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Cost of goods sold $ (591.9) $ (540.4) $ (1,165.2) [1] $ (1,013.4) [1]
Selling, general and administrative expenses (14.0) (12.3) (26.5) (26.4)
Other operating expense - net (1.5) (1.7) (3.5) (2.2)
Income tax effect 1.3 (0.5) (0.3) (1.0)
Net of tax (4.6) (2.5) 25.1 244.3
Reclassification out of accumulated other comprehensive income | Defined benefit plan and other postretirement liabilities        
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Cost of goods sold 1.5 0.7 2.3 1.6
Selling, general and administrative expenses 0.1 0.1 0.3 0.3
Other operating expense - net 0.0 0.7 0.7 1.4
Income tax effect 0.0 0.0 0.0 0.0
Net of tax 1.6 1.5 3.3 3.3
Reclassification out of accumulated other comprehensive income | Unrealized gain on financial instruments        
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]        
Cost of goods sold (0.1) 0.0 (0.1) (0.1)
Income tax effect 0.0 0.0 0.0 0.0
Net of tax $ (0.1) $ 0.0 $ (0.1) $ (0.1)
[1]
(1) Purchases from related party were $51.8 million and $56.2 million for the three months ended June 30, 2025 and 2024, respectively. Purchases from related parties were $140.1 million and $115.2 million for the six months ended June 30, 2025 and 2024, respectively.
v3.25.2
Components of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Pension Benefits        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Service cost $ 0.6 $ 0.7 $ 1.3 $ 1.3
Interest cost 3.5 3.2 6.8 6.7
Expected return on plan assets (4.0) (4.1) (7.9) (7.9)
Amortization of prior service benefit (cost) 0.0 0.0 0.1 0.1
Amortization of net loss 1.5 1.3 2.9 3.0
Net periodic benefit cost 1.6 1.1 3.2 3.2
Other Postretirement Benefits        
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]        
Service cost 0.1 0.1 0.1 0.1
Interest cost 0.9 0.9 1.9 1.9
Amortization of prior service benefit (cost) 0.0 (0.1) 0.0 (0.1)
Amortization of net loss 0.1 0.3 0.3 0.3
Net periodic benefit cost $ 1.1 $ 1.2 $ 2.3 $ 2.2
v3.25.2
Inventories (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Inventory, Net [Abstract]    
Raw materials $ 178.5 $ 180.8
Work-in-process 50.6 52.1
Finished goods 57.7 74.6
Operating and other supplies 226.6 231.5
Total inventories $ 513.4 $ 539.0
v3.25.2
Fair Value Measurements (Details) - Recurring - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
ASSETS:    
Cash equivalents $ 2.8 $ 7.9
Trust assets 1.1 0.3
Derivative instruments 4.6 4.5
TOTAL 8.5 12.7
LIABILITIES:    
Derivative instruments 19.8 4.4
TOTAL 19.8 4.4
Level 1    
ASSETS:    
Cash equivalents 2.8 7.9
Trust assets 1.1 0.3
Derivative instruments 0.0 0.0
TOTAL 3.9 8.2
LIABILITIES:    
Derivative instruments 0.0 0.0
TOTAL 0.0 0.0
Level 2    
ASSETS:    
Cash equivalents 0.0 0.0
Trust assets 0.0 0.0
Derivative instruments 4.6 4.5
TOTAL 4.6 4.5
LIABILITIES:    
Derivative instruments 19.8 4.4
TOTAL 19.8 4.4
Level 3    
ASSETS:    
Cash equivalents 0.0 0.0
Trust assets 0.0 0.0
Derivative instruments 0.0 0.0
TOTAL 0.0 0.0
LIABILITIES:    
Derivative instruments 0.0 0.0
TOTAL $ 0.0 $ 0.0
v3.25.2
Derivatives - Narrative (Details)
 6 Months Ended
Jun. 30, 2025
USD ($)
Boe
MWh
t
Dec. 31, 2024
USD ($)
Derivative [Line Items]    
Restricted cash | $ $ 0 $ 0
Fixed To Variable London Metals Exchange Swap    
Derivative [Line Items]    
Open position to offset fixed prices (in tonnes) 37,400  
MWP Forward Financial Sales Contracts    
Derivative [Line Items]    
Open position to offset fixed prices (in tonnes) 37,400  
Fixed For Floating Swaps    
Derivative [Line Items]    
Open position to offset fixed prices (in tonnes) 885  
HFO Price Swaps    
Derivative [Line Items]    
Derivative liability (in MwH) | Boe 270,000  
Indiana Hub Power Price Swaps    
Derivative [Line Items]    
Derivative liability (in MwH) | MWh 690,648  
v3.25.2
Derivatives - Assets and Liabilities (Details) - USD ($)
Jun. 30, 2025
Dec. 31, 2024
Related Party    
Derivative [Line Items]    
Due to affiliate, current $ 100,700,000 $ 109,300,000
Commodity contracts | Related Party    
Derivative [Line Items]    
Due to affiliate, current 0 0
Not designated as hedging instrument | Commodity contracts    
Derivative [Line Items]    
Derivative asset 4,600,000 4,500,000
Derivative liability $ 19,800,000 $ 4,400,000
v3.25.2
Derivatives - Net Gain (Loss) (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Derivative [Line Items]        
Derivative gain (loss) on derivative, net $ (15,500,000) $ (4,000,000.0) $ (20,900,000) $ 3,400,000
Commodity contracts        
Derivative [Line Items]        
Derivative gain (loss) on derivative, net (15,500,000) (4,000,000.0) (20,900,000) 3,500,000
Commodity contracts | Related Party | Glencore        
Derivative [Line Items]        
Derivative gain (loss) on derivative, net 0 (1,900,000) 0 2,500,000
Foreign exchange contracts        
Derivative [Line Items]        
Derivative gain (loss) on derivative, net $ 0 $ 0 $ 0 $ (100,000)
v3.25.2
Debt - Activity (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Oct. 01, 2024
Apr. 30, 2021
Debt Instrument [Line Items]        
Total debt $ 488.8 $ 528.2    
Industrial revenue bonds, variable        
Debt Instrument [Line Items]        
Maximum variable interest rate 12.00%      
Hancock County industrial revenue bonds ("IRBs") due April 1, 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 $ 19.6 20.0    
Stated interest rate, percentage 8.00%      
Revolving credit facility | Foreign line of credit        
Debt Instrument [Line Items]        
Revolving credit facility $ 0.0 34.0    
Stated interest rate, percentage 7.82%      
Casthouse Facility | Foreign line of credit        
Debt Instrument [Line Items]        
Revolving credit facility $ 9.0 9.0    
Financing fees 1.0      
Secured debt $ 108.7 114.2    
Stated interest rate, percentage 8.04%      
Vlissingen Credit Facility | Foreign line of credit        
Debt Instrument [Line Items]        
Secured debt $ 10.0 10.0    
Stated interest rate, percentage 7.98%   8.75%  
Senior secured notes, 7.5% | Senior notes        
Debt Instrument [Line Items]        
Financing fees $ 1.6      
Stated interest rate, percentage 7.50%     7.50%
7.5% senior secured notes due April 1, 2028, net of financing fees of $1.6 million at June 30, 2025, interest payable semiannually $ 248.4 248.1    
Senior convertible notes, 2.75% | Senior notes        
Debt Instrument [Line Items]        
Financing fees $ 1.0      
Stated interest rate, percentage 2.75%     2.75%
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.0 million at June 30, 2025, interest payable semiannually $ 85.3 $ 85.1    
Industrial Revenue Bonds Due 2028        
Debt Instrument [Line Items]        
Stated interest rate, percentage 2.05%      
v3.25.2
Debt - Narrative (Details)
 1 Months Ended
Oct. 01, 2024
USD ($)
Nov. 02, 2021
USD ($)
Apr. 30, 2021
USD ($)
$ / shares
Jun. 30, 2025
USD ($)
Dec. 31, 2024
USD ($)
Dec. 09, 2022
USD ($)
Sep. 28, 2022
USD ($)
Jun. 14, 2022
USD ($)
Feb. 04, 2022
USD ($)
Nov. 30, 2013
USD ($)
Senior secured notes, 7.5% | Senior notes                    
Line of Credit Facility [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              
Senior secured notes, 7.5% | Senior notes | Level 2                    
Line of Credit Facility [Line Items]                    
Fair value of debt instrument       $ 254,100,000            
Senior convertible notes, 2.75% | Senior notes                    
Line of Credit Facility [Line Items]                    
Stated interest rate, percentage     2.75% 2.75%            
Face amount     $ 86,300,000              
Percentage of principal amount redeemed     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              
Senior convertible notes, 2.75% | Senior notes | Level 2                    
Line of Credit Facility [Line Items]                    
Fair value of debt instrument       $ 103,300,000            
U.S. revolving credit facility | U.S. revolving credit facility                    
Line of Credit Facility [Line Items]                    
Stated interest rate, percentage       8.00%            
Credit facility maximum amount               $ 250,000,000.0    
Outstanding borrowings       $ 19,600,000            
Outstanding letters of credit issued       47,300,000            
Credit facility maximum amount       $ 250,000,000.0            
U.S. revolving credit facility | Letter of credit                    
Line of Credit Facility [Line Items]                    
Letter of credit sub-facility amount               $ 150,000,000.0    
U.S. revolving credit facility | Foreign line of credit                    
Line of Credit Facility [Line Items]                    
Stated interest rate, percentage       7.82%            
Credit facility maximum amount       $ 100,000,000.0     $ 100,000,000.0     $ 50,000,000
Outstanding borrowings       0            
Outstanding letters of credit issued       0            
Credit facility maximum amount                 $ 80,000,000  
Casthouse Facility                    
Line of Credit Facility [Line Items]                    
Credit facility maximum amount   $ 130,000,000                
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       $ 117,700,000            
Casthouse Facility | Foreign line of credit                    
Line of Credit Facility [Line Items]                    
Stated interest rate, percentage       8.04%            
Secured debt       $ 108,700,000 $ 114,200,000          
Vlissingen Credit Facility | Foreign line of credit                    
Line of Credit Facility [Line Items]                    
Stated interest rate, percentage 8.75%     7.98%            
Face amount           $ 90,000,000        
Credit facility maximum amount $ 90,000,000                  
Term extension 2 years                  
Debt instrument, basis spread on variable rate 3.687%                  
Secured debt       $ 10,000,000.0 $ 10,000,000.0          
Vlissingen Credit Facility | Foreign line of credit | Maximum                    
Line of Credit Facility [Line Items]                    
Variable interest rate 9.00%                  
Vlissingen Credit Facility | Foreign line of credit | Minimum                    
Line of Credit Facility [Line Items]                    
Variable interest rate 7.00%                  
Industrial revenue bonds, variable                    
Line of Credit Facility [Line Items]                    
Maximum variable interest rate       12.00%            
Surety Bond                    
Line of Credit Facility [Line Items]                    
Loss contingency accrual       $ 6,600,000            
v3.25.2
Debt - U.S. Credit Facility Schedule (Details) - U.S. revolving credit facility - Revolving credit facility
$ in Millions
Jun. 30, 2025
USD ($)
Line of Credit Facility [Line Items]  
Credit facility maximum amount $ 250.0
Borrowing availability 208.6
Outstanding letters of credit issued 47.3
Outstanding borrowings 19.6
Borrowing availability, net of borrowings $ 141.8
v3.25.2
Debt - Iceland Credit Facility Schedule (Details) - Foreign line of credit - Revolving credit facility - USD ($)
Jun. 30, 2025
Sep. 28, 2022
Nov. 30, 2013
Line of Credit Facility [Line Items]      
Credit facility maximum amount $ 100,000,000.0 $ 100,000,000.0 $ 50,000,000
Borrowing availability 100,000,000.0    
Outstanding letters of credit issued 0    
Outstanding borrowings 0    
Borrowing availability, net of borrowings $ 100,000,000.0    
v3.25.2
Commitments and Contingencies (Details)
$ in Millions
 1 Months Ended 6 Months Ended 12 Months Ended
Aug. 18, 2017
USD ($)
Oct. 31, 2021
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2025
USD ($)
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       88.00%  
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       38.00%  
Percentage of foreign work force, represented by the union       61.00%  
Contingent consideration, accrued interest and principal       $ 33.0  
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%  
PBGC          
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 and OR          
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       $ 1.8  
v3.25.2
Shareholders’ Equity (Details) - USD ($)
 123 Months Ended
Jun. 30, 2025
Dec. 31, 2024
Mar. 31, 2015
Dec. 31, 2011
Dec. 31, 2008
Class of Stock [Line Items]          
Common stock, shares authorized (in shares) 195,000,000 195,000,000      
Common stock, par value (in dollars per share) $ 0.01 $ 0.01      
Common stock, shares issued (in shares) 100,525,642 100,475,086      
Common stock, shares, outstanding (in shares) 93,339,121 93,288,565      
Preferred stock, shares authorized (in shares) 5,000,000 5,000,000      
Preferred stock par value (in dollars per share) $ 0.01 $ 0.01      
Number of shares issued for each share of preferred stock (in shares) 100        
Stock repurchase program, authorized amount $ 130,000,000.0     $ 60,000,000.0  
Stock repurchase program, authorized, increase amount     $ 70,000,000.0    
Treasury shares acquired (in shares) 7,186,521        
Treasury stock, value $ 86,300,000 $ 86,300,000      
Treasury stock, shares, acquired (in shares) 0        
Stock repurchase program, remaining authorized repurchase amount $ 43,700,000        
Convertible preferred shares          
Class of Stock [Line Items]          
Preferred stock par value (in dollars per share) $ 0.01        
Preferred shares issued (in shares)         160,000
Preferred shares outstanding (in shares) 49,514 49,715      
v3.25.2
Business Segments - Narrative (Details)
 6 Months Ended
Jun. 30, 2025
segment
Segment Reporting [Abstract]  
Number of operating segments 1
Number of reportable segments 1
v3.25.2
Business Segments - Reconciliation of Net Income (Loss) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]        
Net sales $ 628.1 $ 560.8 $ 1,262.0 $ 1,050.3
Selling, general and administrative expenses (14.0) (12.3) (26.5) (26.4)
Other operating expense - net (1.5) (1.7) (3.5) (2.2)
Interest income 1.9 0.6 3.7 1.3
Bargain purchase gain 0.0 0.0 0.0 245.9
Other (loss) income - net (5.7) 1.1 (9.1) (0.4)
Income tax benefit (expense) 1.3 (0.5) (0.3) (1.0)
Net (loss) income (9.1) (6.7) 16.6 238.0
Nonrelated Party        
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]        
Net sales 260.5 236.6 515.7 411.1
Interest expense (9.8) (8.9) (19.8) (16.2)
Net (loss) gain on forward and derivative contracts (15.6) (2.1) (21.0) 0.9
Related Party        
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]        
Net sales 367.6 324.2 746.3 639.2
Interest expense (1.9) (1.4) (3.7) (3.3)
Net (loss) gain on forward and derivative contracts 0.0 (1.9) 0.0 2.5
Reportable Segment        
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]        
Net sales 628.1 560.8 1,262.0 1,050.3
Segment Cost of goods sold (593.2) (532.0) (1,165.6) (1,001.5)
IRA Credit 21.9 10.7 41.8 22.6
Lower of cost or NRV inventory adjustment 1.2 1.7 1.9 7.3
Property and equipment expense (21.8) (20.8) (43.3) (41.8)
Selling, general and administrative expenses (14.0) (12.3) (26.5) (26.4)
Other operating expense - net (1.5) (1.7) (3.5) (2.2)
Interest income 1.9 0.6 3.7 1.3
Bargain purchase gain 0.0 0.0 0.0 245.9
Other (loss) income - net (5.7) 1.1 (9.1) (0.4)
Income tax benefit (expense) 1.3 (0.5) (0.3) (1.0)
Net (loss) income (9.1) (6.7) 16.6 238.0
Reportable Segment | Nonrelated Party        
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]        
Interest expense (9.8) (8.9) (19.8) (16.2)
Net (loss) gain on forward and derivative contracts (15.6) (2.1) (21.0) 0.9
Reportable Segment | Related Party        
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]        
Interest expense (1.9) (1.4) (3.7) (3.3)
Net (loss) gain on forward and derivative contracts $ 0.0 $ (1.9) $ 0.0 $ 2.5
v3.25.2
Variable Interest Entity - Narrative (Details) - Jamalco
Jun. 30, 2025
Variable Interest Entity [Line Items]  
Noncontrolling interest, ownership percentage by parent 55.00%
Percentage of output retained, utilized, or sold by the company 100.00%
Percentage of operations reflected in cash flows 100.00%
Government Of Jamaica  
Variable Interest Entity [Line Items]  
Ownership percentage by noncontrolling owners 45.00%
v3.25.2
Variable Interest Entity - Schedule of consolidated VIE's assets and liabilities (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
ASSETS    
Cash and cash equivalents $ 40.7 $ 32.9
Accounts receivable - net 108.2 75.8
Non-trade receivables 0.0 13.2
Inventories 513.4 539.0
Prepaid and other current assets 25.5 28.3
Total current assets 790.3 802.8
Property, plant and equipment - net 975.6 978.3
Other assets 69.6 87.9
Total assets 1,949.0 1,939.4
LIABILITIES    
Accounts payable, trade 197.7 187.3
Accrued compensation and benefits 44.2 49.8
Accrued and other current liabilities 44.9 42.0
Total current liabilities 451.1 463.7
Accrued benefits costs - less current portion 127.8 130.4
Other liabilities 96.8 92.6
Asset retirement obligations - less current portion 63.2 61.5
Total noncurrent liabilities 813.6 813.0
Variable Interest Entity, Primary Beneficiary    
ASSETS    
Cash and cash equivalents 33.0 17.4
Accounts receivable - net 0.6 1.1
Non-trade receivables 0.0 13.1
Inventories 85.5 109.8
Prepaid and other current assets 5.3 2.0
Total current assets 124.4 218.5
Property, plant and equipment - net 54.5 232.1
Other assets 10.9 23.1
Total assets 189.8 473.7
LIABILITIES    
Accounts payable, trade 43.4 39.1
Accrued compensation and benefits 6.1 8.5
Accrued and other current liabilities 2.7 7.2
Total current liabilities 66.5 104.4
Accrued benefits costs - less current portion 0.0 17.7
Other liabilities 61.9 66.7
Asset retirement obligations - less current portion 10.9 35.0
Total noncurrent liabilities 72.8 119.4
TOTAL 139.3 223.8
Variable Interest Entity, Primary Beneficiary | Related Party    
ASSETS    
Due from affiliates 0.0 75.1
LIABILITIES    
Due to affiliates $ 14.3 $ 49.6
v3.25.2
Subsequent Events (Details) - USD ($)
$ in Millions
Aug. 05, 2025
Aug. 01, 2025
Jul. 22, 2025
Jun. 30, 2025
Oct. 01, 2024
Dec. 09, 2022
Senior Secured Notes Due 2032 | Senior notes | Subsequent Event            
Subsequent Event [Line Items]            
Face amount     $ 400.0      
Stated interest rate, percentage     6.875%      
Proceeds from issuance after financing fees and expenses     $ 395.0      
Senior Notes Due 2028 | Senior notes | Subsequent Event            
Subsequent Event [Line Items]            
Redemption of debt $ 261.1          
Redemption price, percentage 101.875%          
Vlissingen Credit Facility | Foreign line of credit            
Subsequent Event [Line Items]            
Face amount           $ 90.0
Stated interest rate, percentage       7.98% 8.75%  
Vlissingen Credit Facility | Subsequent Event | Foreign line of credit            
Subsequent Event [Line Items]            
Repayments of vilissingen credit facilty   $ 10.0        
U.S. revolving credit facility | Foreign line of credit            
Subsequent Event [Line Items]            
Stated interest rate, percentage       7.82%    
U.S. revolving credit facility | U.S. revolving credit facility            
Subsequent Event [Line Items]            
Stated interest rate, percentage       8.00%    
U.S. revolving credit facility | Subsequent Event | U.S. revolving credit facility            
Subsequent Event [Line Items]            
Basis spread adjustment     0.10%