CENTURY ALUMINUM CO, 10-Q filed on 5/9/2023
Quarterly Report
v3.23.1
Cover - shares
 3 Months Ended
Mar. 31, 2023
May 08, 2023
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2023  
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, $0.01 par value per share  
Entity Trading Symbol CENX  
Security Exchange Name NASDAQ  
Entity Common Stock, Shares Outstanding (in shares)   92,323,978
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Central Index Key 0000949157  
Amendment Flag false  
Document Fiscal Year Focus 2023  
Document Fiscal Period Focus Q1  
Current Fiscal Year End Date --12-31  
v3.23.1
CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)
shares in Millions, $ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
NET SALES:    
Related parties $ 412.2 $ 433.1
Other customers 140.2 320.5
Total net sales 552.4 753.6
Cost of goods sold 504.3 660.4
Gross profit 48.1 93.2
Selling, general and administrative expenses 13.4 11.7
Other operating expense - net 7.2 0.2
Operating income 27.5 81.3
Interest expense (8.7) (7.3)
Interest income 0.3 0.1
Net loss on forward and derivative contracts (57.6) (56.7)
Other (expense) income - net (0.3) 2.0
(Loss) income before income taxes (38.8) 19.4
Income tax benefit (expense) 0.2 (1.7)
Net (loss) income (38.6) 17.7
Less: net income allocated to participating securities 0.0 1.1
Net (loss) income allocated to common stockholders $ (38.6) $ 16.6
(LOSS) INCOME PER COMMON SHARE:    
Basic (in dollars per share) $ (0.42) $ 0.18
Diluted (in dollars per share) $ (0.42) $ 0.18
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:    
Basic (in shares) 92.3 91.2
Diluted (in shares) 92.3 97.1
v3.23.1
CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Comprehensive (loss) income:    
Net (loss) income $ (38.6) $ 17.7
Other comprehensive (loss) income before income tax effect:    
Net (loss) income on foreign currency cash flow hedges reclassified as income (0.1) 0.0
Defined benefit plans and other postretirement benefits:    
Amortization of prior service benefit during the period (0.0) (0.4)
Amortization of net gain during the period 1.2 1.1
Other comprehensive income before income tax effect 1.1 0.7
Income tax effect 0.0 (0.1)
Other comprehensive income 1.1 0.6
Total comprehensive (loss) income $ (37.5) $ 18.3
v3.23.1
CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Millions
Mar. 31, 2023
Dec. 31, 2022
ASSETS    
Cash and cash equivalents $ 30.4 $ 54.3
Restricted cash 1.2 1.2
Accounts receivable - net 47.8 66.9
Due from affiliates 16.5 4.8
Inventories 434.8 398.8
Derivative assets 51.3 127.3
Prepaid and other current assets 22.6 24.5
Total current assets 604.6 677.8
Property, plant and equipment - net 743.2 744.4
Other assets 51.3 49.8
TOTAL 1,399.1 1,472.0
LIABILITIES:    
Accounts payable, trade 149.2 167.3
Due to affiliates 22.6 17.0
Accrued and other current liabilities 53.6 60.7
Derivative liabilities 5.4 9.7
Accrued employee benefits costs 9.9 9.9
Iceland Term Facility 12.3 13.3
U.S. revolving credit facility 63.1 90.0
Iceland revolving credit facility 45.0 35.0
Industrial revenue bonds 7.8 7.8
Total current liabilities 368.9 410.7
Senior notes payable 246.8 246.6
Convertible senior notes payable 84.5 84.4
Grundartangi casthouse debt facility 59.3 49.4
Iceland term facility, net of current portion 0.0 1.2
Accrued pension benefits costs - less current portion 41.8 44.5
Accrued postretirement benefits costs - less current portion 67.2 67.6
Other liabilities 37.1 36.0
Leases - right of use liabilities 21.5 20.9
Due to affiliates - less current portion 5.9 8.3
Deferred taxes 103.7 103.1
Total noncurrent liabilities 667.8 662.0
COMMITMENTS AND CONTINGENCIES (NOTE 11)
SHAREHOLDERS’ EQUITY:    
Preferred stock (Note 7) 0.0 0.0
Common stock (Note 7) 1.0 1.0
Additional paid-in capital 2,540.2 2,539.6
Treasury stock, at cost (86.3) (86.3)
Accumulated other comprehensive loss (92.9) (94.0)
Accumulated deficit (1,999.6) (1,961.0)
Total shareholders’ equity 362.4 399.3
TOTAL $ 1,399.1 $ 1,472.0
v3.23.1
CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES:    
Net (loss) income $ (38.6) $ 17.7
Adjustments to reconcile net (loss) income to net cash (used in) provided by operating activities:    
Unrealized loss on derivative instruments 64.4 35.5
Lower of cost or NRV inventory adjustment 5.1 0.0
Depreciation and amortization 15.9 19.4
Deferred tax (benefit) provision (1.5) 1.3
Other non-cash items - net (0.5) (1.7)
Change in operating assets and liabilities:    
Accounts receivable - net 19.1 (47.1)
Due from affiliates (11.7) (10.3)
Inventories (41.1) (0.9)
Prepaid and other current assets 1.8 (4.2)
Accounts payable, trade (17.4) 31.6
Due to affiliates 10.4 (1.2)
Accrued and other current liabilities (8.7) 1.6
Other - net 2.6 (4.3)
Net cash (used in) provided by operating activities (0.2) 37.4
CASH FLOWS FROM INVESTING ACTIVITIES:    
Purchase of property, plant and equipment (14.3) (26.0)
Proceeds from sales of property, plant and equipment 0.0 0.0
Net cash used in investing activities (14.3) (26.0)
CASH FLOWS FROM FINANCING ACTIVITIES:    
Borrowings under revolving credit facilities 192.4 264.1
Repayments under revolving credit facilities (209.4) (307.4)
Debt issuance costs 0.0 (0.6)
Repayment of Iceland Term Facility (2.4) 0.0
Borrowings under Grundartangi casthouse debt facility 10.0 40.0
Net cash used in financing activities (9.4) (3.9)
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH (23.9) 7.5
Cash, cash equivalents and restricted cash, beginning of period 55.5 40.7
Cash, cash equivalents and restricted cash, end of period 31.6 48.2
Cash paid for:    
Interest 4.0 1.2
Taxes, net of refunds (0.4) 0.5
Non-cash investing activities:    
Capital expenditures 3.9 4.2
Capitalized interest $ 1.0 $ 1.0
v3.23.1
CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ EQUITY - USD ($)
$ in Millions
Total
Preferred stock
Common stock
Additional paid-in capital
Treasury stock, at cost
Accumulated other comprehensive loss
Accumulated deficit
Preferred shares outstanding, period start (in shares) at Dec. 31, 2021   58,542          
Balance, start at Dec. 31, 2021 $ 421.0 $ 0.0 $ 1.0 $ 2,535.5 $ (86.3) $ (82.3) $ (1,946.9)
Beginning balance (in shares) at Dec. 31, 2021     91,231,611        
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Net (loss) income 17.7           17.7
Other comprehensive income 0.6         0.6  
Share-based compensation 0.5     0.5      
Balance, end at Mar. 31, 2022 439.8 $ 0.0 $ 1.0 2,536.0 (86.3) (81.7) (1,929.2)
Ending balance (in shares) at Mar. 31, 2022     91,231,611        
Preferred shares outstanding, period end (in shares) at Mar. 31, 2022   58,542          
Preferred shares outstanding, period start (in shares) at Dec. 31, 2022   53,854          
Balance, start at Dec. 31, 2022 $ 399.3 $ 0.0 $ 1.0 2,539.6 (86.3) (94.0) (1,961.0)
Beginning balance (in shares) at Dec. 31, 2022 92,323,978   92,323,978        
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Net (loss) income $ (38.6)           (38.6)
Other comprehensive income 1.1         1.1  
Share-based compensation 0.6     0.6      
Balance, end at Mar. 31, 2023 $ 362.4 $ 0.0 $ 1.0 $ 2,540.2 $ (86.3) $ (92.9) $ (1,999.6)
Ending balance (in shares) at Mar. 31, 2023 92,323,978   92,323,978        
Preferred shares outstanding, period end (in shares) at Mar. 31, 2023   53,854          
v3.23.1
General
 3 Months Ended
Mar. 31, 2023
Accounting Policies [Abstract]  
General GeneralThe 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, 2022. 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 three months of 2023 are not necessarily indicative of the results that may be expected for the year ending December 31, 2023. 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.
v3.23.1
Curtailment of Operations - Hawesville
 3 Months Ended
Mar. 31, 2023
Restructuring and Related Activities [Abstract]  
Curtailment of Operations - Hawesville Curtailment of Operations - Hawesville
In August 2022, we fully curtailed production at the Hawesville facility and expect to continue to maintain the plant with the intention of restarting operations when market conditions permit, including energy prices returning to more normalized levels and aluminum prices maintaining levels that can support the on-going costs and capital expenditures necessary to restart and operate the plant.
In the first quarter of 2023, we incurred curtailment charges of approximately $7.0 million, including $5.4 million related to excess capacity charges, partially offset by $0.7 million of income related to scrap and materials sales, which are reported in Other operating expense - net, in the Consolidated Statements of Operations.
v3.23.1
Related Party Transactions
 3 Months Ended
Mar. 31, 2023
Related Party Transactions [Abstract]  
Related Party Transactions Related Party Transactions
The significant related party transactions occurring during the three months ended March 31, 2023 and 2022 are described below. We believe all of our transactions with related parties are at prices that approximate market.
Glencore Ownership
As of March 31, 2023, Glencore plc and its affiliates (together "Glencore") beneficially owned 42.9% of Century’s outstanding common stock (46.1% 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 7. 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, purchase and sale of alumina and other raw materials, tolling agreements as well as forward financial contracts and borrowing and other debt transactions.
Sales to Glencore
For the three months ended March 31, 2023 and 2022, we derived approximately 75% and 57% 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 months ended March 31, 2023, we recorded $21.0 million of revenue related to alumina sales to Glencore. There were no alumina sales to Glencore during the three months ended March 31, 2022.
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 months ended March 31, 2023 were priced based on published alumina and aluminum indices as well as fixed prices.
Financial Contracts with Glencore
We have certain financial contracts with Glencore. See Note 14. Derivatives regarding these forward financial sales contracts.
Vlissingen Facility Agreement
On December 9, 2022, Vlissingen entered into a Facility Agreement with Glencore International AG pursuant to which Vlissingen may borrow from time to time up to $90 million (the "Vlissingen Facility Agreement") in one or more loans at a fixed interest rate equal to 8.75% per annum and payable on December 2, 2024. See Note 10. Debt for additional information. Borrowings under the Vlissingen Facility Agreement are expected to be used for general corporate and working capital purposes of Century and its subsidiaries.
Summary
A summary of the aforementioned significant related party transactions is as follows: 
 Three months ended March 31,
 20232022
Net sales to Glencore$412.2 $433.1 
Purchases from Glencore(1)
76.1 54.5 

(1) Includes settlements of financial contract positions.
v3.23.1
Revenue
 3 Months Ended
Mar. 31, 2023
Revenue Recognition and Deferred Revenue [Abstract]  
Revenue Revenue
We disaggregate our revenue by geographical region as follows:
Net SalesThree months ended March 31,
20232022
United States$342.3 $506.1 
Iceland210.1 247.5 
Total$552.4 $753.6 
v3.23.1
Fair Value Measurements
 3 Months Ended
Mar. 31, 2023
Fair Value Disclosures [Abstract]  
Fair Value Measurements Fair Value Measurements
We measure certain of our assets and liabilities at fair value. Fair value represents the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.
In general, reporting entities should apply valuation techniques to measure fair value that maximize the use of observable inputs and minimize the use of unobservable inputs. Observable inputs are developed using market data and reflect assumptions that market participants would use when pricing the asset or liability. Unobservable inputs are developed using the best information available about the assumptions 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 March 31, 2023
Level 1
Level 2
Level 3
Total
ASSETS:
Cash equivalents$7.2 $— $— $7.2 
Trust assets(1)
1.5 — — 1.5 
Derivative instruments— 52.6 — 52.6 
TOTAL$8.7 $52.6 $— $61.3 
LIABILITIES:
Derivative instruments— (19.3)— (19.3)
TOTAL$— $(19.3)$— $(19.3)

Recurring Fair Value Measurements
As of December 31, 2022
Level 1
Level 2
Level 3
Total
ASSETS:
Cash equivalents$5.6 $— $— $5.6 
Trust assets(1)
0.1— — 0.1
Derivative instruments— 127.3 1.8 129.1 
TOTAL$5.7 $127.3 $1.8 $134.8 
LIABILITIES:
Derivative instruments$— $26.4 $4.6 $31.0 
TOTAL$— $26.4 $4.6 $31.0 
(1) Trust assets are currently invested in money market funds. These trust assets are held to fund the non-qualified supplemental executive pension benefit obligations for certain of our officers.
The following section describes the valuation techniques and inputs for fair value measurements categorized within Level 2 or Level 3 of the fair value hierarchy:
Level 2 Fair Value Measurements:
Asset / LiabilityValuation TechniquesInputs
LME forward financial sales contractsDiscounted cash flowsQuoted LME forward market
Midwest Premium ("MWP") forward financial sales contracts Discounted cash flowsQuoted MWP forward market
Fixed for floating swapsDiscounted cash flowsQuoted LME forward market, quoted MWP forward market
Nord Pool power price swaps Discounted cash flowsQuoted Nord Pool forward market
Indiana Hub power price swapsDiscounted cash flowsQuoted Indiana Hub forward market
FX swaps Discounted cash flowsEuro/USD forward exchange rate
Casthouse currency hedgesDiscounted cash flowsEuro/USD forward exchange rate; ISK/USD forward exchange rate
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.
The following table presents the inputs for recurring fair value measurements categorized within Level 3 of the fair value hierarchy, along with information regarding significant unobservable inputs used to value Level 3 assets and liabilities:
Recurring Level 3 Fair Value Measurements:
As of March 31, 2023
As of December 31, 2022
Asset / LiabilityValuation TechniqueObservable InputsSignificant Unobservable InputFair Value Value/Range of Unobservable InputFair ValueValue/Range of Unobservable Input
LME forward financial sales contractsDiscounted cash flowsQuoted LME forward market
Discount rate net(1)
$— 8.58%$(2.8)8.58%
(1) Represents risk adjusted discount rate.
The following table presents the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis.

For the three months ended March 31, 2023
Level 3 AssetsLevel 3 Liabilities
LME forward financial sales contractsLME forward financial sales contracts
Balance as of December 31, 2022$1.8 $(4.6)
Transfers out of Level 3(1)
(1.8)4.6 
Balance as of March 31, 2023
$— $— 
Change in unrealized gains (losses)(2)
$— $— 

(1) Transfers out of Level 3 due to period of time remaining in derivative contract.
(2) Gains and losses are presented in the Consolidated Statement of Operations within the line item "Net loss on forward and derivative contracts."
Level 3 AssetsLevel 3 Liabilities
For the three months ended March 31, 2022
Nord Pool SwapsLME forward financial sales contractsFX Swaps
Balance as of December 31, 2021$0.2 $(5.1)$(0.2)
Total realized/unrealized loss
     Included in net income (loss)(1)
— (9.1)— 
Transfers into Level 3(2)
— (2.5)— 
Transfers out of Level 3(3)
(0.2)(0.0)0.2 
Balance as of March 31, 2022
$— $(16.7)$— 
Change in unrealized gains (losses)(1)
$— $(9.1)$— 
(1) Gains and losses are presented in the Consolidated Statement of Operations within the line item "Net loss on forward and derivative contracts."
(2) Transfers into Level 3 due to contracts with applied discount rate entered into during the three months ended March 31, 2022.
(3) Transfers out of Level 3 due to period of time remaining in derivative contract.
v3.23.1
(Loss) Earnings Per Share
 3 Months Ended
Mar. 31, 2023
Earnings Per Share [Abstract]  
(Loss) Earnings Per Share (Loss) Earnings Per Share
Basic (loss) earnings per share ("EPS") amounts are calculated by dividing net (loss) income allocated to common stockholders by the weighted average number of common shares outstanding during the period. Diluted EPS amounts assume the issuance of common stock for all potentially dilutive securities.
The following table shows the basic and diluted (loss) earnings per share:
For the three months ended March 31,
2023
2022
Net Loss
Shares
(in millions)
Per ShareNet Income
Shares
(in millions)
Per Share
Net (loss) income$(38.6)$17.7 
Less: net income allocated to participating securities— 1.1 
Basic EPS:
Net (loss) income allocated to common stockholders$(38.6)92.3 $(0.42)$16.6 91.2 $0.18 
Effect of Dilutive Securities(1):
Share-based compensation— — — 1.1 
Convertible senior notes— — 0.7 4.8 
Diluted EPS:
Net (loss) income allocated to common stockholders with assumed conversion$(38.6)92.3 $(0.42)$17.3 97.1 $0.18 

Three months ended March 31,
Securities excluded from the calculation of diluted EPS (in millions)(1):
20232022
Share-based compensation - TVPSU0.6 — 
Share-based compensation - PSU0.3 0.7 
Convertible preferred shares5.4 5.9 
Convertible notes4.6 — 
(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.
v3.23.1
Shareholders’ Equity
 3 Months Ended
Mar. 31, 2023
Stockholders' Equity Note [Abstract]  
Shareholders’ Equity Shareholders’ Equity
Common Stock
As of March 31, 2023 and December 31, 2022, we had 195,000,000 shares of common stock, $0.01 par value per share, authorized under our Restated Certificate of Incorporation, of which 99,510,499 shares were issued and 92,323,978 shares were outstanding.
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 March 31, 2023 and December 31, 2022, we had 5,000,000 shares of preferred stock, $0.01 cent par value per share, authorized under our Restated Certificate of Incorporation. Our Board of Directors may issue preferred stock in one or more series and determine for each series the dividend rights, conversion rights, voting rights, redemption rights, 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. Glencore holds all of the issued and outstanding Series A Convertible Preferred Stock. At March 31, 2023 and December 31, 2022, 53,854 shares were outstanding.
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.  
There were no preferred stock conversions during the three months ended March 31, 2023 and March 31, 2022.
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.
We have repurchased 7,186,521 shares of common stock under the program 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 March 31, 2023.
v3.23.1
Income Taxes
 3 Months Ended
Mar. 31, 2023
Income Tax Disclosure [Abstract]  
Income Taxes Income Taxes
For the three months ended March 31, 2023 and March 31, 2022, we recorded an income tax benefit of $0.2 million and an income tax expense of $1.7 million, respectively. The change is primarily due to tax impacts from foreign operations in each period.
Our income tax benefit or expense is based on an annual effective tax rate forecast, including estimates and assumptions that could change during the year. 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 pre-tax accounting income/loss as reported on the consolidated statement of operations.
As of March 31, 2023, all of Century's U.S. and certain foreign deferred tax assets, net of deferred tax liabilities, continue to be subject to a valuation allowance.
The Inflation Reduction Act of 2022 ("IRA") was signed into law on August 16, 2022, and the CHIPS and Science Act of 2022 was signed into law on August 9, 2022. These laws implement new tax provisions, primarily a 15% corporate alternative minimum tax and a nondeductible 1% excise tax on the fair market value of stock repurchased by publicly traded corporations. As of March 31, 2023, these provisions, which were effective January 1, 2023, have not had any material impact on the financial statements. The IRA provides several tax incentives to promote clean energy and the production of critical minerals in the U.S. We are continuing to evaluate potential tax benefits available under the acts as additional guidance is issued.
v3.23.1
Inventories
 3 Months Ended
Mar. 31, 2023
Inventory, Net [Abstract]  
Inventories InventoriesInventories consist of the following:
March 31, 2023December 31, 2022
Raw materials$98.8 $64.9 
Work-in-process47.8 46.0 
Finished goods43.4 58.0 
Operating and other supplies244.8 229.9 
Total inventories$434.8 $398.8 
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.
v3.23.1
Debt
 3 Months Ended
Mar. 31, 2023
Debt Disclosure [Abstract]  
Debt Debt
March 31, 2023December 31, 2022
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)
63.1 90.0 
  Iceland Revolving Credit Facility(3)
45.0 35.0 
Iceland Term Facility(5)
12.3 13.3
Debt classified as non-current liabilities:
Grundartangi casthouse facility, net of financing fees of $0.6 million at March 31, 2023(4)
59.3 49.4 
Iceland Term Facility, net of financing fees of $0.00 million and current portion at March 31, 2023(5)
— 1.2 
7.5% senior secured notes due April 1, 2028, net of financing fees of $3.2 million at March 31, 2023, interest payable semiannually
246.8 246.6 
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.8 million at March 31, 2023, interest payable semiannually
84.5 84.4 
Total$518.8 $527.7 
(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 March 31, 2023 was 4.11%.
(2) We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at March 31, 2023 was 8.75%.
(3) We incur interest at base rate plus applicable margin as defined within the agreement. The interest rate at March 31, 2023 was 7.66%.
(4) We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at March 31, 2023 was 8.08%.
(5) We incur interest at a rate equal to 3.2% plus EUR EURIBOR 1 month as published by the European Money Market Institute as defined within the agreement. The interest rate at March 31, 2023 was 5.77%.
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 March 31, 2023, the total estimated fair value of the 2028 Notes was $237.8 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.
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, which began on November 1, 2021, 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 March 31, 2023, 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 March 31, 2023, the if-converted value of the Convertible Notes does not exceed the outstanding principal amount.
As of March 31, 2023, the total estimated fair value of the Convertible Notes was $70.7 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 March 31, 2023, there were $63.1 million in outstanding borrowings and $41.1 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:March 31, 2023
Credit facility maximum amount$250.0 
Borrowing availability169.8 
Outstanding letters of credit issued41.1 
Outstanding borrowings63.1 
Borrowing availability, net of outstanding letters of credit and borrowings65.6 
Iceland Revolving Credit Facility
Our wholly-owned subsidiary, Nordural Grundartangi ehf ("Grundartangi"), has entered into a $80.0 million revolving credit facility agreement with Landsbankinn hf., dated November 2013, as amended (the "Iceland revolving credit facility"). 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 March 31, 2023, there were $45.0 million in outstanding borrowings under our Iceland revolving credit facility. The Iceland revolving credit facility has a term through November 2024.
Status of our Iceland revolving credit facility:March 31, 2023
Credit facility maximum amount$100.0 
Borrowing availability100.0 
Outstanding letters of credit issued— 
Outstanding borrowings45.0 
Borrowing availability, net of borrowings55.0 
Grundartangi Casthouse Facility
Our wholly-owned subsidiary, Grundartangi, has entered into an eight-year Term Facility Agreement with Arion Bank hf, dated November 2021, as amended (the "Casthouse Facility") to provide for borrowings up to $130.0 million associated with construction of the new billet casthouse at Grundartangi (the"casthouse project"). 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 March 31, 2023, there were $60.0 million in outstanding borrowings under the Casthouse Facility.
Iceland Term Facility
Our wholly-owned subsidiary, Grundartangi, has entered into a Term Facility Agreement with Arion Bank hf, dated September 2022, (the "Iceland Term Facility") to provide for borrowings up to €13.6 million. Repayments of principal amounts are made in equal monthly installments, the first payment occurring in February 2023, with the remainder of the principal amount to be paid no later than the termination date in January 2024. Borrowings under the Iceland Term Facility bear interest at a rate equal to 3.2% plus EUR EURIBOR 1 month as published at any time by the European Money Markets Institute. As of March 31, 2023, there were €11.3 million ($12.3 million, based on the prevailing exchange rate on March 31, 2023) in outstanding borrowings under the Iceland Term Facility.
Vlissingen Facility Agreement
On December 9, 2022, Vlissingen entered into a Facility Agreement with Glencore International AG pursuant to which Vlissingen may borrow from time to time up to $90 million (the "Vlissingen Facility Agreement") in one or more loans payable on December 2, 2024, the maturity date of the Vlissingen Facility Agreement. As of March 31, 2023, there were no outstanding borrowings under the Vlissingen Facility Agreement.
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 March 31, 2023, 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.
v3.23.1
Commitments and Contingencies
 3 Months Ended
Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Commitments and Contingencies
We have pending against us or may be subject to various lawsuits, claims and proceedings related primarily to employment, commercial, stockholder, environmental, safety and health matters and are involved in other matters that may give rise to contingent liabilities. While the results of such matters and claims cannot be predicted with certainty, we believe that the ultimate outcome of any such matters and claims will not have a material adverse impact on our financial condition, results of operations or liquidity. However, because of the nature and inherent uncertainties of litigation and estimating liabilities, should the resolution or outcome of these actions be unfavorable, our business, financial condition, results of operations and liquidity could be materially and adversely affected.
In evaluating whether to accrue for losses associated with legal or environmental contingencies, it is our policy to take into consideration factors such as the facts and circumstances asserted, our historical experience with contingencies of a similar nature, the likelihood of our prevailing and the severity of any potential loss. For some matters, no accrual is established because we have assessed our risk of loss to be remote. Where the risk of loss is probable and the amount of the loss can be reasonably estimated, we record an accrual, either on an individual basis or with respect to a group of matters involving similar claims, based on the factors set forth above. While we regularly review the status of, and our estimates of potential liability
associated with, contingencies to determine the adequacy of any associated accruals and related disclosures, the ultimate amount of loss may differ from our estimates.
Legal Contingencies
Ravenswood Retiree Medical Benefits
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 which 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 ten 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 March 31, 2023, $2.0 million was recorded in other current liabilities and $4.9 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 did not make any contributions for the three month periods ended March 31, 2023, or 2022. 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 March 31, 2023, we made contributions of $2.4 million related to the Amended PBGC Settlement Agreement.
Power Commitments and Contingencies
Hawesville
Hawesville has a power supply arrangement with Kenergy and EDF Trading North America, LLC (“EDF") which provides market-based power to the Hawesville smelter. Under this arrangement, the power companies purchase power on the open market and pass it through to Hawesville at Midcontinent Independent System Operator ("MISO") pricing plus transmission and other costs. The power supply arrangement with Kenergy has an effective term through December 2023. The arrangement with EDF to act as our market participant with MISO has an effective term through May 2023. On April 26, 2022 EDF gave notice that it would no longer serve as the MISO Market Participant for Hawesville. The notice terminated EDF’s contract, effective May 31, 2023, to purchase power from MISO for resale to Kenergy, which then resells the power to Hawesville.

In connection with the temporary curtailment of production at Hawesville, energy use at the smelter has been significantly reduced. However, such reduction in energy use does not reduce Hawesville’s capacity payment obligation to MISO which extends through May 2023. Century currently expects to act as its own MISO Market Participant (through an indirect, wholly-owned subsidiary) after May 31, 2023.
Sebree
Sebree has a power supply arrangement with Kenergy and EDF which provides market-based power to the Sebree smelter. Similar to the arrangement at Hawesville, the power companies purchase power on the open market and pass it through to Sebree at MISO pricing plus transmission and other costs. The power supply arrangement with Kenergy has an effective term through December 2023. The arrangement with EDF to act as our market participant with MISO has an effective term through May 2023. On April 26, 2022 EDF gave notice that it would no longer serve as the MISO Market Participant for Sebree. The notice terminated EDF’s contract, effective May 31, 2023, to purchase power from MISO for resale to Kenergy, which then resells the power to Sebree. Century currently expects to act as its own MISO Market Participant (through an indirect, wholly-owned subsidiary) after May 31, 2023.
Mt. Holly
Century Aluminum of South Carolina, Inc. has a power supply agreement with Santee Cooper that has an effective term from April 1, 2021 through December 2023. 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. The contract provides sufficient energy to allow Mt. Holly to produce at 75% of full production capacity.
Grundartangi
Grundartangi has power purchase agreements for approximately 545 MW with HS Orka hf ("HS"), Landsvirkjun and Orkuveita Reykjavikur ("OR") to provide power to its Grundartangi smelter. These power purchase agreements expire on various dates from 2026 through 2036 (subject to extension). The power purchase agreements with HS and OR provide power at LME-based variable rates for the duration of these agreements. In July 2021, Grundartangi reached an agreement with Landsvirkjun for an extension of its existing 161 MW power contract that would have expired in December 2023. Under the terms of the extension, Landsvirkjun will continue to supply power to Grundartangi from January 1, 2024 through December 31, 2026 and will increase the existing contract from 161 MW to 182 MW over time to provide the necessary flexibility to support the most recent capacity creep requirements and future growth opportunities for value-added products at the Grundartangi plant, including the Grundartangi casthouse project. In September 2022, this agreement was amended to provide for 42 MW at a fixed price and 119 MW at rates linked to Nord Pool plus transmission through 2023 and beginning January 1, 2024 through December 31, 2026, this agreement allows for fixed rates plus a small variable rate portion of the full 182 MW. Grundartangi also has a 25 MW power purchase agreement with Landsvirkjun at LME-based variable rates.
Other Commitments and Contingencies
Labor Commitments
The bargaining unit employees at our Grundartangi, Vlissingen, Hawesville and Sebree facilities are represented by labor unions, representing approximately 58% of our total workforce. 
Approximately 87% 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 is effective through December 31, 2024.
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 May 31, 2024.

Approximately 42% 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 temporary 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, 2023. Mt. Holly employees are not represented by a labor union.
Contingent obligations
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 March 31, 2023, the principal and accrued interest for the contingent obligation was $29.8 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. As of March 31, 2023, the LME forward market prices do not exceed the threshold for payment. In addition, based on the current level of Hawesville's operations, including the temporary curtailment, we believe that we will not be required to make payments on the contingent obligation during the term of the agreement, which expires in 2028. There can be no assurance that circumstances will not change thus accelerating the timing of such payments.
v3.23.1
Components of Accumulated Other Comprehensive Loss
 3 Months Ended
Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]  
Components of Accumulated Other Comprehensive Loss Components of Accumulated Other Comprehensive Loss
Components of AOCL:
March 31, 2023
December 31, 2022
Defined benefit plan liabilities
$(96.8)$(98.0)
Unrealized gain (loss) on financial instruments
1.7 1.7 
Other comprehensive loss before income tax effect
(95.1)(96.3)
Income tax effect(1)
2.2 2.3 
Accumulated other comprehensive loss
$(92.9)$(94.0)
(1) The allocation of the income tax effect to the components of other comprehensive loss is as follows:
March 31, 2023
December 31, 2022
Defined benefit plan liabilities$2.6 $2.6 
Unrealized loss on financial instruments(0.3)(0.3)
The following table summarizes the changes in the accumulated balances for each component of AOCL:
Defined benefit plan and other postretirement liabilitiesUnrealized gain (loss) on financial instrumentsTotal, net of tax
Balance, January 1, 2023$(95.6)$1.6 $(94.0)
Net amount reclassified to net income (loss)1.2 (0.1)1.1 
Balance, March 31, 2023
$(94.4)$1.5 $(92.9)
Balance, January 1, 2022$(84.0)$1.7 $(82.3)
Net amount reclassified to net income (loss)0.6 0.0 0.6 
Balance, March 31, 2022
$(83.4)$1.7 $(81.7)

Reclassifications out of AOCL were included in the consolidated statements of operations as follows:
Three months ended March 31,
AOCL ComponentsLocation20232022
Defined benefit plan and other postretirement liabilitiesCost of goods sold$0.8 $0.4 
Selling, general and administrative expenses0.2 0.1 
Other operating expense - net0.2 0.2 
Income tax effect— (0.1)
Net of tax$1.2 $0.6 
Unrealized loss on financial instrumentsCost of goods sold$(0.1)$0.0 
Income tax effect0.0 0.0 
Net of tax$(0.1)$0.0 
v3.23.1
Components of Net Periodic Benefit Cost
 3 Months Ended
Mar. 31, 2023
Retirement Benefits [Abstract]  
Components of Net Periodic Benefit Cost Components of Net Periodic Benefit Cost
Pension Benefits
Three months ended March 31,
20232022
Service cost$1.1 $1.1 
Interest cost2.6 2.5 
Expected return on plan assets(5.9)(5.8)
Amortization of prior service costs0.0 — 
Amortization of net loss0.9 0.7 
Net periodic benefit cost (income)$(1.3)$(1.5)
Other Postretirement Benefits
Three months ended March 31,
20232022
Service cost$0.0 $0.1 
Interest cost0.7 0.7 
Amortization of prior service cost0.0 (0.5)
Amortization of net loss0.3 0.5 
Net periodic benefit cost (income)$1.0 $0.8 
v3.23.1
Derivatives
 3 Months Ended
Mar. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Derivatives Derivatives
As of March 31, 2023, we had an open position of 70,464 tonnes related to LME forward financial sales contracts to fix the forward LME aluminum price. These contracts are expected to settle monthly through December 2024. We have also entered 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 March 31, 2023, we had 2,878 tonnes related to fixed for floating swaps that will settle monthly through November 2023.
We have entered into financial contracts to hedge a portion of Grundartangi's exposure to the Nord Pool power market (“Nord Pool power price swaps”). All of the Nord Pool power price swaps are expected to cash settle monthly through December 2023. The Nord Pool power price swaps are settled in Euros, therefore we have entered into financial contracts to hedge the risk of fluctuations associated with the Euro ("FX swaps"). As of March 31, 2023, we had an open position related to the FX swaps of €24.5 million that will settle monthly through December 2023.
During the third quarter of 2022, we entered certain floating Nord Pool financial contracts to unwind a portion of our fixed contract position as a result of the recent power agreement amendment, making us predominantly hedged against Nord Pool power price fluctuations during 2023. As of March 31, 2023, we had an open net position of 745,908 MWh related to the Nord Pool power price swaps.
We have entered into financial contracts to fix a portion of our exposure to the Indiana Hub power market at our Kentucky plants ("Indiana Hub power price swaps"). As of March 31, 2023, we had an open position of 132,000 MWh. The Indiana Hub power price swaps are expected to settle monthly through December 2023.
We have entered into forward contracts to hedge the risk of fluctuations associated with the Icelandic Krona (ISK) and Euro for contracts related to the construction of the Grundartangi casthouse denominated in these currencies ("casthouse currency hedges"). As of March 31, 2023, we had an open position related to the ISK casthouse swaps of kr4,346.7 million that will settle monthly through July 2023. As of March 31, 2023, we had an open position related to the Euro casthouse swaps of €7.6 million that will settle monthly through February 2024.
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 March 31,
2023 and December 31, 2022, the Company had not recorded restricted cash as collateral related to open derivative contracts under the master arrangements with our counterparties.
The following tables sets forth the Company's derivative assets and liabilities that were accounted for at fair value and not designated as cash flow hedges as of March 31, 2023 and December 31, 2022, respectively:
 Asset Fair Value
March 31, 2023December 31, 2022
Commodity contracts(1)
$52.5 $129.1 
Foreign exchange contracts(2)
0.1 — 
Total$52.6 $129.1 
 Liability Fair Value
March 31, 2023December 31, 2022
Commodity contracts(1)
$15.1 $23.7 
Foreign exchange contracts(2)
4.2 7.3 
Total$19.3 $31.0 
(1) Commodity contracts reflect our outstanding LME forward financial sales contracts, MWP forward financial sales contracts, fixed for floating swaps, Nord Pool power price swaps, and Indiana Hub power price swaps. At March 31, 2023, $7.1 million of Due to affiliates, and $5.9 million of Due to affiliates - less current portion were related to commodity contracts with Glencore. At December 31, 2022, $11.9 million of Due to affiliates, and $8.3 million of Due to affiliates - less current portion were related to commodity contract liabilities with Glencore.
(2) Foreign exchange contracts reflect our outstanding FX swaps and the casthouse currency hedges.
The following table summarizes the net loss on forward and derivative contracts:
Three months ended March 31,
20232022
Commodity contracts(1)
$(59.1)$(56.0)
Foreign exchange contracts1.6 (1.0)
   Total$(57.5)$(57.0)
(1) For the three months ended March 31, 2023, $14.9 million of the net loss was with Glencore, and for the three months ended March 31, 2022, $58.9 million of the net loss was with Glencore.
v3.23.1
Subsequent Events
 3 Months Ended
Mar. 31, 2023
Subsequent Events [Abstract]  
Subsequent Events Subsequent EventsOn May 2, 2023, our newly-formed, wholly-owned subsidiary, Century Aluminum Jamaica Holdings, Inc., a Delaware corporation ("Century Jamaica"), purchased for $1.00 a 55% interest in Jamalco, an unincorporated joint venture engaged in bauxite mining and alumina production in Jamaica. The remaining 45% interest in Jamalco is owned by Clarendon Alumina Production Limited ("CAP"), which in turn is owned by the Government of Jamaica.
v3.23.1
Related Party Transactions (Tables)
 3 Months Ended
Mar. 31, 2023
Related Party Transactions [Abstract]  
Schedule of related party transactions
A summary of the aforementioned significant related party transactions is as follows: 
 Three months ended March 31,
 20232022
Net sales to Glencore$412.2 $433.1 
Purchases from Glencore(1)
76.1 54.5 

(1) Includes settlements of financial contract positions.
v3.23.1
Revenue (Tables)
 3 Months Ended
Mar. 31, 2023
Revenue Recognition and Deferred Revenue [Abstract]  
Disaggregation of revenue by geographical region
We disaggregate our revenue by geographical region as follows:
Net SalesThree months ended March 31,
20232022
United States$342.3 $506.1 
Iceland210.1 247.5 
Total$552.4 $753.6 
v3.23.1
Fair Value Measurements (Tables)
 3 Months Ended
Mar. 31, 2023
Fair Value Disclosures [Abstract]  
Financial assets and liabilities at fair value on a recurring basis
Recurring Fair Value Measurements
As of March 31, 2023
Level 1
Level 2
Level 3
Total
ASSETS:
Cash equivalents$7.2 $— $— $7.2 
Trust assets(1)
1.5 — — 1.5 
Derivative instruments— 52.6 — 52.6 
TOTAL$8.7 $52.6 $— $61.3 
LIABILITIES:
Derivative instruments— (19.3)— (19.3)
TOTAL$— $(19.3)$— $(19.3)

Recurring Fair Value Measurements
As of December 31, 2022
Level 1
Level 2
Level 3
Total
ASSETS:
Cash equivalents$5.6 $— $— $5.6 
Trust assets(1)
0.1— — 0.1
Derivative instruments— 127.3 1.8 129.1 
TOTAL$5.7 $127.3 $1.8 $134.8 
LIABILITIES:
Derivative instruments$— $26.4 $4.6 $31.0 
TOTAL$— $26.4 $4.6 $31.0 
(1) Trust assets are currently invested in money market funds. These trust assets are held to fund the non-qualified supplemental executive pension benefit obligations for certain of our officers.
Schedule of valuation methodology for assets and liabilities at fair value The following section describes the valuation techniques and inputs for fair value measurements categorized within Level 2 or Level 3 of the fair value hierarchy:
Level 2 Fair Value Measurements:
Asset / LiabilityValuation TechniquesInputs
LME forward financial sales contractsDiscounted cash flowsQuoted LME forward market
Midwest Premium ("MWP") forward financial sales contracts Discounted cash flowsQuoted MWP forward market
Fixed for floating swapsDiscounted cash flowsQuoted LME forward market, quoted MWP forward market
Nord Pool power price swaps Discounted cash flowsQuoted Nord Pool forward market
Indiana Hub power price swapsDiscounted cash flowsQuoted Indiana Hub forward market
FX swaps Discounted cash flowsEuro/USD forward exchange rate
Casthouse currency hedgesDiscounted cash flowsEuro/USD forward exchange rate; ISK/USD forward exchange rate
The following table presents the inputs for recurring fair value measurements categorized within Level 3 of the fair value hierarchy, along with information regarding significant unobservable inputs used to value Level 3 assets and liabilities:
Recurring Level 3 Fair Value Measurements:
As of March 31, 2023
As of December 31, 2022
Asset / LiabilityValuation TechniqueObservable InputsSignificant Unobservable InputFair Value Value/Range of Unobservable InputFair ValueValue/Range of Unobservable Input
LME forward financial sales contractsDiscounted cash flowsQuoted LME forward market
Discount rate net(1)
$— 8.58%$(2.8)8.58%
(1) Represents risk adjusted discount rate.
Schedule of fair value reconciliation of Level 3 assets and liabilities measured at fair value
The following table presents the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis.

For the three months ended March 31, 2023
Level 3 AssetsLevel 3 Liabilities
LME forward financial sales contractsLME forward financial sales contracts
Balance as of December 31, 2022$1.8 $(4.6)
Transfers out of Level 3(1)
(1.8)4.6 
Balance as of March 31, 2023
$— $— 
Change in unrealized gains (losses)(2)
$— $— 

(1) Transfers out of Level 3 due to period of time remaining in derivative contract.
(2) Gains and losses are presented in the Consolidated Statement of Operations within the line item "Net loss on forward and derivative contracts."
Level 3 AssetsLevel 3 Liabilities
For the three months ended March 31, 2022
Nord Pool SwapsLME forward financial sales contractsFX Swaps
Balance as of December 31, 2021$0.2 $(5.1)$(0.2)
Total realized/unrealized loss
     Included in net income (loss)(1)
— (9.1)— 
Transfers into Level 3(2)
— (2.5)— 
Transfers out of Level 3(3)
(0.2)(0.0)0.2 
Balance as of March 31, 2022
$— $(16.7)$— 
Change in unrealized gains (losses)(1)
$— $(9.1)$— 
(1) Gains and losses are presented in the Consolidated Statement of Operations within the line item "Net loss on forward and derivative contracts."
(2) Transfers into Level 3 due to contracts with applied discount rate entered into during the three months ended March 31, 2022.
(3) Transfers out of Level 3 due to period of time remaining in derivative contract.
v3.23.1
(Loss) Earnings Per Share (Tables)
 3 Months Ended
Mar. 31, 2023
Earnings Per Share [Abstract]  
Basic and diluted earnings (loss) per share and securities excluded from the calculation of diluted EPS The following table shows the basic and diluted (loss) earnings per share:
For the three months ended March 31,
2023
2022
Net Loss
Shares
(in millions)
Per ShareNet Income
Shares
(in millions)
Per Share
Net (loss) income$(38.6)$17.7 
Less: net income allocated to participating securities— 1.1 
Basic EPS:
Net (loss) income allocated to common stockholders$(38.6)92.3 $(0.42)$16.6 91.2 $0.18 
Effect of Dilutive Securities(1):
Share-based compensation— — — 1.1 
Convertible senior notes— — 0.7 4.8 
Diluted EPS:
Net (loss) income allocated to common stockholders with assumed conversion$(38.6)92.3 $(0.42)$17.3 97.1 $0.18 

Three months ended March 31,
Securities excluded from the calculation of diluted EPS (in millions)(1):
20232022
Share-based compensation - TVPSU0.6 — 
Share-based compensation - PSU0.3 0.7 
Convertible preferred shares5.4 5.9 
Convertible notes4.6 — 
(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.
v3.23.1
Inventories (Tables)
 3 Months Ended
Mar. 31, 2023
Inventory, Net [Abstract]  
Schedule of inventories Inventories consist of the following:
March 31, 2023December 31, 2022
Raw materials$98.8 $64.9 
Work-in-process47.8 46.0 
Finished goods43.4 58.0 
Operating and other supplies244.8 229.9 
Total inventories$434.8 $398.8 
v3.23.1
Debt (Tables)
 3 Months Ended
Mar. 31, 2023
Debt Disclosure [Abstract]  
Schedule of debt
March 31, 2023December 31, 2022
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)
63.1 90.0 
  Iceland Revolving Credit Facility(3)
45.0 35.0 
Iceland Term Facility(5)
12.3 13.3
Debt classified as non-current liabilities:
Grundartangi casthouse facility, net of financing fees of $0.6 million at March 31, 2023(4)
59.3 49.4 
Iceland Term Facility, net of financing fees of $0.00 million and current portion at March 31, 2023(5)
— 1.2 
7.5% senior secured notes due April 1, 2028, net of financing fees of $3.2 million at March 31, 2023, interest payable semiannually
246.8 246.6 
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.8 million at March 31, 2023, interest payable semiannually
84.5 84.4 
Total$518.8 $527.7 
(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 March 31, 2023 was 4.11%.
(2) We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at March 31, 2023 was 8.75%.
(3) We incur interest at base rate plus applicable margin as defined within the agreement. The interest rate at March 31, 2023 was 7.66%.
(4) We incur interest at a base rate plus applicable margin as defined within the agreement. The interest rate at March 31, 2023 was 8.08%.
(5) We incur interest at a rate equal to 3.2% plus EUR EURIBOR 1 month as published by the European Money Market Institute as defined within the agreement. The interest rate at March 31, 2023 was 5.77%.
Schedule of line of credit facilities
Status of our U.S. revolving credit facility:March 31, 2023
Credit facility maximum amount$250.0 
Borrowing availability169.8 
Outstanding letters of credit issued41.1 
Outstanding borrowings63.1 
Borrowing availability, net of outstanding letters of credit and borrowings65.6 
Status of our Iceland revolving credit facility:March 31, 2023
Credit facility maximum amount$100.0 
Borrowing availability100.0 
Outstanding letters of credit issued— 
Outstanding borrowings45.0 
Borrowing availability, net of borrowings55.0 
v3.23.1
Components of Accumulated Other Comprehensive Loss (Tables)
 3 Months Ended
Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]  
Accumulated balances for each component of AOCI
Components of AOCL:
March 31, 2023
December 31, 2022
Defined benefit plan liabilities
$(96.8)$(98.0)
Unrealized gain (loss) on financial instruments
1.7 1.7 
Other comprehensive loss before income tax effect
(95.1)(96.3)
Income tax effect(1)
2.2 2.3 
Accumulated other comprehensive loss
$(92.9)$(94.0)
(1) The allocation of the income tax effect to the components of other comprehensive loss is as follows:
March 31, 2023
December 31, 2022
Defined benefit plan liabilities$2.6 $2.6 
Unrealized loss on financial instruments(0.3)(0.3)
The following table summarizes the changes in the accumulated balances for each component of AOCL:
Defined benefit plan and other postretirement liabilitiesUnrealized gain (loss) on financial instrumentsTotal, net of tax
Balance, January 1, 2023$(95.6)$1.6 $(94.0)
Net amount reclassified to net income (loss)1.2 (0.1)1.1 
Balance, March 31, 2023
$(94.4)$1.5 $(92.9)
Balance, January 1, 2022$(84.0)$1.7 $(82.3)
Net amount reclassified to net income (loss)0.6 0.0 0.6 
Balance, March 31, 2022
$(83.4)$1.7 $(81.7)
Reclassification out of AOCI
Reclassifications out of AOCL were included in the consolidated statements of operations as follows:
Three months ended March 31,
AOCL ComponentsLocation20232022
Defined benefit plan and other postretirement liabilitiesCost of goods sold$0.8 $0.4 
Selling, general and administrative expenses0.2 0.1 
Other operating expense - net0.2 0.2 
Income tax effect— (0.1)
Net of tax$1.2 $0.6 
Unrealized loss on financial instrumentsCost of goods sold$(0.1)$0.0 
Income tax effect0.0 0.0 
Net of tax$(0.1)$0.0 
v3.23.1
Components of Net Periodic Benefit Cost (Tables)
 3 Months Ended
Mar. 31, 2023
Retirement Benefits [Abstract]  
Schedule of net periodic benefit cost
Pension Benefits
Three months ended March 31,
20232022
Service cost$1.1 $1.1 
Interest cost2.6 2.5 
Expected return on plan assets(5.9)(5.8)
Amortization of prior service costs0.0 — 
Amortization of net loss0.9 0.7 
Net periodic benefit cost (income)$(1.3)$(1.5)
Other Postretirement Benefits
Three months ended March 31,
20232022
Service cost$0.0 $0.1 
Interest cost0.7 0.7 
Amortization of prior service cost0.0 (0.5)
Amortization of net loss0.3 0.5 
Net periodic benefit cost (income)$1.0 $0.8 
v3.23.1
Derivatives (Tables)
 3 Months Ended
Mar. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]  
Derivatives not designated as hedging instruments
The following tables sets forth the Company's derivative assets and liabilities that were accounted for at fair value and not designated as cash flow hedges as of March 31, 2023 and December 31, 2022, respectively:
 Asset Fair Value
March 31, 2023December 31, 2022
Commodity contracts(1)
$52.5 $129.1 
Foreign exchange contracts(2)
0.1 — 
Total$52.6 $129.1 
 Liability Fair Value
March 31, 2023December 31, 2022
Commodity contracts(1)
$15.1 $23.7 
Foreign exchange contracts(2)
4.2 7.3 
Total$19.3 $31.0 
(1) Commodity contracts reflect our outstanding LME forward financial sales contracts, MWP forward financial sales contracts, fixed for floating swaps, Nord Pool power price swaps, and Indiana Hub power price swaps. At March 31, 2023, $7.1 million of Due to affiliates, and $5.9 million of Due to affiliates - less current portion were related to commodity contracts with Glencore. At December 31, 2022, $11.9 million of Due to affiliates, and $8.3 million of Due to affiliates - less current portion were related to commodity contract liabilities with Glencore.
(2) Foreign exchange contracts reflect our outstanding FX swaps and the casthouse currency hedges.
Schedule of derivative instruments
The following table summarizes the net loss on forward and derivative contracts:
Three months ended March 31,
20232022
Commodity contracts(1)
$(59.1)$(56.0)
Foreign exchange contracts1.6 (1.0)
   Total$(57.5)$(57.0)
(1) For the three months ended March 31, 2023, $14.9 million of the net loss was with Glencore, and for the three months ended March 31, 2022, $58.9 million of the net loss was with Glencore.
v3.23.1
Curtailment of Operations - Hawesville (Details) - Curtailment Of Operations
$ in Millions
 3 Months Ended
Mar. 31, 2023
USD ($)
Restructuring Cost and Reserve [Line Items]  
Severance costs $ 7.0
Gain (loss) on material sales 0.7
Temporary Facility Closing, Excess Capacity  
Restructuring Cost and Reserve [Line Items]  
Excess capacity charges $ 5.4
v3.23.1
Related Party Transactions - Narrative (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Dec. 09, 2022
Related Party Transaction [Line Items]      
Net sales to Glencore $ 412.2 $ 433.1  
Vlissingen facility agreement | Affiliated Entity | Vlissingen      
Related Party Transaction [Line Items]      
Credit facility face amount     $ 90.0
Stated interest rate, percentage     8.75%
Glencore | Supply Commitment      
Related Party Transaction [Line Items]      
Net sales to Glencore $ 21.0 $ 0.0  
Consolidated sales | Customer concentration risk | Glencore      
Related Party Transaction [Line Items]      
Major customer, percentage of revenue, net (percent) 75.00% 57.00%  
Glencore      
Related Party Transaction [Line Items]      
Ownership percentage by noncontrolling owners 42.90%    
Economic ownership percentage by related party 46.10%    
v3.23.1
Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Related Party Transaction [Line Items]    
Net sales to Glencore $ 412.2 $ 433.1
Glencore    
Related Party Transaction [Line Items]    
Net sales to Glencore 412.2 433.1
Purchases from Glencore $ 76.1 $ 54.5
v3.23.1
Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Disaggregation of Revenue [Line Items]    
Revenue $ 552.4 $ 753.6
UNITED STATES    
Disaggregation of Revenue [Line Items]    
Revenue 342.3 506.1
ICELAND    
Disaggregation of Revenue [Line Items]    
Revenue $ 210.1 $ 247.5
v3.23.1
Fair Value Measurements - Recurring Fair Value Measurements (Details) - Recurring - USD ($)
$ in Millions
Mar. 31, 2023
Dec. 31, 2022
ASSETS:    
Cash equivalents $ 7.2 $ 5.6
Trust assets 1.5 0.1
Derivative instruments 52.6 129.1
TOTAL 61.3 134.8
LIABILITIES:    
Derivative instruments (19.3) 31.0
TOTAL (19.3) 31.0
Level 1    
ASSETS:    
Cash equivalents 7.2 5.6
Trust assets 1.5 0.1
Derivative instruments 0.0 0.0
TOTAL 8.7 5.7
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 52.6 127.3
TOTAL 52.6 127.3
LIABILITIES:    
Derivative instruments (19.3) 26.4
TOTAL (19.3) 26.4
Level 3    
ASSETS:    
Cash equivalents 0.0 0.0
Trust assets 0.0 0.0
Derivative instruments 0.0 1.8
TOTAL 0.0 1.8
LIABILITIES:    
Derivative instruments 0.0 4.6
TOTAL $ 0.0 $ 4.6
v3.23.1
Fair Value Measurements - Significant Unobservable Inputs (Details) - Fixed to Variable London Metals Exchange Swap Net
$ in Millions
Mar. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Fair Value $ 0.0 $ (2.8)
Level 3 | Discount rate, net    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Value/Range of Unobservable Input 0.0858 0.0858
v3.23.1
Fair Value Measurements - Level 3 Reconciliation (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
LME Swap Assets    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Balance, beginning $ 1.8  
Purchases, sales, settlements    
Transfers out of Level 3 (1.8)  
Balance, ending 0.0  
Change in unrealized gains (losses) 0.0  
Nord Pool Swap    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Balance, beginning   $ 0.2
Total realized/unrealized gains (losses)    
Included in net income (loss)   0.0
Purchases, sales, settlements    
Transfers into Level 3   0.0
Transfers out of Level 3   (0.2)
Balance, ending   0.0
Change in unrealized gains (losses)   0.0
LME Swap    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Balance, beginning (4.6) (5.1)
Total realized/unrealized gains (losses)    
Included in net income (loss)   (9.1)
Purchases, sales, settlements    
Transfers into Level 3   (2.5)
Transfers out of Level 3 4.6 (0.0)
Balance, ending 0.0 (16.7)
Change in unrealized gains (losses) $ 0.0 (9.1)
FX Swap    
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]    
Balance, beginning   (0.2)
Total realized/unrealized gains (losses)    
Included in net income (loss)   0.0
Purchases, sales, settlements    
Transfers into Level 3   0.0
Transfers out of Level 3   0.2
Balance, ending   0.0
Change in unrealized gains (losses)   $ 0.0
v3.23.1
(Loss) Earnings Per Share - Schedule of EPS (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Earnings Per Share [Abstract]    
Net (loss) income $ (38.6) $ 17.7
Less: net income allocated to participating securities 0.0 1.1
Basic EPS:    
Net income (loss) allocated to common stockholders $ (38.6) $ 16.6
Net income (loss) allocated to common stockholders (in shares) 92.3 91.2
Net income (loss) allocated to common stockholders (in dollars per share) $ (0.42) $ 0.18
Share-based compensation $ 0.0 $ 0.0
Share-based compensation (in shares) 0.0 1.1
Convertible senior notes $ 0.0 $ 0.7
Convertible senior notes (in shares) 0.0 4.8
Diluted EPS:    
Net (loss) income allocated to common stockholders with assumed conversion $ (38.6) $ 17.3
Net income (loss) allocated to common stockholders with assumed conversion (in shares) 92.3 97.1
Net income (loss) allocated to common stockholders with assumed conversion (in dollars per share) $ (0.42) $ 0.18
v3.23.1
(Loss) Earnings Per Share - Securities Excluded (Details) - shares
shares in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Share-based compensation - PSU | Share-based compensation - TVPSU    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Securities excluded from calculation of diluted EPS (in shares) 0.6 0.0
Share-based compensation - PSU | Share-based compensation - PSU    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Securities excluded from calculation of diluted EPS (in shares) 0.3 0.7
Convertible preferred shares    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Securities excluded from calculation of diluted EPS (in shares) 5.4 5.9
Convertible notes    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Securities excluded from calculation of diluted EPS (in shares) 4.6 0.0
v3.23.1
Shareholders’ Equity (Details) - USD ($)
 3 Months Ended 96 Months Ended
Mar. 31, 2015
Mar. 31, 2023
Dec. 31, 2022
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)   99,510,499 99,510,499    
Common stock, shares, outstanding (in shares)   92,323,978 92,323,978    
Preferred stock, shares authorized (in shares)   5,000,000 5,000,000    
Preferred stock par value (in dollars per share)   $ 0.01 $ 0.01    
Preferred shares issued (in shares)         160,000
Number of shares issued for each share of preferred stock (in shares)   100      
Stock repurchase program, authorized amount   $ 130,000,000   $ 60,000,000  
Stock repurchase program, authorized, increase amount $ 70,000,000        
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 $ 0.01    
Preferred shares outstanding (in shares)   53,854 53,854    
v3.23.1
Income Taxes (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Income Tax Disclosure [Abstract]    
Income tax expense (benefit) $ (0.2) $ 1.7
v3.23.1
Inventories (Details) - USD ($)
$ in Millions
Mar. 31, 2023
Dec. 31, 2022
Inventory, Net [Abstract]    
Raw materials $ 98.8 $ 64.9
Work-in-process 47.8 46.0
Finished goods 43.4 58.0
Operating and other supplies 244.8 229.9
Total inventories $ 434.8 $ 398.8
v3.23.1
Debt - Activity (Details) - USD ($)
$ in Millions
Mar. 31, 2023
Dec. 31, 2022
Apr. 30, 2021
Debt Instrument [Line Items]      
Hancock County industrial revenue bonds ("IRBs") due April 1, 2028, interest payable quarterly $ 7.8 $ 7.8  
Grundartangi casthouse debt facility 59.3 49.4  
Convertible senior notes 84.5 84.4  
Total debt 518.8 527.7  
Industrial revenue bonds, variable      
Debt Instrument [Line Items]      
Hancock County industrial revenue bonds ("IRBs") due April 1, 2028, interest payable quarterly $ 7.8 7.8  
Effective interest rate, maximum 12.00%    
Stated interest rate, percentage 4.11%    
Revolving credit facility | U.S. revolving credit facility      
Debt Instrument [Line Items]      
Revolving credit facility $ 63.1 90.0  
Stated interest rate, percentage 8.75%    
Revolving credit facility | Iceland revolving line of credit      
Debt Instrument [Line Items]      
Revolving credit facility $ 45.0 35.0  
Stated interest rate, percentage 7.66%    
Casthouse facility | Iceland revolving line of credit      
Debt Instrument [Line Items]      
Secured Debt $ 59.3 49.4  
Stated interest rate, percentage 8.08%    
Financing fees $ 0.6    
Iceland term facility | Iceland revolving line of credit      
Debt Instrument [Line Items]      
Revolving credit facility 12.3 13.3  
Secured Debt $ 0.0 1.2  
Stated interest rate, percentage 5.77%    
Financing fees $ 0.0    
Senior notes | Senior secured notes, 7.5%      
Debt Instrument [Line Items]      
Grundartangi casthouse debt facility $ 246.8 246.6  
Stated interest rate, percentage 7.50%   7.50%
Financing fees $ 3.2    
Senior notes | Senior convertible notes, 2.75%      
Debt Instrument [Line Items]      
Convertible senior notes $ 84.5 $ 84.4  
Stated interest rate, percentage 2.75%    
Financing fees $ 1.8    
v3.23.1
Debt - Narrative (Details)
$ / shares in Units, € in Millions
 1 Months Ended
Apr. 30, 2021
USD ($)
$ / shares
Mar. 31, 2023
USD ($)
Sep. 20, 2022
EUR (€)
Nov. 02, 2021
USD ($)
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 debt 245,200,000      
Senior secured notes, 7.5% | Level 2 | Senior notes        
Line of Credit Facility [Line Items]        
Fair value of debt instrument   $ 237,800,000    
Convertible notes | Senior notes        
Line of Credit Facility [Line Items]        
Face amount $ 86,300,000      
Percentage of principal amount redeemed 100.00%      
Proceeds from convertible notes $ 83,700,000      
Conversion ratio 0.0533547      
Conversion price (in dollars per share) | $ / shares $ 18.74      
Convertible notes | Level 2 | Senior notes        
Line of Credit Facility [Line Items]        
Fair value of debt instrument   $ 70,700,000    
Revolving credit facility | U.S. revolving credit facility        
Line of Credit Facility [Line Items]        
Stated interest rate, percentage   8.75%    
Credit facility face amount   $ 250,000,000    
Revolving credit facility | Iceland revolving line of credit        
Line of Credit Facility [Line Items]        
Stated interest rate, percentage   7.66%    
Credit facility face amount   $ 100,000,000.0    
Medium-term Notes        
Line of Credit Facility [Line Items]        
Credit facility face amount | €     € 13.6  
Casthouse facility        
Line of Credit Facility [Line Items]        
Credit facility face amount       $ 130,000,000
Casthouse facility | Iceland revolving line of credit        
Line of Credit Facility [Line Items]        
Stated interest rate, percentage   8.08%    
Iceland term facility | Iceland revolving line of credit        
Line of Credit Facility [Line Items]        
Stated interest rate, percentage   5.77%    
Iceland term facility | Iceland revolving line of credit | EURIBOR        
Line of Credit Facility [Line Items]        
Stated interest rate, percentage   3.20%    
v3.23.1
Debt - Credit Facility (Details)
€ in Millions
Mar. 31, 2023
USD ($)
Mar. 31, 2023
EUR (€)
Dec. 31, 2022
USD ($)
Sep. 20, 2022
EUR (€)
Nov. 02, 2021
USD ($)
Casthouse facility          
Line of Credit Facility [Line Items]          
Credit facility face amount         $ 130,000,000
Medium-term Notes          
Line of Credit Facility [Line Items]          
Credit facility face amount | €       € 13.6  
Medium-term Notes | EURIBOR          
Line of Credit Facility [Line Items]          
Outstanding borrowings $ 12,300,000 € 11.3      
U.S. revolving credit facility          
Line of Credit Facility [Line Items]          
Letter of credit sub-facility amount 150,000,000        
U.S. revolving credit facility | Revolving credit facility          
Line of Credit Facility [Line Items]          
Credit facility face amount 250,000,000        
Outstanding borrowings 63,100,000        
Outstanding letters of credit issued 41,100,000        
Credit facility maximum amount 250,000,000.0        
Revolving credit facility 63,100,000   $ 90,000,000.0    
Borrowing availability 169,800,000        
Borrowing availability, net of borrowings 65,600,000        
Iceland revolving line of credit | Revolving credit facility          
Line of Credit Facility [Line Items]          
Credit facility face amount 100,000,000.0        
Outstanding borrowings 45,000,000.0        
Outstanding letters of credit issued 0        
Credit facility maximum amount 80,000,000        
Revolving credit facility 45,000,000   35,000,000.0    
Borrowing availability 100,000,000.0        
Borrowing availability, net of borrowings 55,000,000.0        
Iceland revolving line of credit | Iceland term facility          
Line of Credit Facility [Line Items]          
Revolving credit facility $ 12,300,000   $ 13,300,000    
v3.23.1
Debt - Casthouse and Surety (Details)
€ in Millions
 1 Months Ended
Nov. 02, 2021
USD ($)
Sep. 30, 2022
Nov. 30, 2021
Mar. 31, 2023
USD ($)
Dec. 09, 2022
USD ($)
Sep. 20, 2022
EUR (€)
Casthouse facility            
Debt Instrument [Line Items]            
Debt instrument, term     8 years      
Credit facility face amount $ 130,000,000          
Debt instrument, quarterly installment fee 1.739%          
Debt instrument, remaining payment after drawdown of funds 60.00%          
Medium-term notes, outstanding borrowings       $ 60,000,000    
Surety Bond            
Debt Instrument [Line Items]            
Loss contingency accrual       $ 6,600,000    
Medium-term Notes            
Debt Instrument [Line Items]            
Credit facility face amount | €           € 13.6
Medium-term Notes | EURIBOR            
Debt Instrument [Line Items]            
Debt instrument, basis spread on variable rate   3.20%        
Vlissingen facility agreement | Secured Debt | Vlissingen            
Debt Instrument [Line Items]            
Face amount         $ 90,000,000  
v3.23.1
Commitments and Contingencies (Details)
 1 Months Ended 3 Months Ended 12 Months Ended
Oct. 01, 2021
USD ($)
Apr. 01, 2021
Aug. 18, 2017
USD ($)
Sep. 30, 2017
USD ($)
Mar. 31, 2023
USD ($)
laborUnion
MW
Mar. 31, 2022
USD ($)
Dec. 31, 2013
USD ($)
Jul. 31, 2021
MW
Labor Commitments [Abstract]                
Percentage of total work force in union         58.00%      
Percentage of Grundartangi work force represented by the labor unions         87.00%      
Number of labor unions Grundartangi subsidiary entered into a new labor agreement with | laborUnion         5      
Percentage of U.S. based work force represented by a union         42.00%      
Contingent consideration, accrued interest and principal         $ 29,800,000      
PBGC                
PBGC Settlement [Abstract]                
Required pension contributions above minimum             $ 17,400,000  
Payment for pension benefits         0 $ 0    
Pension contributions, amended term, annual contribution $ 2,400,000       $ 2,400,000      
Pension contributions, amended term, total contribution $ 9,600,000              
Pension contributions, term 4 years              
Santee Cooper                
Power Contingencies [Abstract]                
Power agreement, power supply, percentage   100.00%            
Power supply agreement, increase production, at full capacity, percentage   75.00%            
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      
Power currently available under the power purchase agreement, extension (in megawatts) | MW         42     161
Power currently available under the power purchase agreement, requested (in megawatts) | MW               182
Power rate | MW         119      
Netherlands                
Labor Commitments [Abstract]                
Percentage of Vlissingen work force represented by the labor union         100.00%      
Ravenswood Retiree Medical Benefits Changes                
Ravenswood litigation [Abstract]                
Litigation settlement amount     $ 23,000,000          
Ravenswood litigation settlement installment period     10 years   9 years      
Litigation payment to trust       $ 5,000,000        
Gain (loss) related to litigation settlement       5,500,000        
Loss contingency accrual       $ 12,500,000        
Litigation settlement, amount awarded to other party, annual payments         $ 2,000,000      
Other current liabilities         2,000,000      
Other liabilities         $ 4,900,000      
v3.23.1
Components of Accumulated Other Comprehensive Loss - Components of AOCI (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Other comprehensive loss before income tax effect $ (95.1)   $ (96.3)
Defined benefit plan liabilities 2.2   2.3
Accumulated other comprehensive loss (92.9)   (94.0)
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, start 399.3 $ 421.0  
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent 1.1 0.6  
Balance, end 362.4 439.8  
Defined benefit plan liabilities      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Other comprehensive loss before income tax effect (96.8)   (98.0)
Defined benefit plan liabilities 2.6   2.6
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, start (95.6) (84.0)  
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent 1.2 0.6  
Balance, end (94.4) (83.4)  
Unrealized gain (loss) on financial instruments      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Other comprehensive loss before income tax effect 1.7   1.7
Defined benefit plan liabilities (0.3)   $ (0.3)
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, start 1.6 1.7  
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent (0.1) (0.0)  
Balance, end 1.5 1.7  
Accumulated other comprehensive loss      
AOCI Attributable to Parent, Net of Tax [Roll Forward]      
Balance, start (94.0) (82.3)  
Balance, end $ (92.9) $ (81.7)  
v3.23.1
Components of Accumulated Other Comprehensive Loss - Reclassifications out of AOCI (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]    
Cost of goods sold $ (504.3) $ (660.4)
Selling, general and administrative expenses (13.4) (11.7)
Other operating expense - net (7.2) (0.2)
Income tax effect 0.2 (1.7)
Net (loss) income (38.6) 17.7
Reclassification out of accumulated other comprehensive income | Defined benefit plan liabilities    
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]    
Cost of goods sold 0.8 0.4
Selling, general and administrative expenses 0.2 0.1
Other operating expense - net 0.2 0.2
Income tax effect 0.0 (0.1)
Net (loss) income 1.2 0.6
Reclassification out of accumulated other comprehensive income | Unrealized loss on financial instruments    
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]    
Cost of goods sold (0.1) 0.0
Income tax effect 0.0 0.0
Net (loss) income $ (0.1) $ 0.0
v3.23.1
Components of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Pension benefits    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Service cost $ 1.1 $ 1.1
Interest cost 2.6 2.5
Expected return on plan assets (5.9) (5.8)
Amortization of prior service costs 0.0 0.0
Amortization of net loss 0.9 0.7
Net periodic benefit cost (income) (1.3) (1.5)
Other postretirement benefits    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Service cost 0.0 0.1
Interest cost 0.7 0.7
Amortization of prior service costs (0.0) (0.5)
Amortization of net loss 0.3 0.5
Net periodic benefit cost (income) $ 1.0 $ 0.8
v3.23.1
Derivatives - Narrative (Details) - 3 months ended Mar. 31, 2023
€ in Millions, $ in Millions
USD ($)
MWh
t
EUR (€)
LME Swap    
Derivative [Line Items]    
Open position to offset fixed prices (in tonnes) | t 70,464  
Fixed For Floating Swaps    
Derivative [Line Items]    
Open position to offset fixed prices (in tonnes) | t 2,878  
Nordpool Power Price Swap | Grundartangi    
Derivative [Line Items]    
Derivative liability (in MwH) | MWh 745,908  
FX Swap    
Derivative [Line Items]    
Derivative asset | €   € 24.5
Indiana Hub Power Price Swaps    
Derivative [Line Items]    
Derivative liability (in MwH) | MWh 132,000  
USD ISK Forward Swap | Not designated as hedging instrument | Short    
Derivative [Line Items]    
Derivative, forward contracts | $ $ 4,346.7  
USD Euro Forward Swap | Not designated as hedging instrument | Long    
Derivative [Line Items]    
Derivative, forward contracts | $ $ 7.6  
v3.23.1
Derivatives - Assets and Liabilities (Details) - USD ($)
$ in Millions
Mar. 31, 2023
Dec. 31, 2022
Derivative [Line Items]    
Due to affiliate, current $ 22.6 $ 17.0
Due to affiliate, noncurrent 5.9 8.3
Not designated as hedging instrument    
Derivative [Line Items]    
Derivative asset 52.6 129.1
Derivative liability 19.3 31.0
Not designated as hedging instrument | Commodity contract    
Derivative [Line Items]    
Derivative asset 52.5 129.1
Derivative liability 15.1 23.7
Not designated as hedging instrument | Foreign exchange contract    
Derivative [Line Items]    
Derivative asset 0.1 0.0
Derivative liability 4.2 7.3
Glencore | Commodity contract    
Derivative [Line Items]    
Due from affiliate, current 7.1  
Due from affiliate, noncurrent $ 5.9  
Due to affiliate, current   11.9
Due to affiliate, noncurrent   $ 8.3
v3.23.1
Derivatives - Net Gain (Loss) (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Derivative [Line Items]    
Derivative, (loss) gain on derivative, net $ (57.5) $ (57.0)
Commodity contract    
Derivative [Line Items]    
Derivative, (loss) gain on derivative, net (59.1) (56.0)
Commodity contract | Glencore    
Derivative [Line Items]    
Derivative, (loss) gain on derivative, net (14.9) (58.9)
Foreign exchange contract    
Derivative [Line Items]    
Derivative, (loss) gain on derivative, net $ 1.6 $ (1.0)
v3.23.1
Subsequent Events (Details) - Subsequent Event
May 02, 2023
USD ($)
Subsequent Event [Line Items]  
Payments to acquire interest in joint venture $ 1.00
Jamalco  
Subsequent Event [Line Items]  
Ownership percentage by noncontrolling owners 55.00%
Jamalco | Clarendon Alumina Production Limited  
Subsequent Event [Line Items]  
Ownership percentage by noncontrolling owners 45.00%