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Debt - Activity (Details) - USD ($)
Dec. 31, 2023
Dec. 31, 2022
Apr. 14, 2021
Apr. 09, 2021
Debt Instrument [Line Items]        
Total $ 479,200,000 $ 527,700,000    
Industrial Revenue Bonds, Variable        
Debt Instrument [Line Items]        
Maximum variable interest rate 12.00%      
Industrial revenue bonds due 2028        
Debt Instrument [Line Items]        
Hancock County industrial revenue bonds ("IRBs") due April 2028, interest payable quarterly (variable interest rates (not to exceed 12%)) $ 7,800,000 7,800,000    
Stated interest rate 4.00%      
Senior Notes | Senior Secured Notes, 7.5%        
Debt Instrument [Line Items]        
Financing fees $ 2,600,000      
Stated interest rate 7.50%   7.50%  
7.5% senior secured notes due April 1, 2028, net of financing fees of $2.6 million at December 31, 2023, interest payable semiannually $ 247,400,000 246,600,000    
Senior Notes | Senior Convertible Notes, 2.75%        
Debt Instrument [Line Items]        
Financing fees 1,500,000      
Stated interest rate       2.75%
2.75% convertible senior notes due May 1, 2028, net of financing fees of $1.5 million at December 31, 2023, interest payable semiannually 84,700,000 84,400,000    
U.S revolving credit facility | Revolving Credit Facility        
Debt Instrument [Line Items]        
Revolving credit facility $ 23,700,000 90,000,000.0    
Stated interest rate 9.25%      
Foreign line of credit | Revolving Credit Facility        
Debt Instrument [Line Items]        
Revolving credit facility $ 0 35,000,000.0    
Foreign line of credit | Casthouse Facility        
Debt Instrument [Line Items]        
Revolving credit facility 5,500,000 0    
Financing fees 700,000      
Secured debt $ 98,800,000 49,400,000    
Stated interest rate 8.86%      
Foreign line of credit | Iceland Term Facility        
Debt Instrument [Line Items]        
Revolving credit facility $ 1,300,000 13,300,000    
Financing fees 0      
Secured debt $ 0 1,200,000    
Stated interest rate 3.20%      
Effective interest rate (percent) 7.05%      
Foreign line of credit | Vlissingen Facility Agreement        
Debt Instrument [Line Items]        
Revolving credit facility $ 10,000,000.0 $ 0    
Secured debt $ 10,000,000.0      
Stated interest rate 8.75%