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Commitments and Contingencies (Details)
 1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Apr. 01, 2021
Aug. 18, 2017
USD ($)
Oct. 31, 2021
USD ($)
Sep. 30, 2017
USD ($)
Jun. 30, 2023
USD ($)
laborUnion
MW
Jun. 30, 2022
USD ($)
Jun. 30, 2023
USD ($)
laborUnion
MW
Dec. 31, 2013
USD ($)
Sep. 30, 2022
MW
Jul. 31, 2021
MW
Labor Commitments [Abstract]                    
Percentage of total work force in union         53.00%   53.00%      
Percentage of Grundartangi work force represented by the labor unions         87.00%   87.00%      
Number of labor unions Grundartangi subsidiary entered into a new labor agreement with | laborUnion         5   5      
Percentage of domestic based work force represented by a union         41.00%   41.00%      
Percentage of foreign work force, represented by the union         0.38   0.38      
Contingent consideration, accrued interest and principal         $ 30,200,000   $ 30,200,000      
Netherlands                    
Labor Commitments [Abstract]                    
Percentage of Vlissingen work force represented by the labor union         100.00%   100.00%      
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   $ 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   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  
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   2,000,000      
Other liabilities         $ 5,000,000   $ 5,000,000