v3.23.2
Contingencies and Commitments​ (Details)
$ in Millions
 1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended 37 Months Ended
Jun. 06, 2019
plaintiff
Sep. 15, 2017
executive
Jul. 31, 2023
USD ($)
Jul. 31, 2022
USD ($)
Jun. 30, 2023
USD ($)
Mar. 31, 2023
USD ($)
Jun. 30, 2023
USD ($)
Dec. 31, 2022
USD ($)
Jun. 30, 2023
USD ($)
claimant
Jun. 30, 2023
USD ($)
claimant
Site Contingency [Line Items]                    
Environmental remediation         $ 72.0   $ 72.0 $ 85.0 $ 72.0 $ 72.0
Environmental remediation, current         34.0   34.0 40.0 $ 34.0 $ 34.0
Environmental remediation, payments         4.0   14.0      
Behrens v. Arconic                    
Loss Contingencies [Line Items]                    
Number of plaintiffs | plaintiff 247                  
Sullivan v. Arconic                    
Loss Contingencies [Line Items]                    
Number of former executives | executive   3                
Damage from Fire, Explosion or Other Hazard | Grenfell Tower Fire, Survivors And Estates Of Decedents                    
Loss Contingencies [Line Items]                    
Number of plaintiffs | claimant                   1,000
Loss Contingency, Receivable, Additions               53.0    
Loss Contingency Accrual, Payments           $ 43.0        
Loss Contingency, Receivable, Proceeds           $ 41.0        
Damage from Fire, Explosion or Other Hazard | Grenfell Tower Fire, Survivors And Estates Of Decedents | Subsequent events                    
Loss Contingencies [Line Items]                    
Loss Contingency Accrual, Payments     $ 8.0              
Damage from Fire, Explosion or Other Hazard | Grenfell Tower Fire, Survivors And Estates Of Decedents | Other Current Liabilities                    
Loss Contingencies [Line Items]                    
Loss Contingency Accrual, Provision               61.0    
Loss Contingency Accrual               61.0    
Damage from Fire, Explosion or Other Hazard | Grenfell Tower Fire, Survivors And Estates Of Decedents | Prepaid Expenses and Other Current Assets                    
Loss Contingencies [Line Items]                    
Loss Contingency, Receivable               53.0    
Damage from Fire, Explosion or Other Hazard | Grenfell Tower Fire, Emergency Responders                    
Loss Contingencies [Line Items]                    
Number of plaintiffs | claimant                 150  
Damage from Fire, Explosion or Other Hazard | Sullivan v. Arconic                    
Loss Contingencies [Line Items]                    
Loss Contingency Accrual, Provision             74.0      
Loss Contingency, Receivable, Additions             74.0      
Damage from Fire, Explosion or Other Hazard | Sullivan v. Arconic | Other Current Liabilities                    
Loss Contingencies [Line Items]                    
Loss Contingency Accrual         74.0   74.0   $ 74.0 $ 74.0
Damage from Fire, Explosion or Other Hazard | Sullivan v. Arconic | Prepaid Expenses and Other Current Assets                    
Loss Contingencies [Line Items]                    
Loss Contingency, Receivable         74.0   74.0   74.0 74.0
Massena West, NY                    
Site Contingency [Line Items]                    
Environmental remediation         30.0   30.0 38.0 30.0 30.0
Massena West, NY | Environmental Issue [Member]                    
Site Contingency [Line Items]                    
Environmental remediation, additions               (13.0)    
Massena West, NY | Environmental Issue [Member] | Scenario, Plan                    
Site Contingency [Line Items]                    
Accrual for Environmental Loss Contingencies, Revision in Estimates       $ 22.0            
Active Remediation Systems and Monitoring And Inspection Programs At Several Sites                    
Site Contingency [Line Items]                    
Accrual for Environmental Loss Contingencies, Revision in Estimates             1.0      
Second Largest Reserve                    
Site Contingency [Line Items]                    
Environmental remediation         $ 6.0   $ 6.0   $ 6.0 $ 6.0
Davenport, IA                    
Site Contingency [Line Items]                    
Environmental remediation, additions               (0.5)    
Davenport, IA | Minimum                    
Site Contingency [Line Items]                    
Estimated Future Capital Expenditures               25.0    
Davenport, IA | Maximum                    
Site Contingency [Line Items]                    
Estimated Future Capital Expenditures               $ 30.0