v3.23.1
Contingencies and Commitments​ (Details)
$ in Millions
 1 Months Ended 3 Months Ended 12 Months Ended 34 Months Ended
Jun. 06, 2019
plaintiff
Sep. 15, 2017
executive
Jul. 31, 2022
USD ($)
Mar. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Mar. 31, 2023
USD ($)
claimant
Mar. 31, 2023
USD ($)
claimant
Site Contingency [Line Items]              
Environmental remediation       $ 76.0 $ 85.0 $ 76.0 $ 76.0
Environmental remediation, current       36.0 40.0 $ 36.0 $ 36.0
Environmental remediation, payments       10.0      
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 | 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
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
Massena West, NY              
Site Contingency [Line Items]              
Environmental remediation       31.0 38.0 31.0 31.0
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
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