v3.26.1
Derivatives, Hedging Programs and Other Financial Instruments - Schedule of Fair Value of Derivative Financial Assets and Liabilities (Details) - USD ($)
Jun. 30, 2026
Dec. 31, 2025
Designated as Hedging Instrument | Purchase    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Liabilities $ (19,200,000) $ (100,000)
Not Designated as Hedging Instrument    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Net Amount 0 0
Fair Value, Measurements, Recurring    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets 7,400,000 9,600,000
Liabilities (24,600,000) (3,800,000)
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets 7,400,000 9,600,000
Liabilities (24,600,000) (3,800,000)
Net Amount (17,200,000) 5,800,000
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1 | Designated as Hedging Instrument | Purchase | Natural Gas    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets 1,000,000.0 700,000
Liabilities (2,700,000) (1,300,000)
Net Amount (1,700,000) (600,000)
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1 | Designated as Hedging Instrument | Purchase | Aluminum    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets 400,000 2,600,000
Liabilities (12,600,000)  
Net Amount (12,200,000) 2,600,000
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1 | Designated as Hedging Instrument | Purchase | Fixed Price Purchase Contracts for MWP    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets 1,600,000 3,800,000
Liabilities (6,400,000) (100,000)
Net Amount (4,800,000) 3,700,000
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1 | Designated as Hedging Instrument | Purchase | Fixed Price Sale Contracts for MWP    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Liabilities 0 (1,600,000)
Net Amount (0) (1,600,000)
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1 | Designated as Hedging Instrument | Purchase | Foreign Currency    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets   100,000
Net Amount   100,000
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1 | Designated as Hedging Instrument | Purchase | Alloying Metals    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets 2,900,000 2,400,000
Net Amount 2,900,000 2,400,000
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1 | Designated as Hedging Instrument | Purchase | Electricity    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets 1,200,000  
Liabilities (2,900,000)  
Net Amount (1,700,000)  
Fair Value, Measurements, Recurring | Cash Flow Hedges | Level 1 | Designated as Hedging Instrument | Sales | Fixed Price Sale Contracts for London Metal Exchange [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Assets 300,000  
Liabilities   (800,000)
Net Amount $ 300,000 $ (800,000)