v3.26.1
Segment, Major Customer and Major Supplier Information - Income from Reportable Segments (Details) - USD ($)
$ in Millions
 3 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting [Line Items]    
Adjusted EBITDA $ 516 $ 416
Depreciation and amortization (150) (148)
Interest expense and amortization of debt issuance costs (70) (67)
Adjustment to reconcile proportional consolidation (14) (14)
Unrealized gains (losses) on change in fair value of derivative instruments, net (78) 8
Realized gains on derivative instruments not included in Adjusted EBITDA(2) 2 3
Restructuring and impairment expenses, net (19) (85)
Gain (loss) on sale or disposal of assets, net 2 (2)
Metal price lag 173 69
Start Up Cost (21) (5)
Other, net (4) (7)
Income before income tax provision 228 146
Income tax provision (benefit) (64) (50)
Net income (loss) attributable to our common shareholder 164 96
Sierre flood    
Segment Reporting [Line Items]    
Losses, net of recoveries 0 (6)
September Oswego fire losses, net of recoveries    
Segment Reporting [Line Items]    
Losses, net of recoveries (265) 0
Operating Segments    
Segment Reporting [Line Items]    
Depreciation and amortization (157) (154)
Income tax provision (benefit) (16) (34)
Operating Segments | North America    
Segment Reporting [Line Items]    
Adjusted EBITDA 111 133
Depreciation and amortization (66) (63)
Restructuring and impairment expenses, net (4) (47)
Income tax provision (benefit) 78 3
Operating Segments | Europe    
Segment Reporting [Line Items]    
Adjusted EBITDA 101 70
Depreciation and amortization (43) (44)
Restructuring and impairment expenses, net (12) (8)
Income tax provision (benefit) (22) (8)
Operating Segments | Asia    
Segment Reporting [Line Items]    
Adjusted EBITDA 121 93
Depreciation and amortization (26) (25)
Restructuring and impairment expenses, net 0 (20)
Income tax provision (benefit) (36) (7)
Operating Segments | South America    
Segment Reporting [Line Items]    
Adjusted EBITDA 186 119
Depreciation and amortization (22) (22)
Restructuring and impairment expenses, net (1) (1)
Income tax provision (benefit) (36) (22)
Eliminations and Other    
Segment Reporting [Line Items]    
Adjusted EBITDA (3) 1
Depreciation and amortization 7 6
Income tax provision (benefit) $ (48) $ (16)