v3.23.1
Accumulated Other Comprehensive Income​ (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2023
Mar. 31, 2022
AOCI Attributable to Parent [Abstract]    
Balance at beginning of period $ 1,357 $ 1,559
Other comprehensive income:    
Total Other comprehensive income (loss), net of tax 10 (19)
Balance at end of period 1,397 1,561
Pension and other postretirement benefits    
AOCI Attributable to Parent [Abstract]    
Balance at beginning of period (892) (1,121)
Other comprehensive income:    
Other Comprehensive Income (Loss), before Reclassifications, before Tax (1) 55
Other Comprehensive Income (Loss) before Reclassifications, Tax (1) (12)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax (2) 43
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax 10 20
Tax expense (4) (5)
Total amount reclassified from Accumulated other comprehensive loss, net of tax 6 15
Total Other comprehensive income (loss), net of tax 4 58
Balance at end of period (888) (1,063)
Foreign currency translation    
AOCI Attributable to Parent [Abstract]    
Balance at beginning of period (51) 25
Other comprehensive income:    
Total Other comprehensive income (loss), net of tax 17 (7)
Balance at end of period (34) 18
Cash flow hedges    
AOCI Attributable to Parent [Abstract]    
Balance at beginning of period 6 (15)
Other comprehensive income:    
Other Comprehensive Income (Loss), before Reclassifications, before Tax (21) (143)
Other Comprehensive Income (Loss) before Reclassifications, Tax 5 33
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax (16) (110)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax 6 53
Tax expense (1) (13)
Total amount reclassified from Accumulated other comprehensive loss, net of tax 5 40
Total Other comprehensive income (loss), net of tax (11) (70)
Balance at end of period (5) (85)
Cash flow hedges | Aluminum Contract    
Other comprehensive income:    
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax (1) (53)
Cash flow hedges | Energy Related Derivative    
Other comprehensive income:    
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax (5) 0
Accumulated other comprehensive loss    
AOCI Attributable to Parent [Abstract]    
Balance at beginning of period (937) (1,111)
Other comprehensive income:    
Total Other comprehensive income (loss), net of tax 10 (19)
Balance at end of period $ (927) $ (1,130)