v3.26.1
Comprehensive income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]    
Beginning balance $ 29,177 $ 29,027
Total other comprehensive income (loss) (211) 254
Ending balance 27,972 28,991
Investment Securities    
AOCI Attributable to Parent, Net of Tax [Roll Forward]    
Beginning balance 155 (153)
Total other comprehensive income (loss) (149) 147
Ending balance 6 (6)
Cash Flow Hedges    
AOCI Attributable to Parent, Net of Tax [Roll Forward]    
Beginning balance 67 (101)
Total other comprehensive income (loss) (60) 108
Ending balance 7 7
Defined Benefit Plans    
AOCI Attributable to Parent, Net of Tax [Roll Forward]    
Beginning balance 61 98
Total other comprehensive income (loss) (1) (2)
Ending balance 60 96
Other    
AOCI Attributable to Parent, Net of Tax [Roll Forward]    
Beginning balance (6) (8)
Total other comprehensive income (loss) (1) 1
Ending balance (7) (7)
Accumulated Other Comprehensive Income (Loss), Net    
AOCI Attributable to Parent, Net of Tax [Roll Forward]    
Beginning balance 277 (164)
Total other comprehensive income (loss) (211) 254
Ending balance $ 66 $ 90