v3.25.2
Comprehensive income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance $ 28,991 $ 27,169 $ 29,027 $ 26,957
Total other comprehensive income (loss) 125 38 379 (92)
Ending balance 28,525 28,424 28,525 28,424
Investment Securities        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance     (153)  
Total other comprehensive income (loss)     214  
Ending balance 61   61  
Cash Flow Hedges        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance     (101)  
Total other comprehensive income (loss)     164  
Ending balance 63   63  
Defined Benefit Plans        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance     98  
Total other comprehensive income (loss)     (3)  
Ending balance 95   95  
Other        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance     (8)  
Total other comprehensive income (loss)     4  
Ending balance (4)   (4)  
Accumulated Other Comprehensive Income (Loss), Net        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 90 (589) (164) (459)
Total other comprehensive income (loss)     379 (92)
Ending balance $ 215 $ (551) $ 215 $ (551)