Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 29,027	$ 26,957
Net loss during period	254	(130)
Ending balance	28,991	27,169
Investment Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(153)
Net loss during period	147
Ending balance	(6)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(101)
Net loss during period	108
Ending balance	7
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	98
Net loss during period	(2)
Ending balance	96
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(8)
Net loss during period	1
Ending balance	(7)
Accumulated Other Comprehensive Income (Loss), Net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(164)	(459)
Net loss during period	254
Ending balance	$ 90	$ (589)