Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 28,424	$ 25,801	$ 26,957	$ 25,318
Net loss during period	524	(77)	432	(152)
Ending balance	28,876	26,196	28,876	26,196
Investment Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(187)
Net loss during period			238
Ending balance	51		51
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(151)
Net loss during period			196
Ending balance	45		45
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(115)
Net loss during period			(4)
Ending balance	(119)		(119)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(6)
Net loss during period			2
Ending balance	(4)		(4)
Accumulated Other Comprehensive Income (Loss), Net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(551)	(865)	(459)	(790)
Net loss during period			432
Ending balance	$ (27)	$ (942)	$ (27)	$ (942)