Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 26,957	$ 25,318
Net loss during period	(130)	145
Ending balance	27,169	25,377
Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(187)
Net loss during period	(10)
Ending balance	(197)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(151)
Net loss during period	(117)
Ending balance	(268)
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(115)
Net loss during period	(1)
Ending balance	(116)
Accumulated Other Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(6)
Net loss during period	(2)
Ending balance	(8)
Accumulated Other Comprehensive Income (Loss), Net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(459)	(790)
Net loss during period	(130)
Ending balance	$ (589)	$ (645)