Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 27,169	$ 25,377	$ 26,957	$ 25,318
Net loss during period	38	(220)	(92)	(75)
Ending balance	28,424	25,801	28,424	25,801
Investment Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(187)
Net loss during period			8
Ending balance	(179)		(179)
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(151)
Net loss during period			(95)
Ending balance	(246)		(246)
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(115)
Net loss during period			(3)
Ending balance	(118)		(118)
Other
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(6)
Net loss during period			(2)
Ending balance	(8)		(8)
Accumulated Other Comprehensive Income (Loss), Net
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(589)	(645)	(459)	(790)
Net loss during period			(92)
Ending balance	$ (551)	$ (865)	$ (551)	$ (865)