Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 26,957	$ 25,318	$ 17,903
Net loss during period	295	331	(663)
Ending balance	29,027	26,957	25,318
Investment Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(187)	(329)	78
Net loss during period	34	142	(407)
Ending balance	(153)	(187)	(329)
Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(151)	(249)	66
Net loss during period	50	98	(315)
Ending balance	(101)	(151)	(249)
Defined Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(115)	(202)	(267)
Net loss during period	213	87	65
Ending balance	98	(115)	(202)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6)	(10)	(4)
Net loss during period	(2)	4	(6)
Ending balance	(8)	(6)	(10)
Accumulated Other Comprehensive Income (Loss), Net
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(459)	(790)	(127)
Net loss during period	295	331	(663)
Ending balance	$ (164)	$ (459)	$ (790)