Comprehensive Income - Accumulated Other Comprehensive Income (Loss), Net (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 25,318	$ 17,903	$ 16,187
Net gain (loss) during period	331	(663)	(65)
Ending balance	26,957	25,318	17,903
Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(329)	78	145
Net gain (loss) during period	142	(407)	(67)
Ending balance	(187)	(329)	78
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(202)	(267)	(481)
Net gain (loss) during period	87	65	214
Ending balance	(115)	(202)	(267)
Cash Flow Hedges and Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(259)	62	274
Net gain (loss) during period	102	(321)	(212)
Ending balance	(157)	(259)	62
Accumulated Other Comprehensive Income (Loss), Net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(790)	(127)	(62)
Net gain (loss) during period	331	(663)	(65)
Ending balance	$ (459)	$ (790)	$ (127)