Accumulated Other Comprehensive Income (Loss) - Impact to Net Income for Items Reclassified out of Accumulated Other Comprehensive Income into Earnings (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses), net	$ (119)	$ 0	$ (153)	$ (29)
Interest income	8,086	7,754	23,835	22,244
Net interest income	4,135	4,236	12,143	13,285
Other noninterest expense	(289)	(343)	(1,061)	(1,121)
Applicable income taxes	(350)	(431)	(1,142)	(1,268)
Net income	1,722	1,524	4,659	4,597
Reclassification Out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(244)	(126)	(549)	(355)
Reclassification Out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Investment Securities Available-for- Sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses), net	(119)	0	(153)	(29)
Applicable income taxes	31	0	39	7
Net income	(88)	0	(114)	(22)
Reclassification Out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Investment Securities Transferred From Available- for-Sale to Held-to-Maturity
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	(132)	(144)	(377)	(406)
Applicable income taxes	33	37	95	103
Net income	(99)	(107)	(282)	(303)
Reclassification Out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Derivative Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net interest income	(77)	(28)	(206)	(46)
Applicable income taxes	20	8	53	12
Net income	(57)	(20)	(153)	(34)
Reclassification Out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Retirement Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other noninterest expense	0	2	0	6
Applicable income taxes	0	(1)	0	(2)
Net income	$ 0	$ 1	$ 0	$ 4