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, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses), net	$ (7)	$ (119)	$ (64)	$ (153)
Interest income	7,927	8,086	23,047	23,835
Net interest income	4,222	4,135	12,365	12,143
Other noninterest expense	(359)	(289)	(1,064)	(1,061)
Applicable income taxes	(524)	(350)	(1,439)	(1,142)
Net income	2,008	1,722	5,545	4,659
Reclassification Out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(145)	(244)	(453)	(549)
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	(7)	(119)	(64)	(153)
Applicable income taxes	2	31	16	39
Net income	(5)	(88)	(48)	(114)
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	(124)	(132)	(358)	(377)
Applicable income taxes	32	33	93	95
Net income	(92)	(99)	(265)	(282)
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	(65)	(77)	(191)	(206)
Applicable income taxes	16	20	48	53
Net income	(49)	(57)	(143)	(153)
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	1	0	4	0
Applicable income taxes	0	0	(1)	0
Net income	$ 1	$ 0	$ 3	$ 0