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
	Mar. 31, 2024	Mar. 31, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains (losses), net	$ 2	$ (32)
Interest income	7,764	6,964
Net interest income	3,985	4,634
Other noninterest expense	(418)	(425)
Applicable income taxes	(347)	(455)
Net income (loss)	1,326	1,704
Reclassification Out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(120)	(118)
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	2	(32)
Applicable income taxes	(1)	8
Net income (loss)	1	(24)
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	(114)	(121)
Applicable income taxes	29	31
Net income (loss)	(85)	(90)
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	(49)	(7)
Applicable income taxes	13	1
Net income (loss)	(36)	(6)
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
Applicable income taxes	0	0
Net income (loss)	$ 0	$ 2