Accumulated Other Comprehensive Income - Reclassification Out of AOCI (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 on Derivatives [Line Items]
Securities gains (losses), net	$ 10	$ (7)	$ 23	$ 3
Interest on securities	461	444	1,374	1,320
Interest and fees on loans and leases	1,910	1,899	5,640	5,445
Compensation and benefits	690	629	2,099	2,036
Other noninterest expense	245	238	768	756
Income (loss) before income taxes	728	846	2,151	2,338
Applicable income tax expense	(155)	(186)	(457)	(519)
Net Income	573	660	1,694	1,819
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net Income	(108)	(72)	(300)	(187)
Reclassification out of AOCI | Available-for-sale debt securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains (losses), net	(11)	0	(17)	(1)
Income (loss) before income taxes	(11)	0	(17)	(1)
Applicable income tax expense	2	0	4	0
Net Income	(9)	0	(13)	(1)
Reclassification out of AOCI | Available-for-sale debt securities transferred to held-to-maturity securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest on securities	(33)	0	(97)	0
Income (loss) before income taxes	(33)	0	(97)	0
Applicable income tax expense	7	0	21	0
Net Income	(26)	0	(76)	0
Reclassification out of AOCI | Cash flow hedge derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest and fees on loans and leases	(91)	(94)	(270)	(240)
Income (loss) before income taxes	(91)	(94)	(270)	(240)
Applicable income tax expense	21	22	62	55
Net Income	(70)	(72)	(208)	(185)
Reclassification out of AOCI | Net periodic benefit costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	1	0	1	2
Income (loss) before income taxes	(1)	0	(1)	(1)
Applicable income tax expense	0	0	0	0
Net Income	(1)	0	(1)	(1)
Reclassification out of AOCI | Other
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other noninterest expense	(2)	0	(2)	0
Income (loss) before income taxes	(2)	0	(2)	0
Applicable income tax expense	0	0	0	0
Net Income	$ (2)	$ 0	$ (2)	$ 0