Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains (losses), net	$ 18	$ (82)	$ (7)
Income before income taxes	2,988	3,093	3,517
Applicable income tax expense	(639)	(647)	(747)
Net Income	2,349	2,446	2,770
Interest and fees on loans and leases	7,334	4,954	4,079
Compensation and benefits	(2,694)	(2,554)	(2,626)
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net Income	(261)	74	213
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	(1)	2	(4)
Income before income taxes	(1)	2	(4)
Applicable income tax expense	0	0	1
Net Income	(1)	2	(3)
Reclassification out of AOCI | Cash flow hedge derivatives
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	(334)	99	293
Applicable income tax expense	77	(22)	(70)
Net Income	(257)	77	223
Interest and fees on loans and leases	(334)	99	293
Reclassification out of AOCI | Net periodic benefit costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	(4)	(6)	(9)
Applicable income tax expense	1	1	2
Net Income	(3)	(5)	(7)
Reclassification out of AOCI | Amortization of net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	(2)	(3)	(6)
Reclassification out of AOCI | Settlements
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	$ (2)	$ (3)	$ (3)