Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains, net	$ 3	$ 7	$ 13	$ 11
Interest on securities	458	437	913	876
Interest and fees on loans and leases	1,871	1,831	3,731	3,545
Income (loss) before income taxes	764	775	1,424	1,493
Applicable income tax expense	(163)	(174)	(302)	(334)
Net Income	601	601	1,122	1,159
Compensation and benefits	(656)	(650)	(1,409)	(1,407)
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net Income	(97)	(64)	(193)	(114)
Reclassification out of AOCI | Available-for-sale debt securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains, net	(4)	0	(7)	0
Income (loss) before income taxes	(4)	0	(7)	0
Applicable income tax expense	1	0	2	0
Net Income	(3)	0	(5)	0
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	(32)	0	(64)	0
Income (loss) before income taxes	(32)	0	(64)	0
Applicable income tax expense	7	0	14	0
Net Income	(25)	0	(50)	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	(90)	(81)	(179)	(146)
Income (loss) before income taxes	(90)	(81)	(179)	(146)
Applicable income tax expense	21	18	41	33
Net Income	(69)	(63)	(138)	(113)
Reclassification out of AOCI | Net periodic benefit costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income (loss) before income taxes	0	(1)	0	(1)
Applicable income tax expense	0	0	0	0
Net Income	0	(1)	0	(1)
Compensation and benefits	$ 0	$ (1)	$ 0	$ (1)