Components of Other Comprehensive Income (Loss) - Schedule of Reclassification from AOCI (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and fees on loans and leases	$ 975		$ 877		$ 1,927	$ 1,683
Income tax expense	56		96		113	171
Other expense	45		52		84	96
Amounts reclassified from AOCI	(204)	$ (197)	(329)	$ (255)	(401)	(585)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI	15		15		30	28
Reclassification out of Accumulated Other Comprehensive Income | Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and fees on loans and leases	17		17		34	32
Income tax expense	(4)		(4)		(8)	(8)
Amounts reclassified from AOCI	13		13		26	24
Reclassification out of Accumulated Other Comprehensive Income | Pension and Post-retirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax expense	(1)		0		(2)	(1)
Other expense	3		2		6	5
Amounts reclassified from AOCI	$ 2		$ 2		$ 4	$ 4