Components of Other Comprehensive Income (Loss) - Schedule of Reclassification from AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and fees on loans and leases	$ 507	$ 327
All other expense	106	48
Income tax expense	71	5
Amounts reclassified from AOCI	(236)	(16)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI	3	2
Reclassification out of Accumulated Other Comprehensive Income | Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and fees on loans and leases	2	0
Income tax expense	(1)	0
Amounts reclassified from AOCI	1	0
Reclassification out of Accumulated Other Comprehensive Income | Pension and Post-retirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
All other expense	4	3
Income tax expense	(2)	(1)
Amounts reclassified from AOCI	$ 2	$ 2