Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains (losses), net	$ 10	$ 21	$ 13	$ (3)
Interest and fees on loans and leases	1,035	1,115	2,064	2,350
Compensation and benefits	638	627	1,343	1,274
Income before income taxes	911	244	1,794	304
Applicable income tax expense	(202)	(49)	(391)	(61)
Net income	709	195	1,403	243
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income	61	48	105	72
Reclassification out of AOCI | Net unrealized gains on available-for-sale debt securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains (losses), net	7	0	(9)	0
Income before income taxes	7	0	(9)	0
Applicable income tax expense	(2)	0	2	0
Net income	5	0	(7)	0
Reclassification out of AOCI | Net unrealized gains on cash flow hedge
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest and fees on loans and leases	73	62	146	94
Income before income taxes	73	62	146	94
Applicable income tax expense	(15)	(13)	(31)	(20)
Net income	58	49	115	74
Reclassification out of AOCI | Net periodic benefit costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	(2)	(1)	(3)	(3)
Income before income taxes	(3)	(1)	(4)	(3)
Applicable income tax expense	1	0	1	1
Net income	(2)	(1)	(3)	(2)
Reclassification out of AOCI | Settlements
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits	$ (1)	$ 0	$ (1)	$ 0