Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains, net	[1]	$ 51	$ 5	$ 48	$ 30
Interest and fees on loans and leases		1,047	1,320	3,397	3,799
Compensation and benefits	[1]	637	584	1,911	1,843
Income before income taxes		746	689	1,051	2,261
Applicable income tax expense		165	140	228	483
Net income		581	549	823	1,778
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income		87	5	159	1
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, net		45	3	45	3
Income before income taxes		45	3	45	3
Applicable income tax expense		(11)	(1)	(11)	(1)
Net income		34	2	34	2
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		72	5	165	2
Income before income taxes		72	5	165	2
Applicable income tax expense		(16)	(1)	(35)	0
Net income		56	4	130	2
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)	(1)	(7)	(4)
Applicable income tax expense		1	0	2	1
Net income		(3)	(1)	(5)	(3)
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)	(1)	(5)	(4)
Reclassification out of AOCI | Settlements
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits		$ (2)	$ 0	$ (2)	$ 0

[1] During the first quarter of 2020, certain noninterest income and noninterest expense line items were reclassified to better align disclosures to business activities. These reclassifications were retrospectively applied to all prior periods presented. Total noninterest income and noninterest expense did not change as a result of these reclassifications.