Accumulated Other Comprehensive Income - Reclassification Out of AOCI (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains, net	[1]	$ 62	$ 40	$ (54)
Interest and fees on loans and leases		4,424	5,051	4,078
Compensation and benefits	[1]	2,590	2,418	2,115
Income before income taxes		1,797	3,202	2,765
Applicable income tax expense		370	690	572
Net Income		1,427	2,512	2,193
Reclassification out of AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net Income		214	12	(18)
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	9	(11)
Income before income taxes		45	9	(11)
Applicable income tax expense		(11)	(2)	2
Net Income		34	7	(9)
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		237	16	(2)
Income before income taxes		237	16	(2)
Applicable income tax expense		(50)	(3)	0
Net Income		187	13	(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		(9)	(9)	(9)
Applicable income tax expense		2	1	2
Net Income		(7)	(8)	(7)
Reclassification out of AOCI | Amortization of net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits		(6)	(6)	(6)
Reclassification out of AOCI | Settlements
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Compensation and benefits		$ (3)	$ (3)	$ (3)

[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.