Premises, Equipment and Leases - Components of Premises and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 8,993	$ 9,188
Less: Accumulated depreciation and amortization	(4,706)	(4,810)
Total premises and equipment, net	4,287	4,378
Land
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	366	382
Buildings and improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	3,742	3,903
Furniture and equipment
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	1,973	2,218
Computer software
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	2,144	1,996
In progress
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 768	$ 689