Bank Premises and Equipment - Summary of Bank Premises and Equipment (Details) - USD ($) $ in Millions		Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization		$ (2,963)	$ (2,889)
Total bank premises and equipment	[1]	2,053	1,995
Land and and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross		616	639
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross		1,573	1,575
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross		2,235	2,126
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross		446	432
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross		93	85
Land and improvements held for sale
Property, Plant and Equipment [Line Items]
Property and equipment, gross		28	8
Buildings held for sale
Property, Plant and Equipment [Line Items]
Property and equipment, gross		24	18
Equipment held for sale
Property, Plant and Equipment [Line Items]
Property and equipment, gross		1	1
Other property
Property, Plant and Equipment [Line Items]
Land improvements		$ 56	$ 51

[1] Includes $53 and $27 of bank premises and equipment held for sale at June 30, 2020 and December 31, 2019, respectively.