Bank Premises and Equipment - Summary of Bank Premises and Equipment (Details) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization		$ (3,012)	$ (2,889)
Total bank premises and equipment	[1]	2,090	1,995
Land and and improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross		626	639
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment, gross		1,587	1,575
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross		2,254	2,126
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross		450	432
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross		140	85
Land and improvements held for sale
Property, Plant and Equipment [Line Items]
Property and equipment, gross		27	8
Buildings held for sale
Property, Plant and Equipment [Line Items]
Property and equipment, gross		17	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		$ 54	$ 51

[1] Includes $45 and $27 of bank premises and equipment held for sale at September 30, 2020 and December 31, 2019, respectively.