Premises, Equipment & Lease Commitments Premises, Equipment & Lease Commitments - Components of Premises and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 8,727	$ 8,264
Less: Accumulated depreciation and amortization	(4,536)	(4,231)
Total premises and equipment, net	4,191	4,033
Land
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	386	406
Buildings and improvements
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	3,994	3,302
Furniture and equipment
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	2,018	1,901
Computer software
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	1,847	1,753
In progress
Property, Plant and Equipment [Line Items]
Total premises and equipment, gross	$ 482	$ 902