Premises and Equipment - Premises and Equipment and Estimated Useful Lives (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Premises and Equipment, Net, by Type
Property, plant, and equipment and finance lease right-of-use asset, before accumulated depreciation and amortization	$ 834	$ 811
Less: accumulated depreciation	(442)	(395)
Premises and equipment, net	$ 392	416
Minimum
Premises and Equipment, Net, by Type
Estimated useful lives	3 years
Maximum
Premises and Equipment, Net, by Type
Estimated useful lives	30 years
Land
Premises and Equipment, Net, by Type
Premises and equipment, gross	$ 68	73
Computer hardware and software
Premises and Equipment, Net, by Type
Premises and equipment, gross	$ 410	372
Computer hardware and software \| Minimum
Premises and Equipment, Net, by Type
Estimated useful lives	3 years
Computer hardware and software \| Maximum
Premises and Equipment, Net, by Type
Estimated useful lives	7 years
Office buildings and improvements
Premises and Equipment, Net, by Type
Premises and equipment, gross	$ 195	191
Office buildings and improvements \| Minimum
Premises and Equipment, Net, by Type
Estimated useful lives	15 years
Office buildings and improvements \| Maximum
Premises and Equipment, Net, by Type
Estimated useful lives	31 years 6 months
Furniture, fixtures and equipment
Premises and Equipment, Net, by Type
Premises and equipment, gross	$ 66	68
Furniture, fixtures and equipment \| Minimum
Premises and Equipment, Net, by Type
Estimated useful lives	5 years
Furniture, fixtures and equipment \| Maximum
Premises and Equipment, Net, by Type
Estimated useful lives	7 years
Leased equipment
Premises and Equipment, Net, by Type
Premises and equipment, gross	$ 19	36
Leased equipment \| Minimum
Premises and Equipment, Net, by Type
Estimated useful lives	3 years
Leased equipment \| Maximum
Premises and Equipment, Net, by Type
Estimated useful lives	10 years
Leasehold improvements
Premises and Equipment, Net, by Type
Premises and equipment, gross	$ 10	9
Fixed assets in progress
Premises and Equipment, Net, by Type
Premises and equipment, gross	43	40
Right-of-use asset
Premises and Equipment, Net, by Type
Premises and equipment, gross	$ 23	$ 22
Leasehold improvements \| Minimum
Premises and Equipment, Net, by Type
Estimated useful lives	5 years
Leasehold improvements \| Maximum
Premises and Equipment, Net, by Type
Estimated useful lives	10 years

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount, before accumulated depreciation and amortization, of property, plant, and equipment and finance lease right-of-use asset.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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