Equipment, Office Facilities, and Property (Schedule of Equipment, Office Facilities, and Property) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		$ 5,550	$ 4,364
Accumulated depreciation and amortization		(2,667)	(2,236)
Property, Plant and Equipment, Net, Total	[1]	2,883	2,128
Software [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		2,314	1,876
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		1,444	1,056
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		455	360
Information technology equipment [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		374	253
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		325	324
Furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		288	241
Land [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		208	163
Telecommunications equipment [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		135	91
Other assets [Member]
Property, Plant and Equipment [Line Items]
Total equipment, office facilities, and property		$ 7	$ 0

[1] Certain prior year amounts have been reclassified to conform to the current year presentation. See Note 1 for additional information.