Equipment, Office Facilities, and Property (Schedule of Equipment, Office Facilities, and Property) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	$ 3,234	$ 2,932
Accumulated depreciation and amortization	(1,935)	(1,787)
Total equipment, office facilities, and property - net	1,299	1,145	[1]
Software [Member]
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	1,335	1,183
Buildings [Member]
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	807	771
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	342	322
Information technology equipment [Member]
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	299	273
Furniture and equipment [Member]
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	190	177
Telecommunications equipment [Member]
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	67	78
Construction in progress [Member]
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	26	18
Land [Member]
Property Plant And Equipment [Line Items]
Total equipment, office facilities, and property	$ 168	$ 110

[1] Adjusted for the retrospective adoption of ASU 2015-03. See New Accounting Standards in Note 2 for additional information.