Summary of Significant Accounting Policies (Components of Fixed Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 2,444	$ 2,402
Less: accumulated depreciation and amortization	(1,562)	(1,531)
Fixed assets, net	882	871	$ 847
Furniture and equipment
Property, Plant and Equipment [Line Items]
Fixed assets, gross	776	772
Land and buildings
Property, Plant and Equipment [Line Items]
Fixed assets, gross	360	372
Leasehold and building improvements
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 1,308	$ 1,258