Summary of Significant Accounting Policies (Components of Fixed Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 2,436	$ 3,015
Less-accumulated depreciation and amortization	(1,589)	(2,159)
Fixed assets, net	847	856	$ 858
Furniture and equipment
Property, Plant and Equipment [Line Items]
Fixed assets, gross	811	1,326
Land and buildings
Property, Plant and Equipment [Line Items]
Fixed assets, gross	385	379
Leasehold and building improvements
Property, Plant and Equipment [Line Items]
Fixed assets, gross	$ 1,240	$ 1,310