Property and Equipment, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Cost of property and equipment	$ 1,025	$ 1,050
Less accumulated depreciation	(856)	(841)
Property and equipment, net	169	209
Depreciation expense	105	117	$ 124
Land
Property, Plant and Equipment [Line Items]
Cost of property and equipment	1	1
Buildings
Property, Plant and Equipment [Line Items]
Cost of property and equipment	4	4
Leasehold improvements
Property, Plant and Equipment [Line Items]
Cost of property and equipment	227	246
Computer equipment
Property, Plant and Equipment [Line Items]
Cost of property and equipment	703	704
Office furniture and other equipment
Property, Plant and Equipment [Line Items]
Cost of property and equipment	$ 90	$ 95