Property and Equipment, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Cost of property and equipment	$ 1,002	$ 1,052
Less accumulated depreciation	(749)	(770)
Property and equipment, net	253	282
Depreciation expense	124	138	$ 130
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	252	248
Computer equipment
Property, Plant and Equipment [Line Items]
Cost of property and equipment	654	700
Office furniture and other equipment
Property, Plant and Equipment [Line Items]
Cost of property and equipment	$ 91	$ 99