Property and Equipment, Net (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 1,131	$ 1,110
Less: accumulated depreciation and amortization	(839)	(790)
Total property and equipment, net	292	320
Office and Computer Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 221	242
Office and Computer Equipment | Minimum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	3 years
Office and Computer Equipment | Maximum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	10 years
Office Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 51	52
Office Furniture and Fixtures | Minimum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	3 years
Office Furniture and Fixtures | Maximum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	10 years
Internal-use Computer Software
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 619	574
Internal-use Computer Software | Minimum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	1 year
Internal-use Computer Software | Maximum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	10 years
Leasehold Improvements and Building
Property, Plant and Equipment [Line Items]
Total property and equipment, at cost	$ 240	$ 242
Leasehold Improvements and Building | Minimum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	1 year
Leasehold Improvements and Building | Maximum
Property, Plant and Equipment [Line Items]
Property plant and equipment useful life	21 years