Description of Business, Basis of Presentation and Significant Accounting Policies - Activities Relating to Capitalized Software (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement in Capitalized Computer Software, Net [Roll Forward]
Beginning balance at January 1	$ 72
Amortization	(33)	$ (49)	$ (71)
Ending balance at December 31	36	72
Internal-Use Software
Movement in Capitalized Computer Software, Net [Roll Forward]
Beginning balance at January 1	15	16	13
Capitalized	5	6	9
Amortization	(7)	(7)	(6)
Ending balance at December 31	13	15	16
External-Use Software
Movement in Capitalized Computer Software, Net [Roll Forward]
Beginning balance at January 1	57	105	174
Capitalized	0	0	0
Amortization	(34)	(48)	(69)
Ending balance at December 31	$ 23	$ 57	$ 105