Share-based Compensation - Share-based Compensation Activity (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense before income taxes	$ 85	$ 72	$ 86
Income tax benefit on share-based compensation expense		0	1
Restricted Stock
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense before income taxes	53	40	56
Stock Options
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense before income taxes	10	10	9
Performance Share Units
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense before income taxes	$ 22	$ 22	$ 21