Earnings Per Share - Reconciliation of the Earnings (Losses) and Number of Shares Used in Calculations of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Computation of Basic Earnings Per Share
Net income	$ 375	$ 420
Shares for basic earnings per share (in shares)	339.6	358.4
Basic earnings per share (in USD per share)	$ 1.10	$ 1.17
Computation of Diluted Earnings Per Share
Net income	$ 375	$ 420
Shares for basic earnings per share (in shares)	339.6	358.4
Effect of dilutive securities
Share-based compensation (in shares)	3.2	4.9
Shares for diluted earnings per share (in shares)	342.8	363.3
Diluted earnings per share (in USD per share)	$ 1.09	$ 1.16