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, 2020	Mar. 31, 2019
Computation of Basic Earnings Per Share
Net income	$ 31	$ 375
Shares for basic earnings per share (in shares)	325.4	339.6
Basic earnings per share (in USD per share)	$ 0.10	$ 1.10
Computation of Diluted Earnings Per Share
Net income	$ 31	$ 375
Shares for basic earnings per share (in shares)	325.4	339.6
Effect of dilutive securities
Share-based compensation (in shares)	2.0	3.2
Shares for diluted earnings per share (in shares)	327.4	342.8
Diluted earnings per share (in USD per share)	$ 0.09	$ 1.09