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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Computation of Basic Earnings Per Share
Net income (loss)	$ 422	$ (11)	$ (234)	$ 31	$ 411	$ (203)
Shares for basic earnings per share (in shares)	327.1		325.6		326.9	325.5
Basic earnings (loss) per share (in USD per share)	$ 1.29		$ (0.72)		$ 1.26	$ (0.63)
Computation of Diluted Earnings Per Share
Net income (loss)	$ 422	$ (11)	$ (234)	$ 31	$ 411	$ (203)
Shares for basic earnings per share (in shares)	327.1		325.6		326.9	325.5
Effect of dilutive securities
Stock-based compensation (in shares)	2.0		0.0		2.1	0.0
Shares for diluted earnings per share (in shares)	329.1		325.6		329.0	325.5
Diluted earnings (loss) per share (in USD per share)	$ 1.28		$ (0.72)		$ 1.25	$ (0.63)
Antidilutive shares (in shares)			0.8			1.4