Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Allowance for doubtful accounts	$ 25	$ 8
Equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	100,000,000	100,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	1,500,000,000	1,500,000,000
Common stock, issued (in shares)	628,000,000	607,000,000
Common stock, outstanding (in shares)	561,000,000	554,000,000
Treasury stock (in shares)	67,000,000	53,000,000