Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for accounts receivable	$ 714	$ 758
Preferred stock, par value (usd per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	5,000,000	5,000,000
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	5,600,000,000	5,600,000,000
Common stock, issued (in shares)	1,253,000,000	1,266,000,000
Common stock, outstanding (in shares)	1,253,000,000	1,266,000,000