CONDENSED CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 80	$ 97
Common stock - par value (in usd per share)	$ 0.001	$ 0.001
Common stock - shares authorized (in shares)	3,580,000,000	3,580,000,000
Common stock - shares outstanding (in shares)	661,000,000	684,000,000
Treasury stock - shares (in shares)	1,050,000,000	1,021,000,000