Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for accounts receivable, current	$ 115	$ 125
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, issued (in shares)	683,494,944	683,494,944
Treasury stock, shares (in shares)	182,847,640	178,580,208