Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 851	$ 939
Series preferred stock, par value (USD per share)	$ 0.10	$ 0.10
Series preferred stock, shares authorized	250,000,000	250,000,000
Series preferred stock, shares issued	0	0
Common stock, par value (USD per share)	$ 0.10	$ 0.10
Common stock, shares authorized	6,250,000,000	6,250,000,000
Common stock, shares issued	4,291,433,646	4,242,374,240
Treasury stock, shares issued	159,418,545	162,897,868