Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Allowances for doubtful accounts	$ 281	$ 291
Shareholders' equity:
Common stock, par value per share	$ 1.00	$ 1.00
Common stock, shares authorized	4,320,000,000	4,320,000,000
Common stock, shares issued	3,119,843,000	3,119,843,000
Treasury stock, shares	436,688,000	437,318,000