Consolidated Balance Sheets (Parenthetical) - USD ($) shares in Millions, $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Allowance for bad debt	$ 738	$ 725
Accumulated depreciation	$ 13,182	$ 12,249
Shareholders’ equity:
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	2,000	2,000
Common stock, shares issued (in shares)	1,069	1,069
Treasury shares (in shares)	198	196