Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Allowance for bad debt	$ 92	$ 137
Accumulated depreciation	$ 8,056	$ 7,096
Shareholders’ equity:
Common stock, par value (in dollars per share)	$ 2.50	$ 2.50
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, shares issued (in shares)	1,073,000,000	1,073,000,000
Treasury shares (in shares)	144,000,000	152,000,000