Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Allowance for bad debts	$ 137	$ 91
Accumulated depreciation	$ 7,096	$ 6,064
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)	1,073	1,069
Treasury shares (in shares)	152	159