Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 229	$ 162
Less: Accumulated depreciation	$ 5,251	$ 4,367
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	750	750
Common stock, shares issued	437	432
Common stock, shares outstanding	437	432