Consolidated Balance Sheets Parentheticals (Parentheticals) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Allowance for doubtful accounts	$ 32	$ 31
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 8,671	$ 8,359
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	343,333,333	343,333,333
Common stock, shares issued	221,915,741	218,380,070
Common stock, shares outstanding	221,915,741	218,380,070