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Property, Plant and Equipment, Net (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Dec. 31, 2012
Mar. 31, 2013
Minimum [Member]
Mar. 31, 2013
Maximum [Member]
Property, Plant and Equipment [Line Items]        
Property, plant and equipment $ 24,096 $ 24,024    
Accumulated depreciation and amortization (7,338) (7,222)    
Net property, plant and equipment in service 16,758 16,802    
Construction work-in-progress 1,376 1,255    
Total property, plant and equipment, net $ 18,134 $ 18,057    
Depreciable Life     5 years 80 years