Property, Plant and Equipment, Net (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment in-service	$ 26,593	$ 25,813
Accumulated depreciation and amortization	(8,410)	(8,026)
Net property, plant and equipment in-service	18,183	17,787
Construction work-in-progress	762	932
Total property, plant and equipment, net	$ 18,945	$ 18,719
Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	5 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	75 years