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, net	$ 55,971	$ 54,054
Construction work-in-progress	4,160	5,194
Property, plant and equipment, net	60,131	59,248
Regulated assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	73,805	71,305
Accumulated depreciation and amortization	(22,666)	(21,447)
Property, plant and equipment in service, net	51,139	49,858
Construction work-in-progress	3,900	4,300
Regulated assets [Member] | Utility generation, distribution and transmission system
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 67,044	64,645
Regulated assets [Member] | Utility generation, distribution and transmission system | Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	5 years
Regulated assets [Member] | Utility generation, distribution and transmission system | Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	80 years
Regulated assets [Member] | Interstate pipeline assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 6,761	6,660
Regulated assets [Member] | Interstate pipeline assets | Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	3 years
Regulated assets [Member] | Interstate pipeline assets | Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	80 years
Unregulated operation [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 5,574	5,035
Accumulated depreciation and amortization	(742)	(839)
Property, plant and equipment in service, net	4,832	4,196
Unregulated operation [Member] | Independent power plants
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 4,737	4,362
Unregulated operation [Member] | Independent power plants | Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	5 years
Unregulated operation [Member] | Independent power plants | Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	30 years
Unregulated operation [Member] | Other assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 837	$ 673
Unregulated operation [Member] | Other assets | Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	3 years
Unregulated operation [Member] | Other assets | Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	30 years