Property, Plant and Equipment, Net (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment in service, net	$ 61,476	$ 60,411
Construction in Progress, Gross	3,503	2,098
Property, plant and equipment, net	64,979	62,509
Regulated assets [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	80,129	78,478
Accumulated depreciation and amortization	(24,525)	(23,603)
Property, plant and equipment in service, net	55,604	54,875
Construction in Progress, Gross	3,100	1,800
Regulated assets [Member] | Utility generation, transmission and distribution systems
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 73,138	71,536
Regulated assets [Member] | Utility generation, transmission and distribution systems | Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	5 years
Regulated assets [Member] | Utility generation, transmission and distribution systems | Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	80 years
Regulated assets [Member] | Interstate natural gas pipeline assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 6,991	6,942
Regulated assets [Member] | Interstate natural gas pipeline assets | Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	3 years
Regulated assets [Member] | Interstate natural gas pipeline assets | Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	80 years
Unregulated asset [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 7,176	6,596
Accumulated depreciation and amortization	(1,304)	(1,060)
Property, plant and equipment in service, net	5,872	5,536
Unregulated asset [Member] | Independent power plants
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 5,911	5,594
Unregulated asset [Member] | Independent power plants | Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	5 years
Unregulated asset [Member] | Independent power plants | Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	30 years
Unregulated asset [Member] | Other assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,265	$ 1,002
Unregulated asset [Member] | Other assets | Minimum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	3 years
Unregulated asset [Member] | Other assets | Maximum [Member]
Property, Plant and Equipment [Line Items]
Depreciable Life	30 years