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Property, Plant and Equipment, Net (Details) - USD ($)
$ in Millions
9 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Property, Plant and Equipment [Line Items]    
Property, plant and equipment in service, net $ 63,863 $ 63,315
Construction in Progress, Gross 3,724 2,556
Property, plant and equipment, net 67,587 65,871
Regulated Operation [Member]    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment 83,046 81,836
Accumulated depreciation and amortization (25,566) (24,478)
Property, plant and equipment in service, net 57,480 57,358
Construction in Progress, Gross 3,200 2,200
Regulated Operation [Member] | Utility generation, transmission and distribution systems    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment $ 75,751 74,660
Regulated Operation [Member] | Utility generation, transmission and distribution systems | Minimum [Member]    
Property, Plant and Equipment [Line Items]    
Depreciable Life 5 years  
Regulated Operation [Member] | Utility generation, transmission and distribution systems | Maximum [Member]    
Property, Plant and Equipment [Line Items]    
Depreciable Life 80 years  
Regulated Operation [Member] | Interstate natural gas pipeline assets    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment $ 7,295 7,176
Regulated Operation [Member] | Interstate natural gas pipeline assets | Minimum [Member]    
Property, Plant and Equipment [Line Items]    
Depreciable Life 3 years  
Regulated Operation [Member] | Interstate natural gas 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 $ 8,156 7,499
Accumulated depreciation and amortization (1,773) (1,542)
Property, plant and equipment in service, net 6,383 5,957
Unregulated Operation [Member] | Independent power plants    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment $ 6,551 6,010
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 $ 1,605 $ 1,489
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