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Property, Plant and Equipment (Regulated and Non-Regulated Generation and Distribution PP&E) (Details) - USD ($)
$ in Millions
Dec. 31, 2018
Dec. 31, 2017
Property, Plant and Equipment [Line Items]    
Electric generation, distribution assets and other $ 25,242 $ 24,119
Accumulated depreciation (8,227) (7,942)
Net electric generation and distribution assets and other 17,015 16,177
Regulated Operation [Member]    
Property, Plant and Equipment [Line Items]    
Electric generation, distribution assets and other 8,959 8,093
Accumulated depreciation (3,504) (3,357)
Net electric generation and distribution assets and other 5,455 4,736
Unregulated Operation [Member]    
Property, Plant and Equipment [Line Items]    
Electric generation, distribution assets and other 16,283 16,026
Accumulated depreciation (4,723) (4,585)
Net electric generation and distribution assets and other $ 11,560 $ 11,441