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UTILITY PLANT AND JOINTLY-OWNED FACILITIES (Utility Plant in Service by Major Class) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Public Utility, Property, Plant and Equipment [Line Items]      
Average Annual Depreciation Rates 3.01% 3.24% 3.30%
Total Plant in Service $ 8,035 $ 7,814  
Plant acquisition adjustments $ (206) (206)  
Smaller Application Software | Minimum      
Public Utility, Property, Plant and Equipment [Line Items]      
Amortization period 3 years    
Smaller Application Software | Maximum      
Public Utility, Property, Plant and Equipment [Line Items]      
Amortization period 5 years    
Large Enterprise Software      
Public Utility, Property, Plant and Equipment [Line Items]      
Amortization period 10 years    
Generation Plant      
Public Utility, Property, Plant and Equipment [Line Items]      
Average Annual Depreciation Rates 3.05%    
Average Remaining Life in Years 22 years    
Total Plant in Service $ 3,536 3,491  
Distribution Plant      
Public Utility, Property, Plant and Equipment [Line Items]      
Average Annual Depreciation Rates 2.61%    
Average Remaining Life in Years 46 years    
Total Plant in Service $ 2,279 2,149  
Transmission Plant      
Public Utility, Property, Plant and Equipment [Line Items]      
Average Annual Depreciation Rates 1.69%    
Average Remaining Life in Years 33 years    
Total Plant in Service $ 1,323 1,295  
General Plant      
Public Utility, Property, Plant and Equipment [Line Items]      
Average Annual Depreciation Rates 6.13%    
Average Remaining Life in Years 9 years    
Total Plant in Service $ 685 653  
Intangible Plant, Software Costs and Other      
Public Utility, Property, Plant and Equipment [Line Items]      
Average Remaining Life in Years 3 years    
Total Plant in Service $ 201 224  
Plant acquisition adjustments (4) (4)  
Plant Held for Future Use      
Public Utility, Property, Plant and Equipment [Line Items]      
Total Plant in Service $ 11 $ 2