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PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Schedule of Average Remaining Useful Lives of Depreciable Assets (Details)
 12 Months Ended
Dec. 31, 2023
Property, Plant and Equipment [Line Items]  
Distribution - Electric 34 years
Distribution - Natural Gas 35 years 8 months 12 days
Transmission - Electric 40 years 7 months 6 days
Distribution - Water 40 years
Solar 22 years 9 months 18 days
Other 10 years 4 months 24 days
Computer Software, Hardware and Equipment | Minimum  
Property, Plant and Equipment [Line Items]  
Estimated useful life of property, plant and equipment (in years) 5 years
Computer Software, Hardware and Equipment | Maximum  
Property, Plant and Equipment [Line Items]  
Estimated useful life of property, plant and equipment (in years) 15 years
Buildings  
Property, Plant and Equipment [Line Items]  
Estimated useful life of property, plant and equipment (in years) 40 years
CL&P  
Property, Plant and Equipment [Line Items]  
Distribution - Electric 35 years 3 months 18 days
Transmission - Electric 37 years 1 month 6 days
NSTAR Electric  
Property, Plant and Equipment [Line Items]  
Distribution - Electric 34 years 6 months
Transmission - Electric 45 years 3 months 18 days
Solar 22 years 9 months 18 days
PSNH  
Property, Plant and Equipment [Line Items]  
Distribution - Electric 29 years 7 months 6 days
Transmission - Electric 41 years 4 months 24 days