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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
 12 Months Ended
Dec. 31, 2024
USD ($)
project
regulatedUtility
customer
Dec. 31, 2023
USD ($)
Dec. 31, 2022
USD ($)
Summary of Accounting Policies [Line Items]      
Number of electric and natural gas customers | customer 4,600,000    
Number of offshore wind projects | project 3    
Goodwill $ 3,571,333,000 $ 4,532,100,000 $ 4,522,600,000
Charitable contributions $ 0 20,000,000 $ 8,000,000.0
Offshore Wind Business      
Summary of Accounting Policies [Line Items]      
Ownership interest (in percent) 50.00%    
Tax Equity      
Summary of Accounting Policies [Line Items]      
Ownership interest (in percent) 50.00%    
Energy Relief Fund      
Summary of Accounting Policies [Line Items]      
Restricted cash, current $ 20,000,000 20,000,000  
Restricted cash, noncurrent $ 5,900,000 14,100,000  
CL&P      
Summary of Accounting Policies [Line Items]      
Period of accounts receivable recoverable under financial or medical duress 180 days    
Maximum loans receivable outstanding $ 70,000,000    
Loans transferred receivable current 9,400,000 8,500,000  
Loans transferred receivable non-current $ 17,300,000 $ 14,500,000  
Yankee Gas Services Company      
Summary of Accounting Policies [Line Items]      
Period of accounts receivable recoverable under financial or medical duress 90 days    
Connecticut, Massachusetts and New Hampshire      
Summary of Accounting Policies [Line Items]      
Number of regulated utilities | regulatedUtility 12