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ACQUISITION OF ASSETS OF COLUMBIA GAS OF MASSACHUSETTS - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Oct. 09, 2020
Dec. 31, 2020
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Business Acquisition [Line Items]          
Operating revenues         $ 154.8
Pre-tax income         13.9
TSA          
Business Acquisition [Line Items]          
TSA and pre-TSA costs     $ 7.9 $ 21.4 15.9
Energy efficiency expense   $ 2.0      
CMA          
Business Acquisition [Line Items]          
Consideration transferred $ 1,100.0        
Target working capital amount $ 68.6        
Operating revenues         $ 9,273.0