COMMITMENTS AND CONTINGENCIES - Schedule of Number of Sites and Reserves (Details) - site	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Loss Contingencies [Line Items]
Number of Sites	65	59
CL&P
Loss Contingencies [Line Items]
Number of Sites	16	13
NSTAR Electric
Loss Contingencies [Line Items]
Number of Sites	12	10
PSNH
Loss Contingencies [Line Items]
Number of Sites	8	8