PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Summary of Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	$ 18,984,300	$ 18,326,200
Distribution - Natural Gas	7,667,000	7,443,800
Transmission - Electric	14,106,900	13,709,300
Distribution - Water	2,158,900	2,112,600
Solar	200,800	200,800
Utility	43,117,900	41,792,700
Other	1,856,000	1,738,100
Property, Plant and Equipment, Gross	44,973,900	43,530,800
Less:  Accumulated Depreciation
Utility	(9,483,300)	(9,167,400)
Other	(783,400)	(706,100)
Total Accumulated Depreciation	(10,266,700)	(9,873,500)
Property, Plant and Equipment, Net	34,707,200	33,657,300
Construction Work in Progress	2,871,000	2,455,500
Total Property, Plant and Equipment, Net	37,578,203	36,112,820
CL&P
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	7,652,700	7,370,100
Transmission - Electric	6,327,600	6,165,100
Solar	0	0
Property, Plant and Equipment, Gross	13,980,300	13,535,200
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(2,640,200)	(2,567,100)
Property, Plant and Equipment, Net	11,340,100	10,968,100
Construction Work in Progress	478,700	498,900
Total Property, Plant and Equipment, Net	11,818,824	11,467,024
NSTAR Electric
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	8,672,300	8,410,000
Transmission - Electric	5,457,900	5,333,800
Solar	200,800	200,800
Property, Plant and Equipment, Gross	14,331,000	13,944,600
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(3,480,800)	(3,381,200)
Property, Plant and Equipment, Net	10,850,200	10,563,400
Construction Work in Progress	1,259,200	1,063,600
Total Property, Plant and Equipment, Net	12,109,368	11,626,968
PSNH
Public Utility, Property, Plant and Equipment [Line Items]
Distribution - Electric	2,699,600	2,586,400
Transmission - Electric	2,323,100	2,212,000
Solar	0	0
Property, Plant and Equipment, Gross	5,022,700	4,798,400
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(956,600)	(912,300)
Property, Plant and Equipment, Net	4,066,100	3,886,100
Construction Work in Progress	222,500	174,100
Total Property, Plant and Equipment, Net	$ 4,288,606	$ 4,060,224