PROPERTY, PLANT AND EQUIPMENT AND ACCUMULATED DEPRECIATION - Investment in Utility Property, Plant and Equipment By Asset (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Distribution - Electric	$ 18,326,200	$ 17,679,100
Distribution - Natural Gas	7,443,800	6,694,800
Transmission - Electric	13,709,300	12,882,400
Distribution - Water	2,112,600	1,900,900
Solar	200,800	200,900
Utility	41,792,700	39,358,100
Other	1,738,100	1,469,500
Property, Plant and Equipment, Gross	43,530,800	40,827,600
Less:  Accumulated Depreciation
Utility	(9,167,400)	(8,885,200)
Other	(706,100)	(580,100)
Total Accumulated Depreciation	(9,873,500)	(9,465,300)
Property, Plant and Equipment, Net	33,657,300	31,362,300
Construction Work in Progress	2,455,500	2,015,400
Total Property, Plant and Equipment, Net	36,112,820	33,377,650
CL&P
Property, Plant and Equipment [Line Items]
Distribution - Electric	7,370,100	7,117,600
Transmission - Electric	6,165,100	5,859,000
Solar	0	0
Property, Plant and Equipment, Gross	13,535,200	12,976,600
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(2,567,100)	(2,572,100)
Property, Plant and Equipment, Net	10,968,100	10,404,500
Construction Work in Progress	498,900	399,000
Total Property, Plant and Equipment, Net	11,467,024	10,803,543
NSTAR Electric
Property, Plant and Equipment [Line Items]
Distribution - Electric	8,410,000	8,105,500
Transmission - Electric	5,333,800	5,090,500
Solar	200,800	200,900
Property, Plant and Equipment, Gross	13,944,600	13,396,900
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(3,381,200)	(3,227,300)
Property, Plant and Equipment, Net	10,563,400	10,169,600
Construction Work in Progress	1,063,600	707,000
Total Property, Plant and Equipment, Net	11,626,968	10,876,614
PSNH
Property, Plant and Equipment [Line Items]
Distribution - Electric	2,586,400	2,496,200
Transmission - Electric	2,212,000	1,934,600
Solar	0	0
Property, Plant and Equipment, Gross	4,798,400	4,430,800
Less:  Accumulated Depreciation
Total Accumulated Depreciation	(912,300)	(908,400)
Property, Plant and Equipment, Net	3,886,100	3,522,400
Construction Work in Progress	174,100	134,100
Total Property, Plant and Equipment, Net	$ 4,060,224	$ 3,656,462