REVENUES (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 2,515,300	$ 2,625,600	$ 5,792,100	$ 6,377,500
Alternative Revenue Programs	13,500	(2,700)	62,600	34,200
Other Revenues	4,700	6,400	11,400	13,300
Operating Revenues	2,533,522	2,629,342	5,866,097	6,424,985
CL&P
Disaggregation of Revenue [Line Items]
Operating Revenues	964,623	1,034,148	2,085,914	2,373,054
NSTAR Electric
Disaggregation of Revenue [Line Items]
Operating Revenues	845,068	818,968	1,792,683	1,775,251
PSNH
Disaggregation of Revenue [Line Items]
Operating Revenues	287,311	350,070	613,427	770,225
Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	2,206,300	2,341,700	5,110,700	5,688,800
Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,269,400	1,379,500	3,061,300	3,449,000
Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	816,300	839,000	1,785,300	1,961,900
Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	120,600	123,200	264,100	277,900
Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	116,800	99,200	229,300	209,000
Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	168,000	153,100	392,500	420,300
Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	24,200	31,600	59,600	59,400
Operating Segments | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,112,000	1,124,200	2,362,900	2,576,000
Alternative Revenue Programs	23,900	52,600	51,300	77,300
Other Revenues	1,500	2,500	4,300	4,700
Operating Segments | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,006,000	961,100	2,103,100	2,065,500
Alternative Revenue Programs	4,200	(5,000)	12,000	(14,500)
Other Revenues	1,600	1,800	3,600	4,300
Operating Segments | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	348,100	375,600	722,000	836,700
Alternative Revenue Programs	3,400	21,900	11,000	31,500
Other Revenues	600	700	1,400	1,700
Operating Segments | Total Retail Tariff Sales Revenues | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	794,300	880,000	1,706,800	1,971,400
Operating Segments | Total Retail Tariff Sales Revenues | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	764,800	748,800	1,630,400	1,633,600
Operating Segments | Total Retail Tariff Sales Revenues | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	241,800	290,700	513,400	655,900
Operating Segments | Residential | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	513,700	593,700	1,140,600	1,355,900
Operating Segments | Residential | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	380,200	370,500	842,400	838,300
Operating Segments | Residential | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	133,600	178,000	298,600	412,000
Operating Segments | Commercial | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	248,000	255,000	500,400	550,300
Operating Segments | Commercial | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	354,400	347,200	727,900	731,500
Operating Segments | Commercial | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	81,100	90,200	163,100	198,800
Operating Segments | Industrial | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	32,600	31,300	65,800	65,200
Operating Segments | Industrial | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	30,200	31,100	60,100	63,800
Operating Segments | Industrial | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	27,100	22,500	51,700	45,100
Operating Segments | Wholesale Transmission Revenues | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	218,800	172,500	419,500	368,300
Operating Segments | Wholesale Transmission Revenues | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	200,900	166,900	389,700	334,700
Operating Segments | Wholesale Transmission Revenues | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	93,200	63,600	177,800	135,100
Operating Segments | Wholesale Market Sales Revenues | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	97,400	62,900	218,600	217,600
Operating Segments | Wholesale Market Sales Revenues | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	27,000	32,500	58,600	73,600
Operating Segments | Wholesale Market Sales Revenues | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	7,600	16,900	20,100	38,400
Operating Segments | Other Revenues from Contracts with Customers | CL&P
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,500	8,800	18,000	18,700
Operating Segments | Other Revenues from Contracts with Customers | NSTAR Electric
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	13,300	12,900	24,400	23,600
Operating Segments | Other Revenues from Contracts with Customers | PSNH
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	5,500	4,400	10,700	7,300
Other
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	395,200	408,800	838,800	822,700
Alternative Revenue Programs	0	0	0	0
Other Revenues	0	0	0	0
Operating Revenues	395,200	408,800	838,800	822,700
Other | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Other | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	395,200	408,800	838,800	822,700
Eliminations
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(797,300)	(715,500)	(1,607,200)	(1,459,400)
Alternative Revenue Programs	(15,800)	(65,700)	(42,600)	(82,700)
Other Revenues	0	0	0	0
Operating Revenues	(813,100)	(781,200)	(1,649,800)	(1,542,100)
Eliminations | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(7,500)	(5,900)	(14,300)	(12,000)
Eliminations | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Eliminations | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(1,500)	(1,200)	(3,200)	(2,300)
Eliminations | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(6,000)	(4,700)	(11,100)	(9,700)
Eliminations | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(396,100)	(303,800)	(757,700)	(629,100)
Eliminations | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Eliminations | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	(393,700)	(405,800)	(835,200)	(818,300)
Consolidations Eliminations | CL&P
Disaggregation of Revenue [Line Items]
Operating Revenues	(172,800)	(145,200)	(332,600)	(284,900)
Consolidations Eliminations | NSTAR Electric
Disaggregation of Revenue [Line Items]
Operating Revenues	(166,700)	(138,900)	(326,000)	(280,000)
Consolidations Eliminations | PSNH
Disaggregation of Revenue [Line Items]
Operating Revenues	(64,800)	(48,100)	(121,000)	(99,700)
Electric Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,948,700	2,052,500	4,191,700	4,629,600
Alternative Revenue Programs	14,000	(3,000)	27,300	3,100
Other Revenues	3,600	4,900	9,000	10,300
Operating Revenues	1,966,300	2,054,400	4,228,000	4,643,000
Electric Distribution | Operating Segments | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,800,600	1,919,200	3,849,900	4,260,800
Electric Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,027,500	1,142,200	2,281,600	2,606,200
Electric Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	683,200	692,100	1,390,700	1,480,500
Electric Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	89,900	84,900	177,600	174,100
Electric Distribution | Operating Segments | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Distribution | Operating Segments | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	132,000	112,300	297,300	329,600
Electric Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	16,100	21,000	44,500	39,200
Natural Gas Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	392,600	411,100	1,266,400	1,427,900
Alternative Revenue Programs	200	(3,100)	31,600	24,300
Other Revenues	700	1,100	1,500	2,100
Operating Revenues	393,500	409,100	1,299,500	1,454,300
Natural Gas Distribution | Operating Segments | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	356,100	370,200	1,170,500	1,336,300
Natural Gas Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	204,100	198,400	711,700	774,900
Natural Gas Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	116,400	129,900	363,400	450,000
Natural Gas Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	35,600	41,900	95,400	111,400
Natural Gas Distribution | Operating Segments | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Natural Gas Distribution | Operating Segments | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	35,000	39,800	93,300	88,900
Natural Gas Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,500	1,100	2,600	2,700
Electric Transmission | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	516,500	407,500	994,600	847,200
Alternative Revenue Programs	17,500	72,500	47,000	91,200
Other Revenues	100	100	300	400
Operating Revenues	534,100	480,100	1,041,900	938,800
Electric Transmission | Operating Segments | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	512,900	403,000	987,000	838,100
Electric Transmission | Operating Segments | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Electric Transmission | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	3,600	4,500	7,600	9,100
Water Distribution | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	59,600	61,200	107,800	109,500
Alternative Revenue Programs	(2,400)	(3,400)	(700)	(1,700)
Other Revenues	300	300	600	500
Operating Revenues	57,500	58,100	107,700	108,300
Water Distribution | Operating Segments | Total Retail Tariff Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	57,100	58,200	104,600	103,700
Water Distribution | Operating Segments | Residential
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	37,800	38,900	68,000	67,900
Water Distribution | Operating Segments | Commercial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	18,200	18,200	34,400	33,700
Water Distribution | Operating Segments | Industrial
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,100	1,100	2,200	2,100
Water Distribution | Operating Segments | Wholesale Transmission Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	0	0	0	0
Water Distribution | Operating Segments | Wholesale Market Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	1,000	1,000	1,900	1,800
Water Distribution | Operating Segments | Other Revenues from Contracts with Customers
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	$ 1,500	$ 2,000	$ 1,300	$ 4,000