REVENUES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	May 06, 2021	Mar. 31, 2021
Loss Contingencies [Line Items]
Revenue	$ 12,270,200	$ 9,815,000	$ 8,766,500
Loss related to litigation settlement	(72,041)	81,274	0
Lease revenue	$ 4,000	$ 4,800	$ 4,300
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Income, Net	Other Income, Net	Other Income, Net
CL&P
Loss Contingencies [Line Items]
Loss related to litigation settlement	$ (72,041)	$ 81,274	$ 0
Lease revenue	800	800	800
NSTAR Electric
Loss Contingencies [Line Items]
Lease revenue	2,500	3,100	2,700
Amortization of/(Reserve for) Revenues Subject to Refund
Loss Contingencies [Line Items]
Revenue	72,000	(78,700)
Operating Segments | CL&P
Loss Contingencies [Line Items]
Revenue	5,343,200	4,238,900	4,044,700
Operating Segments | NSTAR Electric
Loss Contingencies [Line Items]
Revenue	4,127,300	3,541,600	3,327,500
Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund | CL&P
Loss Contingencies [Line Items]
Revenue	72,700	(76,100)	0
Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund | NSTAR Electric
Loss Contingencies [Line Items]
Revenue	0	0	$ 0
Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Loss related to litigation settlement	103,600
Unfavorable Regulatory Action | CL&P
Loss Contingencies [Line Items]
Loss contingency, estimate of possible earnings impact, non-compliance with performance standards				$ 28,400	$ 28,400
Unfavorable Regulatory Action | Operating Segments | Amortization of/(Reserve for) Revenues Subject to Refund | CL&P
Loss Contingencies [Line Items]
Revenue		93,400
Sales | Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Loss related to litigation settlement	$ 65,000
Sales | Unfavorable Regulatory Action | CL&P
Loss Contingencies [Line Items]
Loss related to litigation settlement		$ 65,000