LEASES - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Lessee, Lease, Description [Line Items]
Lease agreements executed but not yet commenced	$ 11.5
Decrease in right of use asset	$ 7.5
Minimum
Lessee, Lease, Description [Line Items]
Renewal period	1 year
Maximum
Lessee, Lease, Description [Line Items]
Renewal period	20 years
CL&P
Lessee, Lease, Description [Line Items]
Lease agreements executed but not yet commenced	$ 7.0
CL&P | Minimum
Lessee, Lease, Description [Line Items]
Renewal period	1 year
CL&P | Maximum
Lessee, Lease, Description [Line Items]
Renewal period	20 years
NSTAR Electric
Lessee, Lease, Description [Line Items]
Lease agreements executed but not yet commenced	$ 4.5
NSTAR Electric | Minimum
Lessee, Lease, Description [Line Items]
Renewal period	1 year
NSTAR Electric | Maximum
Lessee, Lease, Description [Line Items]
Renewal period	20 years
PSNH | Minimum
Lessee, Lease, Description [Line Items]
Renewal period	1 year
PSNH | Maximum
Lessee, Lease, Description [Line Items]
Renewal period	20 years