EMPLOYEE BENEFITS - Schedule of Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 59.9	$ 55.5	$ 49.4
CL&P
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	7.7	7.0	6.6
NSTAR Electric
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	12.8	12.2	11.8
PSNH
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 4.8	$ 4.3	$ 4.1