EMPLOYEE BENEFITS - Schedule of Funded Status (Details) - Pension and SERP - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 4,911.6	$ 6,337.3
CL&P
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	960.7	1,241.1
NSTAR Electric
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	1,055.1	1,376.1
PSNH
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 516.9	$ 670.3