EMPLOYEE BENEFITS - Schedule of Funded Status (Details) - Pension and SERP - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 4,856.5	$ 4,617.1
CL&P
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	981.5	953.9
NSTAR Electric
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	992.2	969.5
PSNH
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 513.1	$ 507.4