EMPLOYEE BENEFITS - Schedule of Defined Contribution Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 68.6	$ 76.2	$ 67.3
CL&P
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	9.3	10.6	9.0
NSTAR Electric
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	15.7	15.4	13.7
PSNH
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost recognized	$ 5.1	$ 6.0	$ 5.4